[PATCH v3 0/5] kvm "virtio pmem" device

[PATCH v3 0/5] kvm "virtio pmem" device

[Pankaj Gupta]

 This patch series has implementation for "virtio pmem". 
 "virtio pmem" is fake persistent memory(nvdimm) in guest 
 which allows to bypass the guest page cache. This also
 implements a VIRTIO based asynchronous flush mechanism.  
 
 Sharing guest kernel driver in this patchset with the 
 changes suggested in v2. Tested with Qemu side device 
 emulation for virtio-pmem [6]. 
 
 Details of project idea for 'virtio pmem' flushing interface 
 is shared [3] & [4].

 Implementation is divided into two parts:
 New virtio pmem guest driver and qemu code changes for new 
 virtio pmem paravirtualized device.

1. Guest virtio-pmem kernel driver
---------------------------------
   - Reads persistent memory range from paravirt device and 
     registers with 'nvdimm_bus'.  
   - 'nvdimm/pmem' driver uses this information to allocate 
     persistent memory region and setup filesystem operations 
     to the allocated memory. 
   - virtio pmem driver implements asynchronous flushing 
     interface to flush from guest to host.

2. Qemu virtio-pmem device
---------------------------------
   - Creates virtio pmem device and exposes a memory range to 
     KVM guest. 
   - At host side this is file backed memory which acts as 
     persistent memory. 
   - Qemu side flush uses aio thread pool API's and virtio 
     for asynchronous guest multi request handling. 

   David Hildenbrand CCed also posted a modified version[6] of 
   qemu virtio-pmem code based on updated Qemu memory device API. 

 Virtio-pmem errors handling:
 ----------------------------------------
  Checked behaviour of virtio-pmem for below types of errors
  Need suggestions on expected behaviour for handling these errors?

  - Hardware Errors: Uncorrectable recoverable Errors: 
  a] virtio-pmem: 
    - As per current logic if error page belongs to Qemu process, 
      host MCE handler isolates(hwpoison) that page and send SIGBUS. 
      Qemu SIGBUS handler injects exception to KVM guest. 
    - KVM guest then isolates the page and send SIGBUS to guest 
      userspace process which has mapped the page. 
  
  b] Existing implementation for ACPI pmem driver: 
    - Handles such errors with MCE notifier and creates a list 
      of bad blocks. Read/direct access DAX operation return EIO 
      if accessed memory page fall in bad block list.
    - It also starts backgound scrubbing.  
    - Similar functionality can be reused in virtio-pmem with MCE 
      notifier but without scrubbing(no ACPI/ARS)? Need inputs to 
      confirm if this behaviour is ok or needs any change?

Changes from PATCH v2: [1]
- Disable MAP_SYNC for ext4 & XFS filesystems - [Dan] 
- Use name 'virtio pmem' in place of 'fake dax' 

Changes from PATCH v1: [2]
- 0-day build test for build dependency on libnvdimm 

 Changes suggested by - [Dan Williams]
- Split the driver into two parts virtio & pmem  
- Move queuing of async block request to block layer
- Add "sync" parameter in nvdimm_flush function
- Use indirect call for nvdimm_flush
- Don’t move declarations to common global header e.g nd.h
- nvdimm_flush() return 0 or -EIO if it fails
- Teach nsio_rw_bytes() that the flush can fail
- Rename nvdimm_flush() to generic_nvdimm_flush()
- Use 'nd_region->provider_data' for long dereferencing
- Remove virtio_pmem_freeze/restore functions
- Remove BSD license text with SPDX license text

- Add might_sleep() in virtio_pmem_flush - [Luiz]
- Make spin_lock_irqsave() narrow

Changes from RFC v3
- Rebase to latest upstream - Luiz
- Call ndregion->flush in place of nvdimm_flush- Luiz
- kmalloc return check - Luiz
- virtqueue full handling - Stefan
- Don't map entire virtio_pmem_req to device - Stefan
- request leak, correct sizeof req- Stefan
- Move declaration to virtio_pmem.c

Changes from RFC v2:
- Add flush function in the nd_region in place of switching
  on a flag - Dan & Stefan
- Add flush completion function with proper locking and wait
  for host side flush completion - Stefan & Dan
- Keep userspace API in uapi header file - Stefan, MST
- Use LE fields & New device id - MST
- Indentation & spacing suggestions - MST & Eric
- Remove extra header files & add licensing - Stefan

Changes from RFC v1:
- Reuse existing 'pmem' code for registering persistent 
  memory and other operations instead of creating an entirely 
  new block driver.
- Use VIRTIO driver to register memory information with 
  nvdimm_bus and create region_type accordingly. 
- Call VIRTIO flush from existing pmem driver.

Pankaj Gupta (5):
   libnvdimm: nd_region flush callback support
   virtio-pmem: Add virtio-pmem guest driver
   libnvdimm: add nd_region buffered dax_dev flag
   ext4: disable map_sync for virtio pmem
   xfs: disable map_sync for virtio pmem

[2] https://lkml.org/lkml/2018/8/31/407
[3] https://www.spinics.net/lists/kvm/msg149761.html
[4] https://www.spinics.net/lists/kvm/msg153095.html  
[5] https://lkml.org/lkml/2018/8/31/413
[6] https://marc.info/?l=qemu-devel&m=153555721901824&w=2

 drivers/acpi/nfit/core.c         |    4 -
 drivers/dax/super.c              |   17 +++++
 drivers/nvdimm/claim.c           |    6 +
 drivers/nvdimm/nd.h              |    1 
 drivers/nvdimm/pmem.c            |   15 +++-
 drivers/nvdimm/region_devs.c     |   45 +++++++++++++-
 drivers/nvdimm/virtio_pmem.c     |   84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |   10 +++
 drivers/virtio/Makefile          |    1 
 drivers/virtio/pmem.c            |  125 +++++++++++++++++++++++++++++++++++++++
 fs/ext4/file.c                   |   11 +++
 fs/xfs/xfs_file.c                |    8 ++
 include/linux/dax.h              |    9 ++
 include/linux/libnvdimm.h        |   11 +++
 include/linux/virtio_pmem.h      |   60 ++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |    1 
 include/uapi/linux/virtio_pmem.h |   10 +++
 17 files changed, 406 insertions(+), 12 deletions(-)

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

[PATCH v3 0/5] kvm "virtio pmem" device

[Pankaj Gupta]

 This patch series has implementation for "virtio pmem". 
 "virtio pmem" is fake persistent memory(nvdimm) in guest 
 which allows to bypass the guest page cache. This also
 implements a VIRTIO based asynchronous flush mechanism.  
 
 Sharing guest kernel driver in this patchset with the 
 changes suggested in v2. Tested with Qemu side device 
 emulation for virtio-pmem [6]. 
 
 Details of project idea for 'virtio pmem' flushing interface 
 is shared [3] & [4].

 Implementation is divided into two parts:
 New virtio pmem guest driver and qemu code changes for new 
 virtio pmem paravirtualized device.

1. Guest virtio-pmem kernel driver
---------------------------------
   - Reads persistent memory range from paravirt device and 
     registers with 'nvdimm_bus'.  
   - 'nvdimm/pmem' driver uses this information to allocate 
     persistent memory region and setup filesystem operations 
     to the allocated memory. 
   - virtio pmem driver implements asynchronous flushing 
     interface to flush from guest to host.

2. Qemu virtio-pmem device
---------------------------------
   - Creates virtio pmem device and exposes a memory range to 
     KVM guest. 
   - At host side this is file backed memory which acts as 
     persistent memory. 
   - Qemu side flush uses aio thread pool API's and virtio 
     for asynchronous guest multi request handling. 

   David Hildenbrand CCed also posted a modified version[6] of 
   qemu virtio-pmem code based on updated Qemu memory device API. 

 Virtio-pmem errors handling:
 ----------------------------------------
  Checked behaviour of virtio-pmem for below types of errors
  Need suggestions on expected behaviour for handling these errors?

  - Hardware Errors: Uncorrectable recoverable Errors: 
  a] virtio-pmem: 
    - As per current logic if error page belongs to Qemu process, 
      host MCE handler isolates(hwpoison) that page and send SIGBUS. 
      Qemu SIGBUS handler injects exception to KVM guest. 
    - KVM guest then isolates the page and send SIGBUS to guest 
      userspace process which has mapped the page. 
  
  b] Existing implementation for ACPI pmem driver: 
    - Handles such errors with MCE notifier and creates a list 
      of bad blocks. Read/direct access DAX operation return EIO 
      if accessed memory page fall in bad block list.
    - It also starts backgound scrubbing.  
    - Similar functionality can be reused in virtio-pmem with MCE 
      notifier but without scrubbing(no ACPI/ARS)? Need inputs to 
      confirm if this behaviour is ok or needs any change?

Changes from PATCH v2: [1]
- Disable MAP_SYNC for ext4 & XFS filesystems - [Dan] 
- Use name 'virtio pmem' in place of 'fake dax' 

Changes from PATCH v1: [2]
- 0-day build test for build dependency on libnvdimm 

 Changes suggested by - [Dan Williams]
- Split the driver into two parts virtio & pmem  
- Move queuing of async block request to block layer
- Add "sync" parameter in nvdimm_flush function
- Use indirect call for nvdimm_flush
- Don’t move declarations to common global header e.g nd.h
- nvdimm_flush() return 0 or -EIO if it fails
- Teach nsio_rw_bytes() that the flush can fail
- Rename nvdimm_flush() to generic_nvdimm_flush()
- Use 'nd_region->provider_data' for long dereferencing
- Remove virtio_pmem_freeze/restore functions
- Remove BSD license text with SPDX license text

- Add might_sleep() in virtio_pmem_flush - [Luiz]
- Make spin_lock_irqsave() narrow

Changes from RFC v3
- Rebase to latest upstream - Luiz
- Call ndregion->flush in place of nvdimm_flush- Luiz
- kmalloc return check - Luiz
- virtqueue full handling - Stefan
- Don't map entire virtio_pmem_req to device - Stefan
- request leak, correct sizeof req- Stefan
- Move declaration to virtio_pmem.c

Changes from RFC v2:
- Add flush function in the nd_region in place of switching
  on a flag - Dan & Stefan
- Add flush completion function with proper locking and wait
  for host side flush completion - Stefan & Dan
- Keep userspace API in uapi header file - Stefan, MST
- Use LE fields & New device id - MST
- Indentation & spacing suggestions - MST & Eric
- Remove extra header files & add licensing - Stefan

Changes from RFC v1:
- Reuse existing 'pmem' code for registering persistent 
  memory and other operations instead of creating an entirely 
  new block driver.
- Use VIRTIO driver to register memory information with 
  nvdimm_bus and create region_type accordingly. 
- Call VIRTIO flush from existing pmem driver.

Pankaj Gupta (5):
   libnvdimm: nd_region flush callback support
   virtio-pmem: Add virtio-pmem guest driver
   libnvdimm: add nd_region buffered dax_dev flag
   ext4: disable map_sync for virtio pmem
   xfs: disable map_sync for virtio pmem

[2] https://lkml.org/lkml/2018/8/31/407
[3] https://www.spinics.net/lists/kvm/msg149761.html
[4] https://www.spinics.net/lists/kvm/msg153095.html  
[5] https://lkml.org/lkml/2018/8/31/413
[6] https://marc.info/?l=qemu-devel&m=153555721901824&w=2

 drivers/acpi/nfit/core.c         |    4 -
 drivers/dax/super.c              |   17 +++++
 drivers/nvdimm/claim.c           |    6 +
 drivers/nvdimm/nd.h              |    1 
 drivers/nvdimm/pmem.c            |   15 +++-
 drivers/nvdimm/region_devs.c     |   45 +++++++++++++-
 drivers/nvdimm/virtio_pmem.c     |   84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |   10 +++
 drivers/virtio/Makefile          |    1 
 drivers/virtio/pmem.c            |  125 +++++++++++++++++++++++++++++++++++++++
 fs/ext4/file.c                   |   11 +++
 fs/xfs/xfs_file.c                |    8 ++
 include/linux/dax.h              |    9 ++
 include/linux/libnvdimm.h        |   11 +++
 include/linux/virtio_pmem.h      |   60 ++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |    1 
 include/uapi/linux/virtio_pmem.h |   10 +++
 17 files changed, 406 insertions(+), 12 deletions(-)

[Qemu-devel] [PATCH v3 0/5] kvm "virtio pmem" device

[Pankaj Gupta]

 This patch series has implementation for "virtio pmem". 
 "virtio pmem" is fake persistent memory(nvdimm) in guest 
 which allows to bypass the guest page cache. This also
 implements a VIRTIO based asynchronous flush mechanism.  
 
 Sharing guest kernel driver in this patchset with the 
 changes suggested in v2. Tested with Qemu side device 
 emulation for virtio-pmem [6]. 
 
 Details of project idea for 'virtio pmem' flushing interface 
 is shared [3] & [4].

 Implementation is divided into two parts:
 New virtio pmem guest driver and qemu code changes for new 
 virtio pmem paravirtualized device.

1. Guest virtio-pmem kernel driver
---------------------------------
   - Reads persistent memory range from paravirt device and 
     registers with 'nvdimm_bus'.  
   - 'nvdimm/pmem' driver uses this information to allocate 
     persistent memory region and setup filesystem operations 
     to the allocated memory. 
   - virtio pmem driver implements asynchronous flushing 
     interface to flush from guest to host.

2. Qemu virtio-pmem device
---------------------------------
   - Creates virtio pmem device and exposes a memory range to 
     KVM guest. 
   - At host side this is file backed memory which acts as 
     persistent memory. 
   - Qemu side flush uses aio thread pool API's and virtio 
     for asynchronous guest multi request handling. 

   David Hildenbrand CCed also posted a modified version[6] of 
   qemu virtio-pmem code based on updated Qemu memory device API. 

 Virtio-pmem errors handling:
 ----------------------------------------
  Checked behaviour of virtio-pmem for below types of errors
  Need suggestions on expected behaviour for handling these errors?

  - Hardware Errors: Uncorrectable recoverable Errors: 
  a] virtio-pmem: 
    - As per current logic if error page belongs to Qemu process, 
      host MCE handler isolates(hwpoison) that page and send SIGBUS. 
      Qemu SIGBUS handler injects exception to KVM guest. 
    - KVM guest then isolates the page and send SIGBUS to guest 
      userspace process which has mapped the page. 
  
  b] Existing implementation for ACPI pmem driver: 
    - Handles such errors with MCE notifier and creates a list 
      of bad blocks. Read/direct access DAX operation return EIO 
      if accessed memory page fall in bad block list.
    - It also starts backgound scrubbing.  
    - Similar functionality can be reused in virtio-pmem with MCE 
      notifier but without scrubbing(no ACPI/ARS)? Need inputs to 
      confirm if this behaviour is ok or needs any change?

Changes from PATCH v2: [1]
- Disable MAP_SYNC for ext4 & XFS filesystems - [Dan] 
- Use name 'virtio pmem' in place of 'fake dax' 

Changes from PATCH v1: [2]
- 0-day build test for build dependency on libnvdimm 

 Changes suggested by - [Dan Williams]
- Split the driver into two parts virtio & pmem  
- Move queuing of async block request to block layer
- Add "sync" parameter in nvdimm_flush function
- Use indirect call for nvdimm_flush
- Don’t move declarations to common global header e.g nd.h
- nvdimm_flush() return 0 or -EIO if it fails
- Teach nsio_rw_bytes() that the flush can fail
- Rename nvdimm_flush() to generic_nvdimm_flush()
- Use 'nd_region->provider_data' for long dereferencing
- Remove virtio_pmem_freeze/restore functions
- Remove BSD license text with SPDX license text

- Add might_sleep() in virtio_pmem_flush - [Luiz]
- Make spin_lock_irqsave() narrow

Changes from RFC v3
- Rebase to latest upstream - Luiz
- Call ndregion->flush in place of nvdimm_flush- Luiz
- kmalloc return check - Luiz
- virtqueue full handling - Stefan
- Don't map entire virtio_pmem_req to device - Stefan
- request leak, correct sizeof req- Stefan
- Move declaration to virtio_pmem.c

Changes from RFC v2:
- Add flush function in the nd_region in place of switching
  on a flag - Dan & Stefan
- Add flush completion function with proper locking and wait
  for host side flush completion - Stefan & Dan
- Keep userspace API in uapi header file - Stefan, MST
- Use LE fields & New device id - MST
- Indentation & spacing suggestions - MST & Eric
- Remove extra header files & add licensing - Stefan

Changes from RFC v1:
- Reuse existing 'pmem' code for registering persistent 
  memory and other operations instead of creating an entirely 
  new block driver.
- Use VIRTIO driver to register memory information with 
  nvdimm_bus and create region_type accordingly. 
- Call VIRTIO flush from existing pmem driver.

Pankaj Gupta (5):
   libnvdimm: nd_region flush callback support
   virtio-pmem: Add virtio-pmem guest driver
   libnvdimm: add nd_region buffered dax_dev flag
   ext4: disable map_sync for virtio pmem
   xfs: disable map_sync for virtio pmem

[2] https://lkml.org/lkml/2018/8/31/407
[3] https://www.spinics.net/lists/kvm/msg149761.html
[4] https://www.spinics.net/lists/kvm/msg153095.html  
[5] https://lkml.org/lkml/2018/8/31/413
[6] https://marc.info/?l=qemu-devel&m=153555721901824&w=2

 drivers/acpi/nfit/core.c         |    4 -
 drivers/dax/super.c              |   17 +++++
 drivers/nvdimm/claim.c           |    6 +
 drivers/nvdimm/nd.h              |    1 
 drivers/nvdimm/pmem.c            |   15 +++-
 drivers/nvdimm/region_devs.c     |   45 +++++++++++++-
 drivers/nvdimm/virtio_pmem.c     |   84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |   10 +++
 drivers/virtio/Makefile          |    1 
 drivers/virtio/pmem.c            |  125 +++++++++++++++++++++++++++++++++++++++
 fs/ext4/file.c                   |   11 +++
 fs/xfs/xfs_file.c                |    8 ++
 include/linux/dax.h              |    9 ++
 include/linux/libnvdimm.h        |   11 +++
 include/linux/virtio_pmem.h      |   60 ++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |    1 
 include/uapi/linux/virtio_pmem.h |   10 +++
 17 files changed, 406 insertions(+), 12 deletions(-)

[PATCH v3 1/5] libnvdimm: nd_region flush callback support

[Pankaj Gupta]

This patch adds functionality to perform flush from guest
to host over VIRTIO. We are registering a callback based
on 'nd_region' type. virtio_pmem driver requires this special
flush function. For rest of the region types we are registering
existing flush function. Report error returned by host fsync
failure to userspace.

This also handles asynchronous flush requests from the block layer
by creating a child bio and chaining it with parent bio.

Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 drivers/acpi/nfit/core.c     |  4 ++--
 drivers/nvdimm/claim.c       |  6 ++++--
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        | 12 ++++++++----
 drivers/nvdimm/region_devs.c | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/libnvdimm.h    |  5 ++++-
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b072cfc..f154852 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2234,7 +2234,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->addr.base + offset);
-	nvdimm_flush(nfit_blk->nd_region);
+	nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
 		readq(mmio->addr.base + offset);
@@ -2283,7 +2283,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 	}
 
 	if (rw)
-		nvdimm_flush(nfit_blk->nd_region);
+		nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index fb667bf..a1dfa06 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -263,7 +263,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
 	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
 	sector_t sector = offset >> 9;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	if (unlikely(!size))
 		return 0;
@@ -301,7 +301,9 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	memcpy_flushcache(nsio->addr + offset, buf, size);
-	nvdimm_flush(to_nd_region(ndns->dev.parent));
+	ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL, false);
+	if (ret)
+		rc = ret;
 
 	return rc;
 }
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7..d53a2d1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -160,6 +160,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	struct nd_mapping mapping[0];
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct nd_blk_region {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e29..5d6a4a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -192,6 +192,7 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+	int ret = 0;
 	blk_status_t rc = 0;
 	bool do_acct;
 	unsigned long start;
@@ -201,7 +202,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_PREFLUSH)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -216,7 +217,10 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
+
+	if (ret)
+		bio->bi_status = errno_to_blk_status(ret);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
@@ -528,14 +532,14 @@ static int nd_pmem_remove(struct device *dev)
 		sysfs_put(pmem->bb_state);
 		pmem->bb_state = NULL;
 	}
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 
 	return 0;
 }
 
 static void nd_pmem_shutdown(struct device *dev)
 {
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 }
 
 static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afc..5508727 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -290,7 +290,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
 		return rc;
 	if (!flush)
 		return -EINVAL;
-	nvdimm_flush(nd_region);
+	rc = nvdimm_flush(nd_region, NULL, false);
+	if (rc)
+		return rc;
 
 	return len;
 }
@@ -1065,6 +1067,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	if (ndr_desc->flush)
+		nd_region->flush = ndr_desc->flush;
+	else
+		nd_region->flush = generic_nvdimm_flush;
+
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1105,11 +1112,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async)
+{
+	int rc = 0;
+
+	/* Create child bio for asynchronous flush and chain with
+	 * parent bio. Otherwise directly call nd_region flush.
+	 */
+	if (async && bio->bi_iter.bi_sector != -1) {
+
+		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
+
+		if (!child)
+			return -ENOMEM;
+		bio_copy_dev(child, bio);
+		child->bi_opf = REQ_PREFLUSH;
+		child->bi_iter.bi_sector = -1;
+		bio_chain(child, bio);
+		submit_bio(child);
+	} else {
+		if (nd_region->flush(nd_region))
+			rc = -EIO;
+	}
+
+	return rc;
+}
 /**
  * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  * @nd_region: blk or interleaved pmem region
  */
-void nvdimm_flush(struct nd_region *nd_region)
+int generic_nvdimm_flush(struct nd_region *nd_region)
 {
 	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
 	int i, idx;
@@ -1133,6 +1165,8 @@ void nvdimm_flush(struct nd_region *nd_region)
 		if (ndrd_get_flush_wpq(ndrd, i, 0))
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..b49632c 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -115,6 +115,7 @@ struct nd_mapping_desc {
 	int position;
 };
 
+struct nd_region;
 struct nd_region_desc {
 	struct resource *res;
 	struct nd_mapping_desc *mapping;
@@ -126,6 +127,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct device;
@@ -201,7 +203,8 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async);
+int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3

[PATCH v3 1/5] libnvdimm: nd_region flush callback support

[Pankaj Gupta]

This patch adds functionality to perform flush from guest
to host over VIRTIO. We are registering a callback based
on 'nd_region' type. virtio_pmem driver requires this special
flush function. For rest of the region types we are registering
existing flush function. Report error returned by host fsync
failure to userspace.

This also handles asynchronous flush requests from the block layer
by creating a child bio and chaining it with parent bio.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/acpi/nfit/core.c     |  4 ++--
 drivers/nvdimm/claim.c       |  6 ++++--
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        | 12 ++++++++----
 drivers/nvdimm/region_devs.c | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/libnvdimm.h    |  5 ++++-
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b072cfc..f154852 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2234,7 +2234,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->addr.base + offset);
-	nvdimm_flush(nfit_blk->nd_region);
+	nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
 		readq(mmio->addr.base + offset);
@@ -2283,7 +2283,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 	}
 
 	if (rw)
-		nvdimm_flush(nfit_blk->nd_region);
+		nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index fb667bf..a1dfa06 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -263,7 +263,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
 	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
 	sector_t sector = offset >> 9;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	if (unlikely(!size))
 		return 0;
@@ -301,7 +301,9 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	memcpy_flushcache(nsio->addr + offset, buf, size);
-	nvdimm_flush(to_nd_region(ndns->dev.parent));
+	ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL, false);
+	if (ret)
+		rc = ret;
 
 	return rc;
 }
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7..d53a2d1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -160,6 +160,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	struct nd_mapping mapping[0];
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct nd_blk_region {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e29..5d6a4a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -192,6 +192,7 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+	int ret = 0;
 	blk_status_t rc = 0;
 	bool do_acct;
 	unsigned long start;
@@ -201,7 +202,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_PREFLUSH)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -216,7 +217,10 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
+
+	if (ret)
+		bio->bi_status = errno_to_blk_status(ret);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
@@ -528,14 +532,14 @@ static int nd_pmem_remove(struct device *dev)
 		sysfs_put(pmem->bb_state);
 		pmem->bb_state = NULL;
 	}
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 
 	return 0;
 }
 
 static void nd_pmem_shutdown(struct device *dev)
 {
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 }
 
 static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afc..5508727 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -290,7 +290,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
 		return rc;
 	if (!flush)
 		return -EINVAL;
-	nvdimm_flush(nd_region);
+	rc = nvdimm_flush(nd_region, NULL, false);
+	if (rc)
+		return rc;
 
 	return len;
 }
@@ -1065,6 +1067,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	if (ndr_desc->flush)
+		nd_region->flush = ndr_desc->flush;
+	else
+		nd_region->flush = generic_nvdimm_flush;
+
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1105,11 +1112,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async)
+{
+	int rc = 0;
+
+	/* Create child bio for asynchronous flush and chain with
+	 * parent bio. Otherwise directly call nd_region flush.
+	 */
+	if (async && bio->bi_iter.bi_sector != -1) {
+
+		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
+
+		if (!child)
+			return -ENOMEM;
+		bio_copy_dev(child, bio);
+		child->bi_opf = REQ_PREFLUSH;
+		child->bi_iter.bi_sector = -1;
+		bio_chain(child, bio);
+		submit_bio(child);
+	} else {
+		if (nd_region->flush(nd_region))
+			rc = -EIO;
+	}
+
+	return rc;
+}
 /**
  * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  * @nd_region: blk or interleaved pmem region
  */
-void nvdimm_flush(struct nd_region *nd_region)
+int generic_nvdimm_flush(struct nd_region *nd_region)
 {
 	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
 	int i, idx;
@@ -1133,6 +1165,8 @@ void nvdimm_flush(struct nd_region *nd_region)
 		if (ndrd_get_flush_wpq(ndrd, i, 0))
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..b49632c 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -115,6 +115,7 @@ struct nd_mapping_desc {
 	int position;
 };
 
+struct nd_region;
 struct nd_region_desc {
 	struct resource *res;
 	struct nd_mapping_desc *mapping;
@@ -126,6 +127,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct device;
@@ -201,7 +203,8 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async);
+int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3

[Qemu-devel] [PATCH v3 1/5] libnvdimm: nd_region flush callback support

[Pankaj Gupta]

This patch adds functionality to perform flush from guest
to host over VIRTIO. We are registering a callback based
on 'nd_region' type. virtio_pmem driver requires this special
flush function. For rest of the region types we are registering
existing flush function. Report error returned by host fsync
failure to userspace.

This also handles asynchronous flush requests from the block layer
by creating a child bio and chaining it with parent bio.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/acpi/nfit/core.c     |  4 ++--
 drivers/nvdimm/claim.c       |  6 ++++--
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        | 12 ++++++++----
 drivers/nvdimm/region_devs.c | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/libnvdimm.h    |  5 ++++-
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b072cfc..f154852 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2234,7 +2234,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->addr.base + offset);
-	nvdimm_flush(nfit_blk->nd_region);
+	nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
 		readq(mmio->addr.base + offset);
@@ -2283,7 +2283,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 	}
 
 	if (rw)
-		nvdimm_flush(nfit_blk->nd_region);
+		nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index fb667bf..a1dfa06 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -263,7 +263,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
 	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
 	sector_t sector = offset >> 9;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	if (unlikely(!size))
 		return 0;
@@ -301,7 +301,9 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	memcpy_flushcache(nsio->addr + offset, buf, size);
-	nvdimm_flush(to_nd_region(ndns->dev.parent));
+	ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL, false);
+	if (ret)
+		rc = ret;
 
 	return rc;
 }
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7..d53a2d1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -160,6 +160,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	struct nd_mapping mapping[0];
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct nd_blk_region {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e29..5d6a4a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -192,6 +192,7 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+	int ret = 0;
 	blk_status_t rc = 0;
 	bool do_acct;
 	unsigned long start;
@@ -201,7 +202,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_PREFLUSH)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -216,7 +217,10 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
+
+	if (ret)
+		bio->bi_status = errno_to_blk_status(ret);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
@@ -528,14 +532,14 @@ static int nd_pmem_remove(struct device *dev)
 		sysfs_put(pmem->bb_state);
 		pmem->bb_state = NULL;
 	}
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 
 	return 0;
 }
 
 static void nd_pmem_shutdown(struct device *dev)
 {
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 }
 
 static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afc..5508727 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -290,7 +290,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
 		return rc;
 	if (!flush)
 		return -EINVAL;
-	nvdimm_flush(nd_region);
+	rc = nvdimm_flush(nd_region, NULL, false);
+	if (rc)
+		return rc;
 
 	return len;
 }
@@ -1065,6 +1067,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	if (ndr_desc->flush)
+		nd_region->flush = ndr_desc->flush;
+	else
+		nd_region->flush = generic_nvdimm_flush;
+
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1105,11 +1112,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async)
+{
+	int rc = 0;
+
+	/* Create child bio for asynchronous flush and chain with
+	 * parent bio. Otherwise directly call nd_region flush.
+	 */
+	if (async && bio->bi_iter.bi_sector != -1) {
+
+		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
+
+		if (!child)
+			return -ENOMEM;
+		bio_copy_dev(child, bio);
+		child->bi_opf = REQ_PREFLUSH;
+		child->bi_iter.bi_sector = -1;
+		bio_chain(child, bio);
+		submit_bio(child);
+	} else {
+		if (nd_region->flush(nd_region))
+			rc = -EIO;
+	}
+
+	return rc;
+}
 /**
  * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  * @nd_region: blk or interleaved pmem region
  */
-void nvdimm_flush(struct nd_region *nd_region)
+int generic_nvdimm_flush(struct nd_region *nd_region)
 {
 	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
 	int i, idx;
@@ -1133,6 +1165,8 @@ void nvdimm_flush(struct nd_region *nd_region)
 		if (ndrd_get_flush_wpq(ndrd, i, 0))
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..b49632c 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -115,6 +115,7 @@ struct nd_mapping_desc {
 	int position;
 };
 
+struct nd_region;
 struct nd_region_desc {
 	struct resource *res;
 	struct nd_mapping_desc *mapping;
@@ -126,6 +127,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct device;
@@ -201,7 +203,8 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async);
+int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3

[PATCH v3 1/5] libnvdimm: nd_region flush callback support

[Pankaj Gupta]

This patch adds functionality to perform flush from guest
to host over VIRTIO. We are registering a callback based
on 'nd_region' type. virtio_pmem driver requires this special
flush function. For rest of the region types we are registering
existing flush function. Report error returned by host fsync
failure to userspace.

This also handles asynchronous flush requests from the block layer
by creating a child bio and chaining it with parent bio.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/acpi/nfit/core.c     |  4 ++--
 drivers/nvdimm/claim.c       |  6 ++++--
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        | 12 ++++++++----
 drivers/nvdimm/region_devs.c | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/libnvdimm.h    |  5 ++++-
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b072cfc..f154852 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2234,7 +2234,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->addr.base + offset);
-	nvdimm_flush(nfit_blk->nd_region);
+	nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
 		readq(mmio->addr.base + offset);
@@ -2283,7 +2283,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 	}
 
 	if (rw)
-		nvdimm_flush(nfit_blk->nd_region);
+		nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index fb667bf..a1dfa06 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -263,7 +263,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
 	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
 	sector_t sector = offset >> 9;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	if (unlikely(!size))
 		return 0;
@@ -301,7 +301,9 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	memcpy_flushcache(nsio->addr + offset, buf, size);
-	nvdimm_flush(to_nd_region(ndns->dev.parent));
+	ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL, false);
+	if (ret)
+		rc = ret;
 
 	return rc;
 }
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7..d53a2d1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -160,6 +160,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	struct nd_mapping mapping[0];
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct nd_blk_region {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e29..5d6a4a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -192,6 +192,7 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+	int ret = 0;
 	blk_status_t rc = 0;
 	bool do_acct;
 	unsigned long start;
@@ -201,7 +202,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_PREFLUSH)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -216,7 +217,10 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
+
+	if (ret)
+		bio->bi_status = errno_to_blk_status(ret);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
@@ -528,14 +532,14 @@ static int nd_pmem_remove(struct device *dev)
 		sysfs_put(pmem->bb_state);
 		pmem->bb_state = NULL;
 	}
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 
 	return 0;
 }
 
 static void nd_pmem_shutdown(struct device *dev)
 {
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 }
 
 static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afc..5508727 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -290,7 +290,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
 		return rc;
 	if (!flush)
 		return -EINVAL;
-	nvdimm_flush(nd_region);
+	rc = nvdimm_flush(nd_region, NULL, false);
+	if (rc)
+		return rc;
 
 	return len;
 }
@@ -1065,6 +1067,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	if (ndr_desc->flush)
+		nd_region->flush = ndr_desc->flush;
+	else
+		nd_region->flush = generic_nvdimm_flush;
+
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1105,11 +1112,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async)
+{
+	int rc = 0;
+
+	/* Create child bio for asynchronous flush and chain with
+	 * parent bio. Otherwise directly call nd_region flush.
+	 */
+	if (async && bio->bi_iter.bi_sector != -1) {
+
+		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
+
+		if (!child)
+			return -ENOMEM;
+		bio_copy_dev(child, bio);
+		child->bi_opf = REQ_PREFLUSH;
+		child->bi_iter.bi_sector = -1;
+		bio_chain(child, bio);
+		submit_bio(child);
+	} else {
+		if (nd_region->flush(nd_region))
+			rc = -EIO;
+	}
+
+	return rc;
+}
 /**
  * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  * @nd_region: blk or interleaved pmem region
  */
-void nvdimm_flush(struct nd_region *nd_region)
+int generic_nvdimm_flush(struct nd_region *nd_region)
 {
 	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
 	int i, idx;
@@ -1133,6 +1165,8 @@ void nvdimm_flush(struct nd_region *nd_region)
 		if (ndrd_get_flush_wpq(ndrd, i, 0))
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..b49632c 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -115,6 +115,7 @@ struct nd_mapping_desc {
 	int position;
 };
 
+struct nd_region;
 struct nd_region_desc {
 	struct resource *res;
 	struct nd_mapping_desc *mapping;
@@ -126,6 +127,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct device;
@@ -201,7 +203,8 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async);
+int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3

[PATCH v3 2/5] virtio-pmem: Add virtio pmem driver

[Pankaj Gupta]

This patch adds virtio-pmem driver for KVM guest.

Guest reads the persistent memory range information from
Qemu over VIRTIO and registers it on nvdimm_bus. It also
creates a nd_region object with the persistent memory
range information so that existing 'nvdimm/pmem' driver
can reserve this into system memory map. This way
'virtio-pmem' driver uses existing functionality of pmem
driver to register persistent memory compatible for DAX
capable filesystems.

This also provides function to perform guest flush over
VIRTIO from 'pmem' driver when userspace performs flush
on DAX memory range.

Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 drivers/nvdimm/virtio_pmem.c     |  84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |  10 ++++
 drivers/virtio/Makefile          |   1 +
 drivers/virtio/pmem.c            | 124 +++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_pmem.h      |  60 +++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |   1 +
 include/uapi/linux/virtio_pmem.h |  10 ++++
 7 files changed, 290 insertions(+)
 create mode 100644 drivers/nvdimm/virtio_pmem.c
 create mode 100644 drivers/virtio/pmem.c
 create mode 100644 include/linux/virtio_pmem.h
 create mode 100644 include/uapi/linux/virtio_pmem.h

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
new file mode 100644
index 0000000..2a1b1ba
--- /dev/null
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ */
+#include <linux/virtio_pmem.h>
+#include "nd.h"
+
+ /* The interrupt handler */
+void host_ack(struct virtqueue *vq)
+{
+	unsigned int len;
+	unsigned long flags;
+	struct virtio_pmem_request *req, *req_buf;
+	struct virtio_pmem *vpmem = vq->vdev->priv;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+		req->done = true;
+		wake_up(&req->host_acked);
+
+		if (!list_empty(&vpmem->req_list)) {
+			req_buf = list_first_entry(&vpmem->req_list,
+					struct virtio_pmem_request, list);
+			list_del(&vpmem->req_list);
+			req_buf->wq_buf_avail = true;
+			wake_up(&req_buf->wq_buf);
+		}
+	}
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+}
+EXPORT_SYMBOL_GPL(host_ack);
+
+ /* The request submission function */
+int virtio_pmem_flush(struct nd_region *nd_region)
+{
+	int err;
+	unsigned long flags;
+	struct scatterlist *sgs[2], sg, ret;
+	struct virtio_device *vdev = nd_region->provider_data;
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct virtio_pmem_request *req;
+
+	might_sleep();
+	req = kmalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	req->done = req->wq_buf_avail = false;
+	strcpy(req->name, "FLUSH");
+	init_waitqueue_head(&req->host_acked);
+	init_waitqueue_head(&req->wq_buf);
+	sg_init_one(&sg, req->name, strlen(req->name));
+	sgs[0] = &sg;
+	sg_init_one(&ret, &req->ret, sizeof(req->ret));
+	sgs[1] = &ret;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
+	if (err) {
+		dev_err(&vdev->dev, "failed to send command to virtio pmem device\n");
+
+		list_add_tail(&vpmem->req_list, &req->list);
+		spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+		/* When host has read buffer, this completes via host_ack */
+		wait_event(req->wq_buf, req->wq_buf_avail);
+		spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	}
+	virtqueue_kick(vpmem->req_vq);
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+	/* When host has read buffer, this completes via host_ack */
+	wait_event(req->host_acked, req->done);
+	err = req->ret;
+	kfree(req);
+
+	return err;
+};
+EXPORT_SYMBOL_GPL(virtio_pmem_flush);
+MODULE_LICENSE("GPL");
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 3589764..9f634a2 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -42,6 +42,16 @@ config VIRTIO_PCI_LEGACY
 
 	  If unsure, say Y.
 
+config VIRTIO_PMEM
+	tristate "Support for virtio pmem driver"
+	depends on VIRTIO
+	depends on LIBNVDIMM
+	help
+	This driver provides support for virtio based flushing interface
+	for persistent memory range.
+
+	If unsure, say M.
+
 config VIRTIO_BALLOON
 	tristate "Virtio balloon driver"
 	depends on VIRTIO
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 3a2b5c5..143ce91 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VIRTIO_PMEM) += pmem.o ../nvdimm/virtio_pmem.o
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
new file mode 100644
index 0000000..51f5349
--- /dev/null
+++ b/drivers/virtio/pmem.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and registers the virtual pmem device
+ * with libnvdimm core.
+ */
+#include <linux/virtio_pmem.h>
+#include <../../drivers/nvdimm/nd.h>
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+ /* Initialize virt queue */
+static int init_vq(struct virtio_pmem *vpmem)
+{
+	struct virtqueue *vq;
+
+	/* single vq */
+	vpmem->req_vq = vq = virtio_find_single_vq(vpmem->vdev,
+				host_ack, "flush_queue");
+	if (IS_ERR(vq))
+		return PTR_ERR(vq);
+
+	spin_lock_init(&vpmem->pmem_lock);
+	INIT_LIST_HEAD(&vpmem->req_list);
+
+	return 0;
+};
+
+static int virtio_pmem_probe(struct virtio_device *vdev)
+{
+	int err = 0;
+	struct resource res;
+	struct virtio_pmem *vpmem;
+	struct nvdimm_bus *nvdimm_bus;
+	struct nd_region_desc ndr_desc;
+	int nid = dev_to_node(&vdev->dev);
+	struct nd_region *nd_region;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem),
+			GFP_KERNEL);
+	if (!vpmem) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	vpmem->vdev = vdev;
+	err = init_vq(vpmem);
+	if (err)
+		goto out_err;
+
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			start, &vpmem->start);
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			size, &vpmem->size);
+
+	res.start = vpmem->start;
+	res.end   = vpmem->start + vpmem->size-1;
+	vpmem->nd_desc.provider_name = "virtio-pmem";
+	vpmem->nd_desc.module = THIS_MODULE;
+
+	vpmem->nvdimm_bus = nvdimm_bus = nvdimm_bus_register(&vdev->dev,
+						&vpmem->nd_desc);
+	if (!nvdimm_bus)
+		goto out_vq;
+
+	dev_set_drvdata(&vdev->dev, nvdimm_bus);
+	memset(&ndr_desc, 0, sizeof(ndr_desc));
+
+	ndr_desc.res = &res;
+	ndr_desc.numa_node = nid;
+	ndr_desc.flush = virtio_pmem_flush;
+	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
+	nd_region->provider_data =  dev_to_virtio
+					(nd_region->dev.parent->parent);
+
+	if (!nd_region)
+		goto out_nd;
+
+	//virtio_device_ready(vdev);
+	return 0;
+out_nd:
+	err = -ENXIO;
+	nvdimm_bus_unregister(nvdimm_bus);
+out_vq:
+	vdev->config->del_vqs(vdev);
+out_err:
+	dev_err(&vdev->dev, "failed to register virtio pmem memory\n");
+	return err;
+}
+
+static void virtio_pmem_remove(struct virtio_device *vdev)
+{
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
+
+	nvdimm_bus_unregister(nvdimm_bus);
+	vdev->config->del_vqs(vdev);
+	kfree(vpmem);
+}
+
+static struct virtio_driver virtio_pmem_driver = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.probe			= virtio_pmem_probe,
+	.remove			= virtio_pmem_remove,
+};
+
+module_virtio_driver(virtio_pmem_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio pmem driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_pmem.h b/include/linux/virtio_pmem.h
new file mode 100644
index 0000000..224f9d9
--- /dev/null
+++ b/include/linux/virtio_pmem.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * virtio_pmem.h: virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ **/
+
+#ifndef _LINUX_VIRTIO_PMEM_H
+#define _LINUX_VIRTIO_PMEM_H
+
+#include <linux/virtio_ids.h>
+#include <linux/module.h>
+#include <linux/virtio_config.h>
+#include <uapi/linux/virtio_pmem.h>
+#include <linux/libnvdimm.h>
+#include <linux/spinlock.h>
+
+struct virtio_pmem_request {
+	/* Host return status corresponding to flush request */
+	int ret;
+
+	/* command name*/
+	char name[16];
+
+	/* Wait queue to process deferred work after ack from host */
+	wait_queue_head_t host_acked;
+	bool done;
+
+	/* Wait queue to process deferred work after virt queue buffer avail */
+	wait_queue_head_t wq_buf;
+	bool wq_buf_avail;
+	struct list_head list;
+};
+
+struct virtio_pmem {
+	struct virtio_device *vdev;
+
+	/* Virtio pmem request queue */
+	struct virtqueue *req_vq;
+
+	/* nvdimm bus registers virtio pmem device */
+	struct nvdimm_bus *nvdimm_bus;
+	struct nvdimm_bus_descriptor nd_desc;
+
+	/* List to store deferred work if virtqueue is full */
+	struct list_head req_list;
+
+	/* Synchronize virtqueue data */
+	spinlock_t pmem_lock;
+
+	/* Memory region information */
+	uint64_t start;
+	uint64_t size;
+};
+
+void host_ack(struct virtqueue *vq);
+int virtio_pmem_flush(struct nd_region *nd_region);
+#endif
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 6d5c3b2..3463895 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -43,5 +43,6 @@
 #define VIRTIO_ID_INPUT        18 /* virtio input */
 #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
 #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
+#define VIRTIO_ID_PMEM         25 /* virtio pmem */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/uapi/linux/virtio_pmem.h b/include/uapi/linux/virtio_pmem.h
new file mode 100644
index 0000000..fa3f7d5
--- /dev/null
+++ b/include/uapi/linux/virtio_pmem.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _UAPI_LINUX_VIRTIO_PMEM_H
+#define _UAPI_LINUX_VIRTIO_PMEM_H
+
+struct virtio_pmem_config {
+	__le64 start;
+	__le64 size;
+};
+#endif
-- 
2.9.3

[PATCH v3 2/5] virtio-pmem: Add virtio pmem driver

[Pankaj Gupta]

This patch adds virtio-pmem driver for KVM guest.

Guest reads the persistent memory range information from
Qemu over VIRTIO and registers it on nvdimm_bus. It also
creates a nd_region object with the persistent memory
range information so that existing 'nvdimm/pmem' driver
can reserve this into system memory map. This way
'virtio-pmem' driver uses existing functionality of pmem
driver to register persistent memory compatible for DAX
capable filesystems.

This also provides function to perform guest flush over
VIRTIO from 'pmem' driver when userspace performs flush
on DAX memory range.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/nvdimm/virtio_pmem.c     |  84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |  10 ++++
 drivers/virtio/Makefile          |   1 +
 drivers/virtio/pmem.c            | 124 +++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_pmem.h      |  60 +++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |   1 +
 include/uapi/linux/virtio_pmem.h |  10 ++++
 7 files changed, 290 insertions(+)
 create mode 100644 drivers/nvdimm/virtio_pmem.c
 create mode 100644 drivers/virtio/pmem.c
 create mode 100644 include/linux/virtio_pmem.h
 create mode 100644 include/uapi/linux/virtio_pmem.h

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
new file mode 100644
index 0000000..2a1b1ba
--- /dev/null
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ */
+#include <linux/virtio_pmem.h>
+#include "nd.h"
+
+ /* The interrupt handler */
+void host_ack(struct virtqueue *vq)
+{
+	unsigned int len;
+	unsigned long flags;
+	struct virtio_pmem_request *req, *req_buf;
+	struct virtio_pmem *vpmem = vq->vdev->priv;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+		req->done = true;
+		wake_up(&req->host_acked);
+
+		if (!list_empty(&vpmem->req_list)) {
+			req_buf = list_first_entry(&vpmem->req_list,
+					struct virtio_pmem_request, list);
+			list_del(&vpmem->req_list);
+			req_buf->wq_buf_avail = true;
+			wake_up(&req_buf->wq_buf);
+		}
+	}
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+}
+EXPORT_SYMBOL_GPL(host_ack);
+
+ /* The request submission function */
+int virtio_pmem_flush(struct nd_region *nd_region)
+{
+	int err;
+	unsigned long flags;
+	struct scatterlist *sgs[2], sg, ret;
+	struct virtio_device *vdev = nd_region->provider_data;
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct virtio_pmem_request *req;
+
+	might_sleep();
+	req = kmalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	req->done = req->wq_buf_avail = false;
+	strcpy(req->name, "FLUSH");
+	init_waitqueue_head(&req->host_acked);
+	init_waitqueue_head(&req->wq_buf);
+	sg_init_one(&sg, req->name, strlen(req->name));
+	sgs[0] = &sg;
+	sg_init_one(&ret, &req->ret, sizeof(req->ret));
+	sgs[1] = &ret;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
+	if (err) {
+		dev_err(&vdev->dev, "failed to send command to virtio pmem device\n");
+
+		list_add_tail(&vpmem->req_list, &req->list);
+		spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+		/* When host has read buffer, this completes via host_ack */
+		wait_event(req->wq_buf, req->wq_buf_avail);
+		spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	}
+	virtqueue_kick(vpmem->req_vq);
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+	/* When host has read buffer, this completes via host_ack */
+	wait_event(req->host_acked, req->done);
+	err = req->ret;
+	kfree(req);
+
+	return err;
+};
+EXPORT_SYMBOL_GPL(virtio_pmem_flush);
+MODULE_LICENSE("GPL");
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 3589764..9f634a2 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -42,6 +42,16 @@ config VIRTIO_PCI_LEGACY
 
 	  If unsure, say Y.
 
+config VIRTIO_PMEM
+	tristate "Support for virtio pmem driver"
+	depends on VIRTIO
+	depends on LIBNVDIMM
+	help
+	This driver provides support for virtio based flushing interface
+	for persistent memory range.
+
+	If unsure, say M.
+
 config VIRTIO_BALLOON
 	tristate "Virtio balloon driver"
 	depends on VIRTIO
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 3a2b5c5..143ce91 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VIRTIO_PMEM) += pmem.o ../nvdimm/virtio_pmem.o
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
new file mode 100644
index 0000000..51f5349
--- /dev/null
+++ b/drivers/virtio/pmem.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and registers the virtual pmem device
+ * with libnvdimm core.
+ */
+#include <linux/virtio_pmem.h>
+#include <../../drivers/nvdimm/nd.h>
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+ /* Initialize virt queue */
+static int init_vq(struct virtio_pmem *vpmem)
+{
+	struct virtqueue *vq;
+
+	/* single vq */
+	vpmem->req_vq = vq = virtio_find_single_vq(vpmem->vdev,
+				host_ack, "flush_queue");
+	if (IS_ERR(vq))
+		return PTR_ERR(vq);
+
+	spin_lock_init(&vpmem->pmem_lock);
+	INIT_LIST_HEAD(&vpmem->req_list);
+
+	return 0;
+};
+
+static int virtio_pmem_probe(struct virtio_device *vdev)
+{
+	int err = 0;
+	struct resource res;
+	struct virtio_pmem *vpmem;
+	struct nvdimm_bus *nvdimm_bus;
+	struct nd_region_desc ndr_desc;
+	int nid = dev_to_node(&vdev->dev);
+	struct nd_region *nd_region;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem),
+			GFP_KERNEL);
+	if (!vpmem) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	vpmem->vdev = vdev;
+	err = init_vq(vpmem);
+	if (err)
+		goto out_err;
+
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			start, &vpmem->start);
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			size, &vpmem->size);
+
+	res.start = vpmem->start;
+	res.end   = vpmem->start + vpmem->size-1;
+	vpmem->nd_desc.provider_name = "virtio-pmem";
+	vpmem->nd_desc.module = THIS_MODULE;
+
+	vpmem->nvdimm_bus = nvdimm_bus = nvdimm_bus_register(&vdev->dev,
+						&vpmem->nd_desc);
+	if (!nvdimm_bus)
+		goto out_vq;
+
+	dev_set_drvdata(&vdev->dev, nvdimm_bus);
+	memset(&ndr_desc, 0, sizeof(ndr_desc));
+
+	ndr_desc.res = &res;
+	ndr_desc.numa_node = nid;
+	ndr_desc.flush = virtio_pmem_flush;
+	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
+	nd_region->provider_data =  dev_to_virtio
+					(nd_region->dev.parent->parent);
+
+	if (!nd_region)
+		goto out_nd;
+
+	//virtio_device_ready(vdev);
+	return 0;
+out_nd:
+	err = -ENXIO;
+	nvdimm_bus_unregister(nvdimm_bus);
+out_vq:
+	vdev->config->del_vqs(vdev);
+out_err:
+	dev_err(&vdev->dev, "failed to register virtio pmem memory\n");
+	return err;
+}
+
+static void virtio_pmem_remove(struct virtio_device *vdev)
+{
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
+
+	nvdimm_bus_unregister(nvdimm_bus);
+	vdev->config->del_vqs(vdev);
+	kfree(vpmem);
+}
+
+static struct virtio_driver virtio_pmem_driver = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.probe			= virtio_pmem_probe,
+	.remove			= virtio_pmem_remove,
+};
+
+module_virtio_driver(virtio_pmem_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio pmem driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_pmem.h b/include/linux/virtio_pmem.h
new file mode 100644
index 0000000..224f9d9
--- /dev/null
+++ b/include/linux/virtio_pmem.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * virtio_pmem.h: virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ **/
+
+#ifndef _LINUX_VIRTIO_PMEM_H
+#define _LINUX_VIRTIO_PMEM_H
+
+#include <linux/virtio_ids.h>
+#include <linux/module.h>
+#include <linux/virtio_config.h>
+#include <uapi/linux/virtio_pmem.h>
+#include <linux/libnvdimm.h>
+#include <linux/spinlock.h>
+
+struct virtio_pmem_request {
+	/* Host return status corresponding to flush request */
+	int ret;
+
+	/* command name*/
+	char name[16];
+
+	/* Wait queue to process deferred work after ack from host */
+	wait_queue_head_t host_acked;
+	bool done;
+
+	/* Wait queue to process deferred work after virt queue buffer avail */
+	wait_queue_head_t wq_buf;
+	bool wq_buf_avail;
+	struct list_head list;
+};
+
+struct virtio_pmem {
+	struct virtio_device *vdev;
+
+	/* Virtio pmem request queue */
+	struct virtqueue *req_vq;
+
+	/* nvdimm bus registers virtio pmem device */
+	struct nvdimm_bus *nvdimm_bus;
+	struct nvdimm_bus_descriptor nd_desc;
+
+	/* List to store deferred work if virtqueue is full */
+	struct list_head req_list;
+
+	/* Synchronize virtqueue data */
+	spinlock_t pmem_lock;
+
+	/* Memory region information */
+	uint64_t start;
+	uint64_t size;
+};
+
+void host_ack(struct virtqueue *vq);
+int virtio_pmem_flush(struct nd_region *nd_region);
+#endif
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 6d5c3b2..3463895 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -43,5 +43,6 @@
 #define VIRTIO_ID_INPUT        18 /* virtio input */
 #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
 #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
+#define VIRTIO_ID_PMEM         25 /* virtio pmem */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/uapi/linux/virtio_pmem.h b/include/uapi/linux/virtio_pmem.h
new file mode 100644
index 0000000..fa3f7d5
--- /dev/null
+++ b/include/uapi/linux/virtio_pmem.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _UAPI_LINUX_VIRTIO_PMEM_H
+#define _UAPI_LINUX_VIRTIO_PMEM_H
+
+struct virtio_pmem_config {
+	__le64 start;
+	__le64 size;
+};
+#endif
-- 
2.9.3

[Qemu-devel] [PATCH v3 2/5] virtio-pmem: Add virtio pmem driver

[Pankaj Gupta]

This patch adds virtio-pmem driver for KVM guest.

Guest reads the persistent memory range information from
Qemu over VIRTIO and registers it on nvdimm_bus. It also
creates a nd_region object with the persistent memory
range information so that existing 'nvdimm/pmem' driver
can reserve this into system memory map. This way
'virtio-pmem' driver uses existing functionality of pmem
driver to register persistent memory compatible for DAX
capable filesystems.

This also provides function to perform guest flush over
VIRTIO from 'pmem' driver when userspace performs flush
on DAX memory range.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/nvdimm/virtio_pmem.c     |  84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |  10 ++++
 drivers/virtio/Makefile          |   1 +
 drivers/virtio/pmem.c            | 124 +++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_pmem.h      |  60 +++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |   1 +
 include/uapi/linux/virtio_pmem.h |  10 ++++
 7 files changed, 290 insertions(+)
 create mode 100644 drivers/nvdimm/virtio_pmem.c
 create mode 100644 drivers/virtio/pmem.c
 create mode 100644 include/linux/virtio_pmem.h
 create mode 100644 include/uapi/linux/virtio_pmem.h

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
new file mode 100644
index 0000000..2a1b1ba
--- /dev/null
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ */
+#include <linux/virtio_pmem.h>
+#include "nd.h"
+
+ /* The interrupt handler */
+void host_ack(struct virtqueue *vq)
+{
+	unsigned int len;
+	unsigned long flags;
+	struct virtio_pmem_request *req, *req_buf;
+	struct virtio_pmem *vpmem = vq->vdev->priv;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+		req->done = true;
+		wake_up(&req->host_acked);
+
+		if (!list_empty(&vpmem->req_list)) {
+			req_buf = list_first_entry(&vpmem->req_list,
+					struct virtio_pmem_request, list);
+			list_del(&vpmem->req_list);
+			req_buf->wq_buf_avail = true;
+			wake_up(&req_buf->wq_buf);
+		}
+	}
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+}
+EXPORT_SYMBOL_GPL(host_ack);
+
+ /* The request submission function */
+int virtio_pmem_flush(struct nd_region *nd_region)
+{
+	int err;
+	unsigned long flags;
+	struct scatterlist *sgs[2], sg, ret;
+	struct virtio_device *vdev = nd_region->provider_data;
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct virtio_pmem_request *req;
+
+	might_sleep();
+	req = kmalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	req->done = req->wq_buf_avail = false;
+	strcpy(req->name, "FLUSH");
+	init_waitqueue_head(&req->host_acked);
+	init_waitqueue_head(&req->wq_buf);
+	sg_init_one(&sg, req->name, strlen(req->name));
+	sgs[0] = &sg;
+	sg_init_one(&ret, &req->ret, sizeof(req->ret));
+	sgs[1] = &ret;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
+	if (err) {
+		dev_err(&vdev->dev, "failed to send command to virtio pmem device\n");
+
+		list_add_tail(&vpmem->req_list, &req->list);
+		spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+		/* When host has read buffer, this completes via host_ack */
+		wait_event(req->wq_buf, req->wq_buf_avail);
+		spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	}
+	virtqueue_kick(vpmem->req_vq);
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+	/* When host has read buffer, this completes via host_ack */
+	wait_event(req->host_acked, req->done);
+	err = req->ret;
+	kfree(req);
+
+	return err;
+};
+EXPORT_SYMBOL_GPL(virtio_pmem_flush);
+MODULE_LICENSE("GPL");
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 3589764..9f634a2 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -42,6 +42,16 @@ config VIRTIO_PCI_LEGACY
 
 	  If unsure, say Y.
 
+config VIRTIO_PMEM
+	tristate "Support for virtio pmem driver"
+	depends on VIRTIO
+	depends on LIBNVDIMM
+	help
+	This driver provides support for virtio based flushing interface
+	for persistent memory range.
+
+	If unsure, say M.
+
 config VIRTIO_BALLOON
 	tristate "Virtio balloon driver"
 	depends on VIRTIO
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 3a2b5c5..143ce91 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VIRTIO_PMEM) += pmem.o ../nvdimm/virtio_pmem.o
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
new file mode 100644
index 0000000..51f5349
--- /dev/null
+++ b/drivers/virtio/pmem.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and registers the virtual pmem device
+ * with libnvdimm core.
+ */
+#include <linux/virtio_pmem.h>
+#include <../../drivers/nvdimm/nd.h>
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+ /* Initialize virt queue */
+static int init_vq(struct virtio_pmem *vpmem)
+{
+	struct virtqueue *vq;
+
+	/* single vq */
+	vpmem->req_vq = vq = virtio_find_single_vq(vpmem->vdev,
+				host_ack, "flush_queue");
+	if (IS_ERR(vq))
+		return PTR_ERR(vq);
+
+	spin_lock_init(&vpmem->pmem_lock);
+	INIT_LIST_HEAD(&vpmem->req_list);
+
+	return 0;
+};
+
+static int virtio_pmem_probe(struct virtio_device *vdev)
+{
+	int err = 0;
+	struct resource res;
+	struct virtio_pmem *vpmem;
+	struct nvdimm_bus *nvdimm_bus;
+	struct nd_region_desc ndr_desc;
+	int nid = dev_to_node(&vdev->dev);
+	struct nd_region *nd_region;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem),
+			GFP_KERNEL);
+	if (!vpmem) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	vpmem->vdev = vdev;
+	err = init_vq(vpmem);
+	if (err)
+		goto out_err;
+
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			start, &vpmem->start);
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			size, &vpmem->size);
+
+	res.start = vpmem->start;
+	res.end   = vpmem->start + vpmem->size-1;
+	vpmem->nd_desc.provider_name = "virtio-pmem";
+	vpmem->nd_desc.module = THIS_MODULE;
+
+	vpmem->nvdimm_bus = nvdimm_bus = nvdimm_bus_register(&vdev->dev,
+						&vpmem->nd_desc);
+	if (!nvdimm_bus)
+		goto out_vq;
+
+	dev_set_drvdata(&vdev->dev, nvdimm_bus);
+	memset(&ndr_desc, 0, sizeof(ndr_desc));
+
+	ndr_desc.res = &res;
+	ndr_desc.numa_node = nid;
+	ndr_desc.flush = virtio_pmem_flush;
+	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
+	nd_region->provider_data =  dev_to_virtio
+					(nd_region->dev.parent->parent);
+
+	if (!nd_region)
+		goto out_nd;
+
+	//virtio_device_ready(vdev);
+	return 0;
+out_nd:
+	err = -ENXIO;
+	nvdimm_bus_unregister(nvdimm_bus);
+out_vq:
+	vdev->config->del_vqs(vdev);
+out_err:
+	dev_err(&vdev->dev, "failed to register virtio pmem memory\n");
+	return err;
+}
+
+static void virtio_pmem_remove(struct virtio_device *vdev)
+{
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
+
+	nvdimm_bus_unregister(nvdimm_bus);
+	vdev->config->del_vqs(vdev);
+	kfree(vpmem);
+}
+
+static struct virtio_driver virtio_pmem_driver = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.probe			= virtio_pmem_probe,
+	.remove			= virtio_pmem_remove,
+};
+
+module_virtio_driver(virtio_pmem_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio pmem driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_pmem.h b/include/linux/virtio_pmem.h
new file mode 100644
index 0000000..224f9d9
--- /dev/null
+++ b/include/linux/virtio_pmem.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * virtio_pmem.h: virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ **/
+
+#ifndef _LINUX_VIRTIO_PMEM_H
+#define _LINUX_VIRTIO_PMEM_H
+
+#include <linux/virtio_ids.h>
+#include <linux/module.h>
+#include <linux/virtio_config.h>
+#include <uapi/linux/virtio_pmem.h>
+#include <linux/libnvdimm.h>
+#include <linux/spinlock.h>
+
+struct virtio_pmem_request {
+	/* Host return status corresponding to flush request */
+	int ret;
+
+	/* command name*/
+	char name[16];
+
+	/* Wait queue to process deferred work after ack from host */
+	wait_queue_head_t host_acked;
+	bool done;
+
+	/* Wait queue to process deferred work after virt queue buffer avail */
+	wait_queue_head_t wq_buf;
+	bool wq_buf_avail;
+	struct list_head list;
+};
+
+struct virtio_pmem {
+	struct virtio_device *vdev;
+
+	/* Virtio pmem request queue */
+	struct virtqueue *req_vq;
+
+	/* nvdimm bus registers virtio pmem device */
+	struct nvdimm_bus *nvdimm_bus;
+	struct nvdimm_bus_descriptor nd_desc;
+
+	/* List to store deferred work if virtqueue is full */
+	struct list_head req_list;
+
+	/* Synchronize virtqueue data */
+	spinlock_t pmem_lock;
+
+	/* Memory region information */
+	uint64_t start;
+	uint64_t size;
+};
+
+void host_ack(struct virtqueue *vq);
+int virtio_pmem_flush(struct nd_region *nd_region);
+#endif
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 6d5c3b2..3463895 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -43,5 +43,6 @@
 #define VIRTIO_ID_INPUT        18 /* virtio input */
 #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
 #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
+#define VIRTIO_ID_PMEM         25 /* virtio pmem */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/uapi/linux/virtio_pmem.h b/include/uapi/linux/virtio_pmem.h
new file mode 100644
index 0000000..fa3f7d5
--- /dev/null
+++ b/include/uapi/linux/virtio_pmem.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _UAPI_LINUX_VIRTIO_PMEM_H
+#define _UAPI_LINUX_VIRTIO_PMEM_H
+
+struct virtio_pmem_config {
+	__le64 start;
+	__le64 size;
+};
+#endif
-- 
2.9.3

[PATCH v3 2/5] virtio-pmem: Add virtio pmem driver

[Pankaj Gupta]

This patch adds virtio-pmem driver for KVM guest.

Guest reads the persistent memory range information from
Qemu over VIRTIO and registers it on nvdimm_bus. It also
creates a nd_region object with the persistent memory
range information so that existing 'nvdimm/pmem' driver
can reserve this into system memory map. This way
'virtio-pmem' driver uses existing functionality of pmem
driver to register persistent memory compatible for DAX
capable filesystems.

This also provides function to perform guest flush over
VIRTIO from 'pmem' driver when userspace performs flush
on DAX memory range.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/nvdimm/virtio_pmem.c     |  84 ++++++++++++++++++++++++++
 drivers/virtio/Kconfig           |  10 ++++
 drivers/virtio/Makefile          |   1 +
 drivers/virtio/pmem.c            | 124 +++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_pmem.h      |  60 +++++++++++++++++++
 include/uapi/linux/virtio_ids.h  |   1 +
 include/uapi/linux/virtio_pmem.h |  10 ++++
 7 files changed, 290 insertions(+)
 create mode 100644 drivers/nvdimm/virtio_pmem.c
 create mode 100644 drivers/virtio/pmem.c
 create mode 100644 include/linux/virtio_pmem.h
 create mode 100644 include/uapi/linux/virtio_pmem.h

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
new file mode 100644
index 0000000..2a1b1ba
--- /dev/null
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ */
+#include <linux/virtio_pmem.h>
+#include "nd.h"
+
+ /* The interrupt handler */
+void host_ack(struct virtqueue *vq)
+{
+	unsigned int len;
+	unsigned long flags;
+	struct virtio_pmem_request *req, *req_buf;
+	struct virtio_pmem *vpmem = vq->vdev->priv;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+		req->done = true;
+		wake_up(&req->host_acked);
+
+		if (!list_empty(&vpmem->req_list)) {
+			req_buf = list_first_entry(&vpmem->req_list,
+					struct virtio_pmem_request, list);
+			list_del(&vpmem->req_list);
+			req_buf->wq_buf_avail = true;
+			wake_up(&req_buf->wq_buf);
+		}
+	}
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+}
+EXPORT_SYMBOL_GPL(host_ack);
+
+ /* The request submission function */
+int virtio_pmem_flush(struct nd_region *nd_region)
+{
+	int err;
+	unsigned long flags;
+	struct scatterlist *sgs[2], sg, ret;
+	struct virtio_device *vdev = nd_region->provider_data;
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct virtio_pmem_request *req;
+
+	might_sleep();
+	req = kmalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	req->done = req->wq_buf_avail = false;
+	strcpy(req->name, "FLUSH");
+	init_waitqueue_head(&req->host_acked);
+	init_waitqueue_head(&req->wq_buf);
+	sg_init_one(&sg, req->name, strlen(req->name));
+	sgs[0] = &sg;
+	sg_init_one(&ret, &req->ret, sizeof(req->ret));
+	sgs[1] = &ret;
+
+	spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
+	if (err) {
+		dev_err(&vdev->dev, "failed to send command to virtio pmem device\n");
+
+		list_add_tail(&vpmem->req_list, &req->list);
+		spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+		/* When host has read buffer, this completes via host_ack */
+		wait_event(req->wq_buf, req->wq_buf_avail);
+		spin_lock_irqsave(&vpmem->pmem_lock, flags);
+	}
+	virtqueue_kick(vpmem->req_vq);
+	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
+
+	/* When host has read buffer, this completes via host_ack */
+	wait_event(req->host_acked, req->done);
+	err = req->ret;
+	kfree(req);
+
+	return err;
+};
+EXPORT_SYMBOL_GPL(virtio_pmem_flush);
+MODULE_LICENSE("GPL");
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 3589764..9f634a2 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -42,6 +42,16 @@ config VIRTIO_PCI_LEGACY
 
 	  If unsure, say Y.
 
+config VIRTIO_PMEM
+	tristate "Support for virtio pmem driver"
+	depends on VIRTIO
+	depends on LIBNVDIMM
+	help
+	This driver provides support for virtio based flushing interface
+	for persistent memory range.
+
+	If unsure, say M.
+
 config VIRTIO_BALLOON
 	tristate "Virtio balloon driver"
 	depends on VIRTIO
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 3a2b5c5..143ce91 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VIRTIO_PMEM) += pmem.o ../nvdimm/virtio_pmem.o
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
new file mode 100644
index 0000000..51f5349
--- /dev/null
+++ b/drivers/virtio/pmem.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio_pmem.c: Virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and registers the virtual pmem device
+ * with libnvdimm core.
+ */
+#include <linux/virtio_pmem.h>
+#include <../../drivers/nvdimm/nd.h>
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+ /* Initialize virt queue */
+static int init_vq(struct virtio_pmem *vpmem)
+{
+	struct virtqueue *vq;
+
+	/* single vq */
+	vpmem->req_vq = vq = virtio_find_single_vq(vpmem->vdev,
+				host_ack, "flush_queue");
+	if (IS_ERR(vq))
+		return PTR_ERR(vq);
+
+	spin_lock_init(&vpmem->pmem_lock);
+	INIT_LIST_HEAD(&vpmem->req_list);
+
+	return 0;
+};
+
+static int virtio_pmem_probe(struct virtio_device *vdev)
+{
+	int err = 0;
+	struct resource res;
+	struct virtio_pmem *vpmem;
+	struct nvdimm_bus *nvdimm_bus;
+	struct nd_region_desc ndr_desc;
+	int nid = dev_to_node(&vdev->dev);
+	struct nd_region *nd_region;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem),
+			GFP_KERNEL);
+	if (!vpmem) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	vpmem->vdev = vdev;
+	err = init_vq(vpmem);
+	if (err)
+		goto out_err;
+
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			start, &vpmem->start);
+	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
+			size, &vpmem->size);
+
+	res.start = vpmem->start;
+	res.end   = vpmem->start + vpmem->size-1;
+	vpmem->nd_desc.provider_name = "virtio-pmem";
+	vpmem->nd_desc.module = THIS_MODULE;
+
+	vpmem->nvdimm_bus = nvdimm_bus = nvdimm_bus_register(&vdev->dev,
+						&vpmem->nd_desc);
+	if (!nvdimm_bus)
+		goto out_vq;
+
+	dev_set_drvdata(&vdev->dev, nvdimm_bus);
+	memset(&ndr_desc, 0, sizeof(ndr_desc));
+
+	ndr_desc.res = &res;
+	ndr_desc.numa_node = nid;
+	ndr_desc.flush = virtio_pmem_flush;
+	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
+	nd_region->provider_data =  dev_to_virtio
+					(nd_region->dev.parent->parent);
+
+	if (!nd_region)
+		goto out_nd;
+
+	//virtio_device_ready(vdev);
+	return 0;
+out_nd:
+	err = -ENXIO;
+	nvdimm_bus_unregister(nvdimm_bus);
+out_vq:
+	vdev->config->del_vqs(vdev);
+out_err:
+	dev_err(&vdev->dev, "failed to register virtio pmem memory\n");
+	return err;
+}
+
+static void virtio_pmem_remove(struct virtio_device *vdev)
+{
+	struct virtio_pmem *vpmem = vdev->priv;
+	struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
+
+	nvdimm_bus_unregister(nvdimm_bus);
+	vdev->config->del_vqs(vdev);
+	kfree(vpmem);
+}
+
+static struct virtio_driver virtio_pmem_driver = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.probe			= virtio_pmem_probe,
+	.remove			= virtio_pmem_remove,
+};
+
+module_virtio_driver(virtio_pmem_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio pmem driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_pmem.h b/include/linux/virtio_pmem.h
new file mode 100644
index 0000000..224f9d9
--- /dev/null
+++ b/include/linux/virtio_pmem.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * virtio_pmem.h: virtio pmem Driver
+ *
+ * Discovers persistent memory range information
+ * from host and provides a virtio based flushing
+ * interface.
+ **/
+
+#ifndef _LINUX_VIRTIO_PMEM_H
+#define _LINUX_VIRTIO_PMEM_H
+
+#include <linux/virtio_ids.h>
+#include <linux/module.h>
+#include <linux/virtio_config.h>
+#include <uapi/linux/virtio_pmem.h>
+#include <linux/libnvdimm.h>
+#include <linux/spinlock.h>
+
+struct virtio_pmem_request {
+	/* Host return status corresponding to flush request */
+	int ret;
+
+	/* command name*/
+	char name[16];
+
+	/* Wait queue to process deferred work after ack from host */
+	wait_queue_head_t host_acked;
+	bool done;
+
+	/* Wait queue to process deferred work after virt queue buffer avail */
+	wait_queue_head_t wq_buf;
+	bool wq_buf_avail;
+	struct list_head list;
+};
+
+struct virtio_pmem {
+	struct virtio_device *vdev;
+
+	/* Virtio pmem request queue */
+	struct virtqueue *req_vq;
+
+	/* nvdimm bus registers virtio pmem device */
+	struct nvdimm_bus *nvdimm_bus;
+	struct nvdimm_bus_descriptor nd_desc;
+
+	/* List to store deferred work if virtqueue is full */
+	struct list_head req_list;
+
+	/* Synchronize virtqueue data */
+	spinlock_t pmem_lock;
+
+	/* Memory region information */
+	uint64_t start;
+	uint64_t size;
+};
+
+void host_ack(struct virtqueue *vq);
+int virtio_pmem_flush(struct nd_region *nd_region);
+#endif
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 6d5c3b2..3463895 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -43,5 +43,6 @@
 #define VIRTIO_ID_INPUT        18 /* virtio input */
 #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
 #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
+#define VIRTIO_ID_PMEM         25 /* virtio pmem */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/uapi/linux/virtio_pmem.h b/include/uapi/linux/virtio_pmem.h
new file mode 100644
index 0000000..fa3f7d5
--- /dev/null
+++ b/include/uapi/linux/virtio_pmem.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _UAPI_LINUX_VIRTIO_PMEM_H
+#define _UAPI_LINUX_VIRTIO_PMEM_H
+
+struct virtio_pmem_config {
+	__le64 start;
+	__le64 size;
+};
+#endif
-- 
2.9.3

[PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

This patch adds 'DAXDEV_BUFFERED' flag which is set
for virtio pmem corresponding nd_region. This later
is used to disable MAP_SYNC functionality for ext4
& xfs filesystem.

Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 drivers/dax/super.c          | 17 +++++++++++++++++
 drivers/nvdimm/pmem.c        |  3 +++
 drivers/nvdimm/region_devs.c |  7 +++++++
 drivers/virtio/pmem.c        |  1 +
 include/linux/dax.h          |  9 +++++++++
 include/linux/libnvdimm.h    |  6 ++++++
 6 files changed, 43 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 6e928f3..9128740 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -167,6 +167,8 @@ enum dax_device_flags {
 	DAXDEV_ALIVE,
 	/* gate whether dax_flush() calls the low level flush routine */
 	DAXDEV_WRITE_CACHE,
+	/* flag to disable MAP_SYNC for virtio based host page cache flush */
+	DAXDEV_BUFFERED,
 };
 
 /**
@@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+	if (wc)
+		set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+	else
+		clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
+
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
 	lockdep_assert_held(&dax_srcu);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index fe1217b..8d190a3 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -472,6 +472,9 @@ static int pmem_attach_disk(struct device *dev,
 		return -ENOMEM;
 	}
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
+
+	/* Set buffered bit in 'dax_dev' for virtio pmem */
+	virtio_pmem_host_cache(dax_dev, nvdimm_is_buffered(nd_region));
 	pmem->dax_dev = dax_dev;
 
 	gendev = disk_to_dev(disk);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index f8218b4..1f8b2be 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1264,6 +1264,13 @@ int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
 	return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
 }
 
+int nvdimm_is_buffered(struct nd_region *nd_region)
+{
+	return is_nd_pmem(&nd_region->dev) &&
+		test_bit(ND_REGION_BUFFERED, &nd_region->flags);
+}
+EXPORT_SYMBOL_GPL(nvdimm_is_buffered);
+
 void __exit nd_region_devs_exit(void)
 {
 	ida_destroy(&region_ida);
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
index 51f5349..901767b 100644
--- a/drivers/virtio/pmem.c
+++ b/drivers/virtio/pmem.c
@@ -81,6 +81,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	ndr_desc.numa_node = nid;
 	ndr_desc.flush = virtio_pmem_flush;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	set_bit(ND_REGION_BUFFERED, &ndr_desc.flags);
 	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
 	nd_region->provider_data =  dev_to_virtio
 					(nd_region->dev.parent->parent);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0dd316a..d16e03e 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -37,6 +37,8 @@ void put_dax(struct dax_device *dax_dev);
 void kill_dax(struct dax_device *dax_dev);
 void dax_write_cache(struct dax_device *dax_dev, bool wc);
 bool dax_write_cache_enabled(struct dax_device *dax_dev);
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc);
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev);
 #else
 static inline struct dax_device *dax_get_by_host(const char *host)
 {
@@ -64,6 +66,13 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
 {
 	return false;
 }
+static inline void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+}
+static inline bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return false;
+}
 #endif
 
 struct writeback_control;
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index ca8bc07..94616f1 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -64,6 +64,11 @@ enum {
 	 */
 	ND_REGION_PERSIST_MEMCTRL = 2,
 
+	/* provides virtio based asynchronous flush mechanism for buffered
+	 * host page cache.
+	 */
+	ND_REGION_BUFFERED = 3,
+
 	/* mark newly adjusted resources as requiring a label update */
 	DPA_RESOURCE_ADJUSTED = 1 << 0,
 };
@@ -265,6 +270,7 @@ int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 int nvdimm_in_overwrite(struct nvdimm *nvdimm);
+int nvdimm_is_buffered(struct nd_region *nd_region);
 
 static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 		unsigned int buf_len, int *cmd_rc)
-- 
2.9.3

[PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

This patch adds 'DAXDEV_BUFFERED' flag which is set
for virtio pmem corresponding nd_region. This later
is used to disable MAP_SYNC functionality for ext4
& xfs filesystem.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/dax/super.c          | 17 +++++++++++++++++
 drivers/nvdimm/pmem.c        |  3 +++
 drivers/nvdimm/region_devs.c |  7 +++++++
 drivers/virtio/pmem.c        |  1 +
 include/linux/dax.h          |  9 +++++++++
 include/linux/libnvdimm.h    |  6 ++++++
 6 files changed, 43 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 6e928f3..9128740 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -167,6 +167,8 @@ enum dax_device_flags {
 	DAXDEV_ALIVE,
 	/* gate whether dax_flush() calls the low level flush routine */
 	DAXDEV_WRITE_CACHE,
+	/* flag to disable MAP_SYNC for virtio based host page cache flush */
+	DAXDEV_BUFFERED,
 };
 
 /**
@@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+	if (wc)
+		set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+	else
+		clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
+
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
 	lockdep_assert_held(&dax_srcu);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index fe1217b..8d190a3 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -472,6 +472,9 @@ static int pmem_attach_disk(struct device *dev,
 		return -ENOMEM;
 	}
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
+
+	/* Set buffered bit in 'dax_dev' for virtio pmem */
+	virtio_pmem_host_cache(dax_dev, nvdimm_is_buffered(nd_region));
 	pmem->dax_dev = dax_dev;
 
 	gendev = disk_to_dev(disk);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index f8218b4..1f8b2be 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1264,6 +1264,13 @@ int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
 	return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
 }
 
+int nvdimm_is_buffered(struct nd_region *nd_region)
+{
+	return is_nd_pmem(&nd_region->dev) &&
+		test_bit(ND_REGION_BUFFERED, &nd_region->flags);
+}
+EXPORT_SYMBOL_GPL(nvdimm_is_buffered);
+
 void __exit nd_region_devs_exit(void)
 {
 	ida_destroy(&region_ida);
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
index 51f5349..901767b 100644
--- a/drivers/virtio/pmem.c
+++ b/drivers/virtio/pmem.c
@@ -81,6 +81,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	ndr_desc.numa_node = nid;
 	ndr_desc.flush = virtio_pmem_flush;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	set_bit(ND_REGION_BUFFERED, &ndr_desc.flags);
 	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
 	nd_region->provider_data =  dev_to_virtio
 					(nd_region->dev.parent->parent);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0dd316a..d16e03e 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -37,6 +37,8 @@ void put_dax(struct dax_device *dax_dev);
 void kill_dax(struct dax_device *dax_dev);
 void dax_write_cache(struct dax_device *dax_dev, bool wc);
 bool dax_write_cache_enabled(struct dax_device *dax_dev);
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc);
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev);
 #else
 static inline struct dax_device *dax_get_by_host(const char *host)
 {
@@ -64,6 +66,13 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
 {
 	return false;
 }
+static inline void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+}
+static inline bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return false;
+}
 #endif
 
 struct writeback_control;
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index ca8bc07..94616f1 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -64,6 +64,11 @@ enum {
 	 */
 	ND_REGION_PERSIST_MEMCTRL = 2,
 
+	/* provides virtio based asynchronous flush mechanism for buffered
+	 * host page cache.
+	 */
+	ND_REGION_BUFFERED = 3,
+
 	/* mark newly adjusted resources as requiring a label update */
 	DPA_RESOURCE_ADJUSTED = 1 << 0,
 };
@@ -265,6 +270,7 @@ int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 int nvdimm_in_overwrite(struct nvdimm *nvdimm);
+int nvdimm_is_buffered(struct nd_region *nd_region);
 
 static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 		unsigned int buf_len, int *cmd_rc)
-- 
2.9.3

[Qemu-devel] [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

This patch adds 'DAXDEV_BUFFERED' flag which is set
for virtio pmem corresponding nd_region. This later
is used to disable MAP_SYNC functionality for ext4
& xfs filesystem.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/dax/super.c          | 17 +++++++++++++++++
 drivers/nvdimm/pmem.c        |  3 +++
 drivers/nvdimm/region_devs.c |  7 +++++++
 drivers/virtio/pmem.c        |  1 +
 include/linux/dax.h          |  9 +++++++++
 include/linux/libnvdimm.h    |  6 ++++++
 6 files changed, 43 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 6e928f3..9128740 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -167,6 +167,8 @@ enum dax_device_flags {
 	DAXDEV_ALIVE,
 	/* gate whether dax_flush() calls the low level flush routine */
 	DAXDEV_WRITE_CACHE,
+	/* flag to disable MAP_SYNC for virtio based host page cache flush */
+	DAXDEV_BUFFERED,
 };
 
 /**
@@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+	if (wc)
+		set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+	else
+		clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
+
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
 	lockdep_assert_held(&dax_srcu);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index fe1217b..8d190a3 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -472,6 +472,9 @@ static int pmem_attach_disk(struct device *dev,
 		return -ENOMEM;
 	}
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
+
+	/* Set buffered bit in 'dax_dev' for virtio pmem */
+	virtio_pmem_host_cache(dax_dev, nvdimm_is_buffered(nd_region));
 	pmem->dax_dev = dax_dev;
 
 	gendev = disk_to_dev(disk);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index f8218b4..1f8b2be 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1264,6 +1264,13 @@ int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
 	return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
 }
 
+int nvdimm_is_buffered(struct nd_region *nd_region)
+{
+	return is_nd_pmem(&nd_region->dev) &&
+		test_bit(ND_REGION_BUFFERED, &nd_region->flags);
+}
+EXPORT_SYMBOL_GPL(nvdimm_is_buffered);
+
 void __exit nd_region_devs_exit(void)
 {
 	ida_destroy(&region_ida);
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
index 51f5349..901767b 100644
--- a/drivers/virtio/pmem.c
+++ b/drivers/virtio/pmem.c
@@ -81,6 +81,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	ndr_desc.numa_node = nid;
 	ndr_desc.flush = virtio_pmem_flush;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	set_bit(ND_REGION_BUFFERED, &ndr_desc.flags);
 	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
 	nd_region->provider_data =  dev_to_virtio
 					(nd_region->dev.parent->parent);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0dd316a..d16e03e 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -37,6 +37,8 @@ void put_dax(struct dax_device *dax_dev);
 void kill_dax(struct dax_device *dax_dev);
 void dax_write_cache(struct dax_device *dax_dev, bool wc);
 bool dax_write_cache_enabled(struct dax_device *dax_dev);
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc);
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev);
 #else
 static inline struct dax_device *dax_get_by_host(const char *host)
 {
@@ -64,6 +66,13 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
 {
 	return false;
 }
+static inline void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+}
+static inline bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return false;
+}
 #endif
 
 struct writeback_control;
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index ca8bc07..94616f1 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -64,6 +64,11 @@ enum {
 	 */
 	ND_REGION_PERSIST_MEMCTRL = 2,
 
+	/* provides virtio based asynchronous flush mechanism for buffered
+	 * host page cache.
+	 */
+	ND_REGION_BUFFERED = 3,
+
 	/* mark newly adjusted resources as requiring a label update */
 	DPA_RESOURCE_ADJUSTED = 1 << 0,
 };
@@ -265,6 +270,7 @@ int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 int nvdimm_in_overwrite(struct nvdimm *nvdimm);
+int nvdimm_is_buffered(struct nd_region *nd_region);
 
 static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 		unsigned int buf_len, int *cmd_rc)
-- 
2.9.3

[PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

This patch adds 'DAXDEV_BUFFERED' flag which is set
for virtio pmem corresponding nd_region. This later
is used to disable MAP_SYNC functionality for ext4
& xfs filesystem.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/dax/super.c          | 17 +++++++++++++++++
 drivers/nvdimm/pmem.c        |  3 +++
 drivers/nvdimm/region_devs.c |  7 +++++++
 drivers/virtio/pmem.c        |  1 +
 include/linux/dax.h          |  9 +++++++++
 include/linux/libnvdimm.h    |  6 ++++++
 6 files changed, 43 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 6e928f3..9128740 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -167,6 +167,8 @@ enum dax_device_flags {
 	DAXDEV_ALIVE,
 	/* gate whether dax_flush() calls the low level flush routine */
 	DAXDEV_WRITE_CACHE,
+	/* flag to disable MAP_SYNC for virtio based host page cache flush */
+	DAXDEV_BUFFERED,
 };
 
 /**
@@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+	if (wc)
+		set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+	else
+		clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
+
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
 	lockdep_assert_held(&dax_srcu);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index fe1217b..8d190a3 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -472,6 +472,9 @@ static int pmem_attach_disk(struct device *dev,
 		return -ENOMEM;
 	}
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
+
+	/* Set buffered bit in 'dax_dev' for virtio pmem */
+	virtio_pmem_host_cache(dax_dev, nvdimm_is_buffered(nd_region));
 	pmem->dax_dev = dax_dev;
 
 	gendev = disk_to_dev(disk);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index f8218b4..1f8b2be 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1264,6 +1264,13 @@ int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
 	return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
 }
 
+int nvdimm_is_buffered(struct nd_region *nd_region)
+{
+	return is_nd_pmem(&nd_region->dev) &&
+		test_bit(ND_REGION_BUFFERED, &nd_region->flags);
+}
+EXPORT_SYMBOL_GPL(nvdimm_is_buffered);
+
 void __exit nd_region_devs_exit(void)
 {
 	ida_destroy(&region_ida);
diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
index 51f5349..901767b 100644
--- a/drivers/virtio/pmem.c
+++ b/drivers/virtio/pmem.c
@@ -81,6 +81,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	ndr_desc.numa_node = nid;
 	ndr_desc.flush = virtio_pmem_flush;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+	set_bit(ND_REGION_BUFFERED, &ndr_desc.flags);
 	nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc);
 	nd_region->provider_data =  dev_to_virtio
 					(nd_region->dev.parent->parent);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0dd316a..d16e03e 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -37,6 +37,8 @@ void put_dax(struct dax_device *dax_dev);
 void kill_dax(struct dax_device *dax_dev);
 void dax_write_cache(struct dax_device *dax_dev, bool wc);
 bool dax_write_cache_enabled(struct dax_device *dax_dev);
+void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc);
+bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev);
 #else
 static inline struct dax_device *dax_get_by_host(const char *host)
 {
@@ -64,6 +66,13 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
 {
 	return false;
 }
+static inline void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
+{
+}
+static inline bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
+{
+	return false;
+}
 #endif
 
 struct writeback_control;
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index ca8bc07..94616f1 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -64,6 +64,11 @@ enum {
 	 */
 	ND_REGION_PERSIST_MEMCTRL = 2,
 
+	/* provides virtio based asynchronous flush mechanism for buffered
+	 * host page cache.
+	 */
+	ND_REGION_BUFFERED = 3,
+
 	/* mark newly adjusted resources as requiring a label update */
 	DPA_RESOURCE_ADJUSTED = 1 << 0,
 };
@@ -265,6 +270,7 @@ int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 int nvdimm_in_overwrite(struct nvdimm *nvdimm);
+int nvdimm_is_buffered(struct nd_region *nd_region);
 
 static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 		unsigned int buf_len, int *cmd_rc)
-- 
2.9.3

Re: [Qemu-devel] [PATCH v3 0/5] kvm "virtio pmem" device

[Pankaj Gupta]

Please ignore this series as my network went down while 
sending this. I will send this series again.

Thanks,
Pankaj  

> 
> This patch series has implementation for "virtio pmem".
>  "virtio pmem" is fake persistent memory(nvdimm) in guest
>  which allows to bypass the guest page cache. This also
>  implements a VIRTIO based asynchronous flush mechanism.
>  
>  Sharing guest kernel driver in this patchset with the
>  changes suggested in v2. Tested with Qemu side device
>  emulation for virtio-pmem [6].
>  
>  Details of project idea for 'virtio pmem' flushing interface
>  is shared [3] & [4].
> 
>  Implementation is divided into two parts:
>  New virtio pmem guest driver and qemu code changes for new
>  virtio pmem paravirtualized device.
> 
> 1. Guest virtio-pmem kernel driver
> ---------------------------------
>    - Reads persistent memory range from paravirt device and
>      registers with 'nvdimm_bus'.
>    - 'nvdimm/pmem' driver uses this information to allocate
>      persistent memory region and setup filesystem operations
>      to the allocated memory.
>    - virtio pmem driver implements asynchronous flushing
>      interface to flush from guest to host.
> 
> 2. Qemu virtio-pmem device
> ---------------------------------
>    - Creates virtio pmem device and exposes a memory range to
>      KVM guest.
>    - At host side this is file backed memory which acts as
>      persistent memory.
>    - Qemu side flush uses aio thread pool API's and virtio
>      for asynchronous guest multi request handling.
> 
>    David Hildenbrand CCed also posted a modified version[6] of
>    qemu virtio-pmem code based on updated Qemu memory device API.
> 
>  Virtio-pmem errors handling:
>  ----------------------------------------
>   Checked behaviour of virtio-pmem for below types of errors
>   Need suggestions on expected behaviour for handling these errors?
> 
>   - Hardware Errors: Uncorrectable recoverable Errors:
>   a] virtio-pmem:
>     - As per current logic if error page belongs to Qemu process,
>       host MCE handler isolates(hwpoison) that page and send SIGBUS.
>       Qemu SIGBUS handler injects exception to KVM guest.
>     - KVM guest then isolates the page and send SIGBUS to guest
>       userspace process which has mapped the page.
>   
>   b] Existing implementation for ACPI pmem driver:
>     - Handles such errors with MCE notifier and creates a list
>       of bad blocks. Read/direct access DAX operation return EIO
>       if accessed memory page fall in bad block list.
>     - It also starts backgound scrubbing.
>     - Similar functionality can be reused in virtio-pmem with MCE
>       notifier but without scrubbing(no ACPI/ARS)? Need inputs to
>       confirm if this behaviour is ok or needs any change?
> 
> Changes from PATCH v2: [1]
> - Disable MAP_SYNC for ext4 & XFS filesystems - [Dan]
> - Use name 'virtio pmem' in place of 'fake dax'
> 
> Changes from PATCH v1: [2]
> - 0-day build test for build dependency on libnvdimm
> 
>  Changes suggested by - [Dan Williams]
> - Split the driver into two parts virtio & pmem
> - Move queuing of async block request to block layer
> - Add "sync" parameter in nvdimm_flush function
> - Use indirect call for nvdimm_flush
> - Don’t move declarations to common global header e.g nd.h
> - nvdimm_flush() return 0 or -EIO if it fails
> - Teach nsio_rw_bytes() that the flush can fail
> - Rename nvdimm_flush() to generic_nvdimm_flush()
> - Use 'nd_region->provider_data' for long dereferencing
> - Remove virtio_pmem_freeze/restore functions
> - Remove BSD license text with SPDX license text
> 
> - Add might_sleep() in virtio_pmem_flush - [Luiz]
> - Make spin_lock_irqsave() narrow
> 
> Changes from RFC v3
> - Rebase to latest upstream - Luiz
> - Call ndregion->flush in place of nvdimm_flush- Luiz
> - kmalloc return check - Luiz
> - virtqueue full handling - Stefan
> - Don't map entire virtio_pmem_req to device - Stefan
> - request leak, correct sizeof req- Stefan
> - Move declaration to virtio_pmem.c
> 
> Changes from RFC v2:
> - Add flush function in the nd_region in place of switching
>   on a flag - Dan & Stefan
> - Add flush completion function with proper locking and wait
>   for host side flush completion - Stefan & Dan
> - Keep userspace API in uapi header file - Stefan, MST
> - Use LE fields & New device id - MST
> - Indentation & spacing suggestions - MST & Eric
> - Remove extra header files & add licensing - Stefan
> 
> Changes from RFC v1:
> - Reuse existing 'pmem' code for registering persistent
>   memory and other operations instead of creating an entirely
>   new block driver.
> - Use VIRTIO driver to register memory information with
>   nvdimm_bus and create region_type accordingly.
> - Call VIRTIO flush from existing pmem driver.
> 
> Pankaj Gupta (5):
>    libnvdimm: nd_region flush callback support
>    virtio-pmem: Add virtio-pmem guest driver
>    libnvdimm: add nd_region buffered dax_dev flag
>    ext4: disable map_sync for virtio pmem
>    xfs: disable map_sync for virtio pmem
> 
> [2] https://lkml.org/lkml/2018/8/31/407
> [3] https://www.spinics.net/lists/kvm/msg149761.html
> [4] https://www.spinics.net/lists/kvm/msg153095.html
> [5] https://lkml.org/lkml/2018/8/31/413
> [6] https://marc.info/?l=qemu-devel&m=153555721901824&w=2
> 
>  drivers/acpi/nfit/core.c         |    4 -
>  drivers/dax/super.c              |   17 +++++
>  drivers/nvdimm/claim.c           |    6 +
>  drivers/nvdimm/nd.h              |    1
>  drivers/nvdimm/pmem.c            |   15 +++-
>  drivers/nvdimm/region_devs.c     |   45 +++++++++++++-
>  drivers/nvdimm/virtio_pmem.c     |   84 ++++++++++++++++++++++++++
>  drivers/virtio/Kconfig           |   10 +++
>  drivers/virtio/Makefile          |    1
>  drivers/virtio/pmem.c            |  125
>  +++++++++++++++++++++++++++++++++++++++
>  fs/ext4/file.c                   |   11 +++
>  fs/xfs/xfs_file.c                |    8 ++
>  include/linux/dax.h              |    9 ++
>  include/linux/libnvdimm.h        |   11 +++
>  include/linux/virtio_pmem.h      |   60 ++++++++++++++++++
>  include/uapi/linux/virtio_ids.h  |    1
>  include/uapi/linux/virtio_pmem.h |   10 +++
>  17 files changed, 406 insertions(+), 12 deletions(-)
> 
> 
> 

Re: [Qemu-devel] [PATCH v3 0/5] kvm "virtio pmem" device

[Pankaj Gupta]

Please ignore this series as my network went down while 
sending this. I will send this series again.

Thanks,
Pankaj  

> 
> This patch series has implementation for "virtio pmem".
>  "virtio pmem" is fake persistent memory(nvdimm) in guest
>  which allows to bypass the guest page cache. This also
>  implements a VIRTIO based asynchronous flush mechanism.
>  
>  Sharing guest kernel driver in this patchset with the
>  changes suggested in v2. Tested with Qemu side device
>  emulation for virtio-pmem [6].
>  
>  Details of project idea for 'virtio pmem' flushing interface
>  is shared [3] & [4].
> 
>  Implementation is divided into two parts:
>  New virtio pmem guest driver and qemu code changes for new
>  virtio pmem paravirtualized device.
> 
> 1. Guest virtio-pmem kernel driver
> ---------------------------------
>    - Reads persistent memory range from paravirt device and
>      registers with 'nvdimm_bus'.
>    - 'nvdimm/pmem' driver uses this information to allocate
>      persistent memory region and setup filesystem operations
>      to the allocated memory.
>    - virtio pmem driver implements asynchronous flushing
>      interface to flush from guest to host.
> 
> 2. Qemu virtio-pmem device
> ---------------------------------
>    - Creates virtio pmem device and exposes a memory range to
>      KVM guest.
>    - At host side this is file backed memory which acts as
>      persistent memory.
>    - Qemu side flush uses aio thread pool API's and virtio
>      for asynchronous guest multi request handling.
> 
>    David Hildenbrand CCed also posted a modified version[6] of
>    qemu virtio-pmem code based on updated Qemu memory device API.
> 
>  Virtio-pmem errors handling:
>  ----------------------------------------
>   Checked behaviour of virtio-pmem for below types of errors
>   Need suggestions on expected behaviour for handling these errors?
> 
>   - Hardware Errors: Uncorrectable recoverable Errors:
>   a] virtio-pmem:
>     - As per current logic if error page belongs to Qemu process,
>       host MCE handler isolates(hwpoison) that page and send SIGBUS.
>       Qemu SIGBUS handler injects exception to KVM guest.
>     - KVM guest then isolates the page and send SIGBUS to guest
>       userspace process which has mapped the page.
>   
>   b] Existing implementation for ACPI pmem driver:
>     - Handles such errors with MCE notifier and creates a list
>       of bad blocks. Read/direct access DAX operation return EIO
>       if accessed memory page fall in bad block list.
>     - It also starts backgound scrubbing.
>     - Similar functionality can be reused in virtio-pmem with MCE
>       notifier but without scrubbing(no ACPI/ARS)? Need inputs to
>       confirm if this behaviour is ok or needs any change?
> 
> Changes from PATCH v2: [1]
> - Disable MAP_SYNC for ext4 & XFS filesystems - [Dan]
> - Use name 'virtio pmem' in place of 'fake dax'
> 
> Changes from PATCH v1: [2]
> - 0-day build test for build dependency on libnvdimm
> 
>  Changes suggested by - [Dan Williams]
> - Split the driver into two parts virtio & pmem
> - Move queuing of async block request to block layer
> - Add "sync" parameter in nvdimm_flush function
> - Use indirect call for nvdimm_flush
> - Don’t move declarations to common global header e.g nd.h
> - nvdimm_flush() return 0 or -EIO if it fails
> - Teach nsio_rw_bytes() that the flush can fail
> - Rename nvdimm_flush() to generic_nvdimm_flush()
> - Use 'nd_region->provider_data' for long dereferencing
> - Remove virtio_pmem_freeze/restore functions
> - Remove BSD license text with SPDX license text
> 
> - Add might_sleep() in virtio_pmem_flush - [Luiz]
> - Make spin_lock_irqsave() narrow
> 
> Changes from RFC v3
> - Rebase to latest upstream - Luiz
> - Call ndregion->flush in place of nvdimm_flush- Luiz
> - kmalloc return check - Luiz
> - virtqueue full handling - Stefan
> - Don't map entire virtio_pmem_req to device - Stefan
> - request leak, correct sizeof req- Stefan
> - Move declaration to virtio_pmem.c
> 
> Changes from RFC v2:
> - Add flush function in the nd_region in place of switching
>   on a flag - Dan & Stefan
> - Add flush completion function with proper locking and wait
>   for host side flush completion - Stefan & Dan
> - Keep userspace API in uapi header file - Stefan, MST
> - Use LE fields & New device id - MST
> - Indentation & spacing suggestions - MST & Eric
> - Remove extra header files & add licensing - Stefan
> 
> Changes from RFC v1:
> - Reuse existing 'pmem' code for registering persistent
>   memory and other operations instead of creating an entirely
>   new block driver.
> - Use VIRTIO driver to register memory information with
>   nvdimm_bus and create region_type accordingly.
> - Call VIRTIO flush from existing pmem driver.
> 
> Pankaj Gupta (5):
>    libnvdimm: nd_region flush callback support
>    virtio-pmem: Add virtio-pmem guest driver
>    libnvdimm: add nd_region buffered dax_dev flag
>    ext4: disable map_sync for virtio pmem
>    xfs: disable map_sync for virtio pmem
> 
> [2] https://lkml.org/lkml/2018/8/31/407
> [3] https://www.spinics.net/lists/kvm/msg149761.html
> [4] https://www.spinics.net/lists/kvm/msg153095.html
> [5] https://lkml.org/lkml/2018/8/31/413
> [6] https://marc.info/?l=qemu-devel&m=153555721901824&w=2
> 
>  drivers/acpi/nfit/core.c         |    4 -
>  drivers/dax/super.c              |   17 +++++
>  drivers/nvdimm/claim.c           |    6 +
>  drivers/nvdimm/nd.h              |    1
>  drivers/nvdimm/pmem.c            |   15 +++-
>  drivers/nvdimm/region_devs.c     |   45 +++++++++++++-
>  drivers/nvdimm/virtio_pmem.c     |   84 ++++++++++++++++++++++++++
>  drivers/virtio/Kconfig           |   10 +++
>  drivers/virtio/Makefile          |    1
>  drivers/virtio/pmem.c            |  125
>  +++++++++++++++++++++++++++++++++++++++
>  fs/ext4/file.c                   |   11 +++
>  fs/xfs/xfs_file.c                |    8 ++
>  include/linux/dax.h              |    9 ++
>  include/linux/libnvdimm.h        |   11 +++
>  include/linux/virtio_pmem.h      |   60 ++++++++++++++++++
>  include/uapi/linux/virtio_ids.h  |    1
>  include/uapi/linux/virtio_pmem.h |   10 +++
>  17 files changed, 406 insertions(+), 12 deletions(-)
> 
> 
> 
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Dan Williams]

On Wed, Jan 9, 2019 at 5:53 AM Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>
> This patch adds 'DAXDEV_BUFFERED' flag which is set
> for virtio pmem corresponding nd_region. This later
> is used to disable MAP_SYNC functionality for ext4
> & xfs filesystem.
>
> Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/dax/super.c          | 17 +++++++++++++++++
>  drivers/nvdimm/pmem.c        |  3 +++
>  drivers/nvdimm/region_devs.c |  7 +++++++
>  drivers/virtio/pmem.c        |  1 +
>  include/linux/dax.h          |  9 +++++++++
>  include/linux/libnvdimm.h    |  6 ++++++
>  6 files changed, 43 insertions(+)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f3..9128740 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -167,6 +167,8 @@ enum dax_device_flags {
>         DAXDEV_ALIVE,
>         /* gate whether dax_flush() calls the low level flush routine */
>         DAXDEV_WRITE_CACHE,
> +       /* flag to disable MAP_SYNC for virtio based host page cache flush */
> +       DAXDEV_BUFFERED,
>  };
>
>  /**
> @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
>  }
>  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
>
> +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> +{
> +       if (wc)
> +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +       else
> +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);

The "write_cache" property was structured this way because it can
conceivably change at runtime. The MAP_SYNC capability should be
static and never changed after init.

> +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> +{
> +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);

Echoing Darrick and Jan this is should be a generic property of a
dax_device and not specific to virtio. I don't like the "buffered"
designation as that's not accurate. There may be hardware reasons why
a dax_device is not synchronous, like a requirement to flush a
write-pending queue or otherwise notify the device of new writes.

I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
would also modify alloc_dax() to take a flags argument so that the
capability can be instantiated when the dax_device is allocated.

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Dan Williams]

On Wed, Jan 9, 2019 at 5:53 AM Pankaj Gupta <pagupta@redhat.com> wrote:
>
> This patch adds 'DAXDEV_BUFFERED' flag which is set
> for virtio pmem corresponding nd_region. This later
> is used to disable MAP_SYNC functionality for ext4
> & xfs filesystem.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  drivers/dax/super.c          | 17 +++++++++++++++++
>  drivers/nvdimm/pmem.c        |  3 +++
>  drivers/nvdimm/region_devs.c |  7 +++++++
>  drivers/virtio/pmem.c        |  1 +
>  include/linux/dax.h          |  9 +++++++++
>  include/linux/libnvdimm.h    |  6 ++++++
>  6 files changed, 43 insertions(+)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f3..9128740 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -167,6 +167,8 @@ enum dax_device_flags {
>         DAXDEV_ALIVE,
>         /* gate whether dax_flush() calls the low level flush routine */
>         DAXDEV_WRITE_CACHE,
> +       /* flag to disable MAP_SYNC for virtio based host page cache flush */
> +       DAXDEV_BUFFERED,
>  };
>
>  /**
> @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
>  }
>  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
>
> +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> +{
> +       if (wc)
> +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +       else
> +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);

The "write_cache" property was structured this way because it can
conceivably change at runtime. The MAP_SYNC capability should be
static and never changed after init.

> +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> +{
> +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);

Echoing Darrick and Jan this is should be a generic property of a
dax_device and not specific to virtio. I don't like the "buffered"
designation as that's not accurate. There may be hardware reasons why
a dax_device is not synchronous, like a requirement to flush a
write-pending queue or otherwise notify the device of new writes.

I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
would also modify alloc_dax() to take a flags argument so that the
capability can be instantiated when the dax_device is allocated.

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Dan Williams]

On Wed, Jan 9, 2019 at 5:53 AM Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>
> This patch adds 'DAXDEV_BUFFERED' flag which is set
> for virtio pmem corresponding nd_region. This later
> is used to disable MAP_SYNC functionality for ext4
> & xfs filesystem.
>
> Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/dax/super.c          | 17 +++++++++++++++++
>  drivers/nvdimm/pmem.c        |  3 +++
>  drivers/nvdimm/region_devs.c |  7 +++++++
>  drivers/virtio/pmem.c        |  1 +
>  include/linux/dax.h          |  9 +++++++++
>  include/linux/libnvdimm.h    |  6 ++++++
>  6 files changed, 43 insertions(+)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f3..9128740 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -167,6 +167,8 @@ enum dax_device_flags {
>         DAXDEV_ALIVE,
>         /* gate whether dax_flush() calls the low level flush routine */
>         DAXDEV_WRITE_CACHE,
> +       /* flag to disable MAP_SYNC for virtio based host page cache flush */
> +       DAXDEV_BUFFERED,
>  };
>
>  /**
> @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
>  }
>  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
>
> +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> +{
> +       if (wc)
> +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +       else
> +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);

The "write_cache" property was structured this way because it can
conceivably change at runtime. The MAP_SYNC capability should be
static and never changed after init.

> +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> +{
> +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);

Echoing Darrick and Jan this is should be a generic property of a
dax_device and not specific to virtio. I don't like the "buffered"
designation as that's not accurate. There may be hardware reasons why
a dax_device is not synchronous, like a requirement to flush a
write-pending queue or otherwise notify the device of new writes.

I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
would also modify alloc_dax() to take a flags argument so that the
capability can be instantiated when the dax_device is allocated.

Re: [Qemu-devel] [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Dan Williams]

On Wed, Jan 9, 2019 at 5:53 AM Pankaj Gupta <pagupta@redhat.com> wrote:
>
> This patch adds 'DAXDEV_BUFFERED' flag which is set
> for virtio pmem corresponding nd_region. This later
> is used to disable MAP_SYNC functionality for ext4
> & xfs filesystem.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  drivers/dax/super.c          | 17 +++++++++++++++++
>  drivers/nvdimm/pmem.c        |  3 +++
>  drivers/nvdimm/region_devs.c |  7 +++++++
>  drivers/virtio/pmem.c        |  1 +
>  include/linux/dax.h          |  9 +++++++++
>  include/linux/libnvdimm.h    |  6 ++++++
>  6 files changed, 43 insertions(+)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f3..9128740 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -167,6 +167,8 @@ enum dax_device_flags {
>         DAXDEV_ALIVE,
>         /* gate whether dax_flush() calls the low level flush routine */
>         DAXDEV_WRITE_CACHE,
> +       /* flag to disable MAP_SYNC for virtio based host page cache flush */
> +       DAXDEV_BUFFERED,
>  };
>
>  /**
> @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
>  }
>  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
>
> +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> +{
> +       if (wc)
> +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +       else
> +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);

The "write_cache" property was structured this way because it can
conceivably change at runtime. The MAP_SYNC capability should be
static and never changed after init.

> +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> +{
> +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);

Echoing Darrick and Jan this is should be a generic property of a
dax_device and not specific to virtio. I don't like the "buffered"
designation as that's not accurate. There may be hardware reasons why
a dax_device is not synchronous, like a requirement to flush a
write-pending queue or otherwise notify the device of new writes.

I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
would also modify alloc_dax() to take a flags argument so that the
capability can be instantiated when the dax_device is allocated.

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Dan Williams]

On Wed, Jan 9, 2019 at 5:53 AM Pankaj Gupta <pagupta@redhat.com> wrote:
>
> This patch adds 'DAXDEV_BUFFERED' flag which is set
> for virtio pmem corresponding nd_region. This later
> is used to disable MAP_SYNC functionality for ext4
> & xfs filesystem.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  drivers/dax/super.c          | 17 +++++++++++++++++
>  drivers/nvdimm/pmem.c        |  3 +++
>  drivers/nvdimm/region_devs.c |  7 +++++++
>  drivers/virtio/pmem.c        |  1 +
>  include/linux/dax.h          |  9 +++++++++
>  include/linux/libnvdimm.h    |  6 ++++++
>  6 files changed, 43 insertions(+)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f3..9128740 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -167,6 +167,8 @@ enum dax_device_flags {
>         DAXDEV_ALIVE,
>         /* gate whether dax_flush() calls the low level flush routine */
>         DAXDEV_WRITE_CACHE,
> +       /* flag to disable MAP_SYNC for virtio based host page cache flush */
> +       DAXDEV_BUFFERED,
>  };
>
>  /**
> @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
>  }
>  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
>
> +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> +{
> +       if (wc)
> +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +       else
> +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);

The "write_cache" property was structured this way because it can
conceivably change at runtime. The MAP_SYNC capability should be
static and never changed after init.

> +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> +{
> +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);

Echoing Darrick and Jan this is should be a generic property of a
dax_device and not specific to virtio. I don't like the "buffered"
designation as that's not accurate. There may be hardware reasons why
a dax_device is not synchronous, like a requirement to flush a
write-pending queue or otherwise notify the device of new writes.

I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
would also modify alloc_dax() to take a flags argument so that the
capability can be instantiated when the dax_device is allocated.

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

> >
> > This patch adds 'DAXDEV_BUFFERED' flag which is set
> > for virtio pmem corresponding nd_region. This later
> > is used to disable MAP_SYNC functionality for ext4
> > & xfs filesystem.
> >
> > Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > ---
> >  drivers/dax/super.c          | 17 +++++++++++++++++
> >  drivers/nvdimm/pmem.c        |  3 +++
> >  drivers/nvdimm/region_devs.c |  7 +++++++
> >  drivers/virtio/pmem.c        |  1 +
> >  include/linux/dax.h          |  9 +++++++++
> >  include/linux/libnvdimm.h    |  6 ++++++
> >  6 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> > index 6e928f3..9128740 100644
> > --- a/drivers/dax/super.c
> > +++ b/drivers/dax/super.c
> > @@ -167,6 +167,8 @@ enum dax_device_flags {
> >         DAXDEV_ALIVE,
> >         /* gate whether dax_flush() calls the low level flush routine */
> >         DAXDEV_WRITE_CACHE,
> > +       /* flag to disable MAP_SYNC for virtio based host page cache flush
> > */
> > +       DAXDEV_BUFFERED,
> >  };
> >
> >  /**
> > @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device
> > *dax_dev)
> >  }
> >  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
> >
> > +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> > +{
> > +       if (wc)
> > +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +       else
> > +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
> 
> The "write_cache" property was structured this way because it can
> conceivably change at runtime. The MAP_SYNC capability should be
> static and never changed after init.

o.k. Will change.

> 
> > +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> > +{
> > +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
> 
> Echoing Darrick and Jan this is should be a generic property of a
> dax_device and not specific to virtio. I don't like the "buffered"
> designation as that's not accurate. There may be hardware reasons why
> a dax_device is not synchronous, like a requirement to flush a
> write-pending queue or otherwise notify the device of new writes.

Agree.

> 
> I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
> would also modify alloc_dax() to take a flags argument so that the
> capability can be instantiated when the dax_device is allocated.

o.k. Will make the change.

Thanks,
Pankaj
> 

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

> >
> > This patch adds 'DAXDEV_BUFFERED' flag which is set
> > for virtio pmem corresponding nd_region. This later
> > is used to disable MAP_SYNC functionality for ext4
> > & xfs filesystem.
> >
> > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> > ---
> >  drivers/dax/super.c          | 17 +++++++++++++++++
> >  drivers/nvdimm/pmem.c        |  3 +++
> >  drivers/nvdimm/region_devs.c |  7 +++++++
> >  drivers/virtio/pmem.c        |  1 +
> >  include/linux/dax.h          |  9 +++++++++
> >  include/linux/libnvdimm.h    |  6 ++++++
> >  6 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> > index 6e928f3..9128740 100644
> > --- a/drivers/dax/super.c
> > +++ b/drivers/dax/super.c
> > @@ -167,6 +167,8 @@ enum dax_device_flags {
> >         DAXDEV_ALIVE,
> >         /* gate whether dax_flush() calls the low level flush routine */
> >         DAXDEV_WRITE_CACHE,
> > +       /* flag to disable MAP_SYNC for virtio based host page cache flush
> > */
> > +       DAXDEV_BUFFERED,
> >  };
> >
> >  /**
> > @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device
> > *dax_dev)
> >  }
> >  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
> >
> > +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> > +{
> > +       if (wc)
> > +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +       else
> > +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
> 
> The "write_cache" property was structured this way because it can
> conceivably change at runtime. The MAP_SYNC capability should be
> static and never changed after init.

o.k. Will change.

> 
> > +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> > +{
> > +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
> 
> Echoing Darrick and Jan this is should be a generic property of a
> dax_device and not specific to virtio. I don't like the "buffered"
> designation as that's not accurate. There may be hardware reasons why
> a dax_device is not synchronous, like a requirement to flush a
> write-pending queue or otherwise notify the device of new writes.

Agree.

> 
> I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
> would also modify alloc_dax() to take a flags argument so that the
> capability can be instantiated when the dax_device is allocated.

o.k. Will make the change.

Thanks,
Pankaj
> 

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

> >
> > This patch adds 'DAXDEV_BUFFERED' flag which is set
> > for virtio pmem corresponding nd_region. This later
> > is used to disable MAP_SYNC functionality for ext4
> > & xfs filesystem.
> >
> > Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > ---
> >  drivers/dax/super.c          | 17 +++++++++++++++++
> >  drivers/nvdimm/pmem.c        |  3 +++
> >  drivers/nvdimm/region_devs.c |  7 +++++++
> >  drivers/virtio/pmem.c        |  1 +
> >  include/linux/dax.h          |  9 +++++++++
> >  include/linux/libnvdimm.h    |  6 ++++++
> >  6 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> > index 6e928f3..9128740 100644
> > --- a/drivers/dax/super.c
> > +++ b/drivers/dax/super.c
> > @@ -167,6 +167,8 @@ enum dax_device_flags {
> >         DAXDEV_ALIVE,
> >         /* gate whether dax_flush() calls the low level flush routine */
> >         DAXDEV_WRITE_CACHE,
> > +       /* flag to disable MAP_SYNC for virtio based host page cache flush
> > */
> > +       DAXDEV_BUFFERED,
> >  };
> >
> >  /**
> > @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device
> > *dax_dev)
> >  }
> >  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
> >
> > +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> > +{
> > +       if (wc)
> > +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +       else
> > +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
> 
> The "write_cache" property was structured this way because it can
> conceivably change at runtime. The MAP_SYNC capability should be
> static and never changed after init.

o.k. Will change.

> 
> > +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> > +{
> > +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
> 
> Echoing Darrick and Jan this is should be a generic property of a
> dax_device and not specific to virtio. I don't like the "buffered"
> designation as that's not accurate. There may be hardware reasons why
> a dax_device is not synchronous, like a requirement to flush a
> write-pending queue or otherwise notify the device of new writes.

Agree.

> 
> I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
> would also modify alloc_dax() to take a flags argument so that the
> capability can be instantiated when the dax_device is allocated.

o.k. Will make the change.

Thanks,
Pankaj
> 

Re: [Qemu-devel] [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

> >
> > This patch adds 'DAXDEV_BUFFERED' flag which is set
> > for virtio pmem corresponding nd_region. This later
> > is used to disable MAP_SYNC functionality for ext4
> > & xfs filesystem.
> >
> > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> > ---
> >  drivers/dax/super.c          | 17 +++++++++++++++++
> >  drivers/nvdimm/pmem.c        |  3 +++
> >  drivers/nvdimm/region_devs.c |  7 +++++++
> >  drivers/virtio/pmem.c        |  1 +
> >  include/linux/dax.h          |  9 +++++++++
> >  include/linux/libnvdimm.h    |  6 ++++++
> >  6 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> > index 6e928f3..9128740 100644
> > --- a/drivers/dax/super.c
> > +++ b/drivers/dax/super.c
> > @@ -167,6 +167,8 @@ enum dax_device_flags {
> >         DAXDEV_ALIVE,
> >         /* gate whether dax_flush() calls the low level flush routine */
> >         DAXDEV_WRITE_CACHE,
> > +       /* flag to disable MAP_SYNC for virtio based host page cache flush
> > */
> > +       DAXDEV_BUFFERED,
> >  };
> >
> >  /**
> > @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device
> > *dax_dev)
> >  }
> >  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
> >
> > +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> > +{
> > +       if (wc)
> > +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +       else
> > +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
> 
> The "write_cache" property was structured this way because it can
> conceivably change at runtime. The MAP_SYNC capability should be
> static and never changed after init.

o.k. Will change.

> 
> > +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> > +{
> > +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
> 
> Echoing Darrick and Jan this is should be a generic property of a
> dax_device and not specific to virtio. I don't like the "buffered"
> designation as that's not accurate. There may be hardware reasons why
> a dax_device is not synchronous, like a requirement to flush a
> write-pending queue or otherwise notify the device of new writes.

Agree.

> 
> I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
> would also modify alloc_dax() to take a flags argument so that the
> capability can be instantiated when the dax_device is allocated.

o.k. Will make the change.

Thanks,
Pankaj
> 

Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag

[Pankaj Gupta]

> >
> > This patch adds 'DAXDEV_BUFFERED' flag which is set
> > for virtio pmem corresponding nd_region. This later
> > is used to disable MAP_SYNC functionality for ext4
> > & xfs filesystem.
> >
> > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> > ---
> >  drivers/dax/super.c          | 17 +++++++++++++++++
> >  drivers/nvdimm/pmem.c        |  3 +++
> >  drivers/nvdimm/region_devs.c |  7 +++++++
> >  drivers/virtio/pmem.c        |  1 +
> >  include/linux/dax.h          |  9 +++++++++
> >  include/linux/libnvdimm.h    |  6 ++++++
> >  6 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> > index 6e928f3..9128740 100644
> > --- a/drivers/dax/super.c
> > +++ b/drivers/dax/super.c
> > @@ -167,6 +167,8 @@ enum dax_device_flags {
> >         DAXDEV_ALIVE,
> >         /* gate whether dax_flush() calls the low level flush routine */
> >         DAXDEV_WRITE_CACHE,
> > +       /* flag to disable MAP_SYNC for virtio based host page cache flush
> > */
> > +       DAXDEV_BUFFERED,
> >  };
> >
> >  /**
> > @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device
> > *dax_dev)
> >  }
> >  EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
> >
> > +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> > +{
> > +       if (wc)
> > +               set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +       else
> > +               clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
> 
> The "write_cache" property was structured this way because it can
> conceivably change at runtime. The MAP_SYNC capability should be
> static and never changed after init.

o.k. Will change.

> 
> > +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> > +{
> > +       return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
> 
> Echoing Darrick and Jan this is should be a generic property of a
> dax_device and not specific to virtio. I don't like the "buffered"
> designation as that's not accurate. There may be hardware reasons why
> a dax_device is not synchronous, like a requirement to flush a
> write-pending queue or otherwise notify the device of new writes.

Agree.

> 
> I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
> would also modify alloc_dax() to take a flags argument so that the
> capability can be instantiated when the dax_device is allocated.

o.k. Will make the change.

Thanks,
Pankaj
> 

[PATCH v3 1/5] libnvdimm: nd_region flush callback support

[Pankaj Gupta]

This patch adds functionality to perform flush from guest
to host over VIRTIO. We are registering a callback based
on 'nd_region' type. virtio_pmem driver requires this special
flush function. For rest of the region types we are registering
existing flush function. Report error returned by host fsync
failure to userspace.

This also handles asynchronous flush requests from the block layer
by creating a child bio and chaining it with parent bio.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/acpi/nfit/core.c     |  4 ++--
 drivers/nvdimm/claim.c       |  6 ++++--
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        | 12 ++++++++----
 drivers/nvdimm/region_devs.c | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/libnvdimm.h    |  5 ++++-
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b072cfc..f154852 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2234,7 +2234,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->addr.base + offset);
-	nvdimm_flush(nfit_blk->nd_region);
+	nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
 		readq(mmio->addr.base + offset);
@@ -2283,7 +2283,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 	}
 
 	if (rw)
-		nvdimm_flush(nfit_blk->nd_region);
+		nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index fb667bf..a1dfa06 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -263,7 +263,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
 	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
 	sector_t sector = offset >> 9;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	if (unlikely(!size))
 		return 0;
@@ -301,7 +301,9 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	memcpy_flushcache(nsio->addr + offset, buf, size);
-	nvdimm_flush(to_nd_region(ndns->dev.parent));
+	ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL, false);
+	if (ret)
+		rc = ret;
 
 	return rc;
 }
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7..d53a2d1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -160,6 +160,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	struct nd_mapping mapping[0];
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct nd_blk_region {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e29..5d6a4a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -192,6 +192,7 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+	int ret = 0;
 	blk_status_t rc = 0;
 	bool do_acct;
 	unsigned long start;
@@ -201,7 +202,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_PREFLUSH)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -216,7 +217,10 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
+
+	if (ret)
+		bio->bi_status = errno_to_blk_status(ret);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
@@ -528,14 +532,14 @@ static int nd_pmem_remove(struct device *dev)
 		sysfs_put(pmem->bb_state);
 		pmem->bb_state = NULL;
 	}
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 
 	return 0;
 }
 
 static void nd_pmem_shutdown(struct device *dev)
 {
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 }
 
 static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afc..5508727 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -290,7 +290,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
 		return rc;
 	if (!flush)
 		return -EINVAL;
-	nvdimm_flush(nd_region);
+	rc = nvdimm_flush(nd_region, NULL, false);
+	if (rc)
+		return rc;
 
 	return len;
 }
@@ -1065,6 +1067,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	if (ndr_desc->flush)
+		nd_region->flush = ndr_desc->flush;
+	else
+		nd_region->flush = generic_nvdimm_flush;
+
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1105,11 +1112,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async)
+{
+	int rc = 0;
+
+	/* Create child bio for asynchronous flush and chain with
+	 * parent bio. Otherwise directly call nd_region flush.
+	 */
+	if (async && bio->bi_iter.bi_sector != -1) {
+
+		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
+
+		if (!child)
+			return -ENOMEM;
+		bio_copy_dev(child, bio);
+		child->bi_opf = REQ_PREFLUSH;
+		child->bi_iter.bi_sector = -1;
+		bio_chain(child, bio);
+		submit_bio(child);
+	} else {
+		if (nd_region->flush(nd_region))
+			rc = -EIO;
+	}
+
+	return rc;
+}
 /**
  * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  * @nd_region: blk or interleaved pmem region
  */
-void nvdimm_flush(struct nd_region *nd_region)
+int generic_nvdimm_flush(struct nd_region *nd_region)
 {
 	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
 	int i, idx;
@@ -1133,6 +1165,8 @@ void nvdimm_flush(struct nd_region *nd_region)
 		if (ndrd_get_flush_wpq(ndrd, i, 0))
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..b49632c 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -115,6 +115,7 @@ struct nd_mapping_desc {
 	int position;
 };
 
+struct nd_region;
 struct nd_region_desc {
 	struct resource *res;
 	struct nd_mapping_desc *mapping;
@@ -126,6 +127,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct device;
@@ -201,7 +203,8 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async);
+int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3

[PATCH v3 1/5] libnvdimm: nd_region flush callback support

[Pankaj Gupta]

This patch adds functionality to perform flush from guest
to host over VIRTIO. We are registering a callback based
on 'nd_region' type. virtio_pmem driver requires this special
flush function. For rest of the region types we are registering
existing flush function. Report error returned by host fsync
failure to userspace.

This also handles asynchronous flush requests from the block layer
by creating a child bio and chaining it with parent bio.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/acpi/nfit/core.c     |  4 ++--
 drivers/nvdimm/claim.c       |  6 ++++--
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        | 12 ++++++++----
 drivers/nvdimm/region_devs.c | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/libnvdimm.h    |  5 ++++-
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b072cfc..f154852 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2234,7 +2234,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->addr.base + offset);
-	nvdimm_flush(nfit_blk->nd_region);
+	nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
 		readq(mmio->addr.base + offset);
@@ -2283,7 +2283,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 	}
 
 	if (rw)
-		nvdimm_flush(nfit_blk->nd_region);
+		nvdimm_flush(nfit_blk->nd_region, NULL, false);
 
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index fb667bf..a1dfa06 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -263,7 +263,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
 	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
 	sector_t sector = offset >> 9;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	if (unlikely(!size))
 		return 0;
@@ -301,7 +301,9 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	memcpy_flushcache(nsio->addr + offset, buf, size);
-	nvdimm_flush(to_nd_region(ndns->dev.parent));
+	ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL, false);
+	if (ret)
+		rc = ret;
 
 	return rc;
 }
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7..d53a2d1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -160,6 +160,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	struct nd_mapping mapping[0];
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct nd_blk_region {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e29..5d6a4a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -192,6 +192,7 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+	int ret = 0;
 	blk_status_t rc = 0;
 	bool do_acct;
 	unsigned long start;
@@ -201,7 +202,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_PREFLUSH)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -216,7 +217,10 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		ret = nvdimm_flush(nd_region, bio, true);
+
+	if (ret)
+		bio->bi_status = errno_to_blk_status(ret);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
@@ -528,14 +532,14 @@ static int nd_pmem_remove(struct device *dev)
 		sysfs_put(pmem->bb_state);
 		pmem->bb_state = NULL;
 	}
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 
 	return 0;
 }
 
 static void nd_pmem_shutdown(struct device *dev)
 {
-	nvdimm_flush(to_nd_region(dev->parent));
+	nvdimm_flush(to_nd_region(dev->parent), NULL, false);
 }
 
 static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afc..5508727 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -290,7 +290,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
 		return rc;
 	if (!flush)
 		return -EINVAL;
-	nvdimm_flush(nd_region);
+	rc = nvdimm_flush(nd_region, NULL, false);
+	if (rc)
+		return rc;
 
 	return len;
 }
@@ -1065,6 +1067,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	if (ndr_desc->flush)
+		nd_region->flush = ndr_desc->flush;
+	else
+		nd_region->flush = generic_nvdimm_flush;
+
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1105,11 +1112,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async)
+{
+	int rc = 0;
+
+	/* Create child bio for asynchronous flush and chain with
+	 * parent bio. Otherwise directly call nd_region flush.
+	 */
+	if (async && bio->bi_iter.bi_sector != -1) {
+
+		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
+
+		if (!child)
+			return -ENOMEM;
+		bio_copy_dev(child, bio);
+		child->bi_opf = REQ_PREFLUSH;
+		child->bi_iter.bi_sector = -1;
+		bio_chain(child, bio);
+		submit_bio(child);
+	} else {
+		if (nd_region->flush(nd_region))
+			rc = -EIO;
+	}
+
+	return rc;
+}
 /**
  * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  * @nd_region: blk or interleaved pmem region
  */
-void nvdimm_flush(struct nd_region *nd_region)
+int generic_nvdimm_flush(struct nd_region *nd_region)
 {
 	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
 	int i, idx;
@@ -1133,6 +1165,8 @@ void nvdimm_flush(struct nd_region *nd_region)
 		if (ndrd_get_flush_wpq(ndrd, i, 0))
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..b49632c 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -115,6 +115,7 @@ struct nd_mapping_desc {
 	int position;
 };
 
+struct nd_region;
 struct nd_region_desc {
 	struct resource *res;
 	struct nd_mapping_desc *mapping;
@@ -126,6 +127,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct nd_region *nd_region);
 };
 
 struct device;
@@ -201,7 +203,8 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async);
+int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3