[PATCH 0/3] Correctness fixes for NFIT BLK I/O path

[PATCH 0/3] Correctness fixes for NFIT BLK I/O path

[Ross Zwisler]

Patch 1 is just a quick update to MAINTAINERS for include/linux/pmem.h.

Patches 2 and 3 in this series contain correctness fixes for the NFIT BLK I/O
path, which in my opinion need to be pulled in for v4.2.  These fixes include
making sure that the block control registers are properly flushed before the
associated apertures are accessed, which is necessary for proper operation.
This series also updates the I/O path to use non-temporal stores, and to
respect the "latch" flag outlined in the DSM specification.

Ross Zwisler (3):
  pmem: add maintainer for include/linux/pmem.h
  nfit: update block I/O path to use PMEM API
  nfit: add support for NVDIMM "latch" flag

 MAINTAINERS         |   1 +
 drivers/acpi/nfit.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++---
 drivers/acpi/nfit.h |  16 +++++++-
 3 files changed, 125 insertions(+), 6 deletions(-)

-- 
1.9.3

[PATCH 1/3] pmem: add maintainer for include/linux/pmem.h

[Ross Zwisler]

The file include/linux/pmem.h was recently created to hold the PMEM API,
and is logically part of the PMEM driver.  Add an entry for this file to
MAINTAINERS.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Greg KH <gregkh@linuxfoundation.org> 
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org
---
 MAINTAINERS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index d4164f80cb42..8f0826b2c036 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5952,6 +5952,7 @@ L:	linux-nvdimm@lists.01.org
 Q:	https://patchwork.kernel.org/project/linux-nvdimm/list/
 S:	Supported
 F:	drivers/nvdimm/pmem.c
+F:	include/linux/pmem.h
 
 LINUX FOR IBM pSERIES (RS/6000)
 M:	Paul Mackerras <paulus@au.ibm.com>
-- 
1.9.3

[PATCH 2/3] nfit: update block I/O path to use PMEM API

[Ross Zwisler]

Update the nfit block I/O path to use the new PMEM API and to adhere to
the read/write flows outlined in the "NVDIMM Block Window Driver
Writer's Guide":

http://pmem.io/documents/NVDIMM_Driver_Writers_Guide.pdf

This includes adding support for targeted NVDIMM flushes called "flush
hints" in the ACPI 6.0 specification:

http://www.uefi.org/sites/default/files/resources/ACPI_6.0.pdf

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: linux-nvdimm@lists.01.org
Cc: linux-acpi@vger.kernel.org
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Toshi Kani <toshi.kani@hp.com>
---
 drivers/acpi/nfit.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++---
 drivers/acpi/nfit.h | 10 ++++++-
 2 files changed, 86 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
index a20b7c883ca0..b3c446412f61 100644
--- a/drivers/acpi/nfit.c
+++ b/drivers/acpi/nfit.c
@@ -18,6 +18,7 @@
 #include <linux/list.h>
 #include <linux/acpi.h>
 #include <linux/sort.h>
+#include <linux/pmem.h>
 #include <linux/io.h>
 #include "nfit.h"
 
@@ -305,6 +306,23 @@ static bool add_idt(struct acpi_nfit_desc *acpi_desc,
 	return true;
 }
 
+static bool add_flush(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_flush_address *flush)
+{
+	struct device *dev = acpi_desc->dev;
+	struct nfit_flush *nfit_flush = devm_kzalloc(dev, sizeof(*nfit_flush),
+			GFP_KERNEL);
+
+	if (!nfit_flush)
+		return false;
+	INIT_LIST_HEAD(&nfit_flush->list);
+	nfit_flush->flush = flush;
+	list_add_tail(&nfit_flush->list, &acpi_desc->flushes);
+	dev_dbg(dev, "%s: nfit_flush handle: %d hint_count: %d\n", __func__,
+			flush->device_handle, flush->hint_count);
+	return true;
+}
+
 static void *add_table(struct acpi_nfit_desc *acpi_desc, void *table,
 		const void *end)
 {
@@ -338,7 +356,8 @@ static void *add_table(struct acpi_nfit_desc *acpi_desc, void *table,
 			return err;
 		break;
 	case ACPI_NFIT_TYPE_FLUSH_ADDRESS:
-		dev_dbg(dev, "%s: flush\n", __func__);
+		if (!add_flush(acpi_desc, table))
+			return err;
 		break;
 	case ACPI_NFIT_TYPE_SMBIOS:
 		dev_dbg(dev, "%s: smbios\n", __func__);
@@ -389,6 +408,7 @@ static int nfit_mem_add(struct acpi_nfit_desc *acpi_desc,
 {
 	u16 dcr = __to_nfit_memdev(nfit_mem)->region_index;
 	struct nfit_memdev *nfit_memdev;
+	struct nfit_flush *nfit_flush;
 	struct nfit_dcr *nfit_dcr;
 	struct nfit_bdw *nfit_bdw;
 	struct nfit_idt *nfit_idt;
@@ -442,6 +462,14 @@ static int nfit_mem_add(struct acpi_nfit_desc *acpi_desc,
 			nfit_mem->idt_bdw = nfit_idt->idt;
 			break;
 		}
+
+		list_for_each_entry(nfit_flush, &acpi_desc->flushes, list) {
+			if (nfit_flush->flush->device_handle !=
+					nfit_memdev->memdev->device_handle)
+				continue;
+			nfit_mem->nfit_flush = nfit_flush;
+			break;
+		}
 		break;
 	}
 
@@ -978,6 +1006,24 @@ static u64 to_interleave_offset(u64 offset, struct nfit_blk_mmio *mmio)
 	return mmio->base_offset + line_offset + table_offset + sub_line_offset;
 }
 
+static void wmb_blk(struct nfit_blk *nfit_blk)
+{
+
+	if (nfit_blk->nvdimm_flush) {
+		/*
+		 * The first wmb() is needed to 'sfence' all previous writes
+		 * such that they are architecturally visible for the platform
+		 * buffer flush.  Note that we've already arranged for pmem
+		 * writes to avoid the cache via arch_memcpy_to_pmem().  The
+		 * final wmb() ensures ordering for the NVDIMM flush write.
+		 */
+		wmb();
+		writeq(1, nfit_blk->nvdimm_flush);
+		wmb();
+	} else
+		wmb_pmem();
+}
+
 static u64 read_blk_stat(struct nfit_blk *nfit_blk, unsigned int bw)
 {
 	struct nfit_blk_mmio *mmio = &nfit_blk->mmio[DCR];
@@ -1012,6 +1058,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 		offset = to_interleave_offset(offset, mmio);
 
 	writeq(cmd, mmio->base + offset);
+	wmb_blk(nfit_blk);
 	/* FIXME: conditionally perform read-back if mandated by firmware */
 }
 
@@ -1026,7 +1073,6 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 
 	base_offset = nfit_blk->bdw_offset + dpa % L1_CACHE_BYTES
 		+ lane * mmio->size;
-	/* TODO: non-temporal access, flush hints, cache management etc... */
 	write_blk_ctl(nfit_blk, lane, dpa, len, rw);
 	while (len) {
 		unsigned int c;
@@ -1045,13 +1091,19 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
 		}
 
 		if (rw)
-			memcpy(mmio->aperture + offset, iobuf + copied, c);
+			memcpy_to_pmem(mmio->aperture + offset,
+					iobuf + copied, c);
 		else
-			memcpy(iobuf + copied, mmio->aperture + offset, c);
+			memcpy_from_pmem(iobuf + copied,
+					mmio->aperture + offset, c);
 
 		copied += c;
 		len -= c;
 	}
+
+	if (rw)
+		wmb_blk(nfit_blk);
+
 	rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
 	return rc;
 }
@@ -1212,12 +1264,16 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
 	struct nvdimm_bus_descriptor *nd_desc = to_nd_desc(nvdimm_bus);
 	struct acpi_nfit_desc *acpi_desc = to_acpi_desc(nd_desc);
 	struct nd_blk_region *ndbr = to_nd_blk_region(dev);
+	struct nfit_flush *nfit_flush;
 	struct nfit_blk_mmio *mmio;
 	struct nfit_blk *nfit_blk;
 	struct nfit_mem *nfit_mem;
 	struct nvdimm *nvdimm;
 	int rc;
 
+	if (!arch_has_pmem_api())
+		dev_warn(dev, "unable to guarantee persistence of writes\n");
+
 	nvdimm = nd_blk_region_to_dimm(ndbr);
 	nfit_mem = nvdimm_provider_data(nvdimm);
 	if (!nfit_mem || !nfit_mem->dcr || !nfit_mem->bdw) {
@@ -1277,6 +1333,22 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
 		return rc;
 	}
 
+	nfit_flush = nfit_mem->nfit_flush;
+	if (nfit_flush && nfit_flush->flush->hint_count != 0) {
+		struct acpi_nfit_flush_address *flush = nfit_flush->flush;
+		struct resource res;
+
+		res.start = flush->hint_address[0];
+		res.end = flush->hint_address[0] + sizeof(u64) - 1;
+		res.name = dev_name(dev);
+		res.flags = IORESOURCE_MEM;
+
+		/* only need a single NVDIMM flush address.  map uncacheable */
+		nfit_blk->nvdimm_flush = devm_ioremap_resource(dev, &res);
+		if (IS_ERR(nfit_blk->nvdimm_flush))
+			return -ENOMEM;
+	}
+
 	if (mmio->line_size == 0)
 		return 0;
 
@@ -1459,6 +1531,7 @@ int acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, acpi_size sz)
 	INIT_LIST_HEAD(&acpi_desc->dcrs);
 	INIT_LIST_HEAD(&acpi_desc->bdws);
 	INIT_LIST_HEAD(&acpi_desc->idts);
+	INIT_LIST_HEAD(&acpi_desc->flushes);
 	INIT_LIST_HEAD(&acpi_desc->memdevs);
 	INIT_LIST_HEAD(&acpi_desc->dimms);
 	mutex_init(&acpi_desc->spa_map_mutex);
diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
index 81f2e8c5a79c..d284729cc37c 100644
--- a/drivers/acpi/nfit.h
+++ b/drivers/acpi/nfit.h
@@ -60,6 +60,11 @@ struct nfit_idt {
 	struct list_head list;
 };
 
+struct nfit_flush {
+	struct acpi_nfit_flush_address *flush;
+	struct list_head list;
+};
+
 struct nfit_memdev {
 	struct acpi_nfit_memory_map *memdev;
 	struct list_head list;
@@ -77,6 +82,7 @@ struct nfit_mem {
 	struct acpi_nfit_system_address *spa_bdw;
 	struct acpi_nfit_interleave *idt_dcr;
 	struct acpi_nfit_interleave *idt_bdw;
+	struct nfit_flush *nfit_flush;
 	struct list_head list;
 	struct acpi_device *adev;
 	unsigned long dsm_mask;
@@ -88,6 +94,7 @@ struct acpi_nfit_desc {
 	struct mutex spa_map_mutex;
 	struct list_head spa_maps;
 	struct list_head memdevs;
+	struct list_head flushes;
 	struct list_head dimms;
 	struct list_head spas;
 	struct list_head dcrs;
@@ -109,7 +116,7 @@ struct nfit_blk {
 	struct nfit_blk_mmio {
 		union {
 			void __iomem *base;
-			void *aperture;
+			void __pmem  *aperture;
 		};
 		u64 size;
 		u64 base_offset;
@@ -123,6 +130,7 @@ struct nfit_blk {
 	u64 bdw_offset; /* post interleave offset */
 	u64 stat_offset;
 	u64 cmd_offset;
+	void __iomem *nvdimm_flush;
 };
 
 struct nfit_spa_mapping {
-- 
1.9.3

[PATCH 3/3] nfit: add support for NVDIMM "latch" flag

[Ross Zwisler]

Add support in the NFIT BLK I/O path for the "latch" flag
defined in the "Get Block NVDIMM Flags" _DSM function:

http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

This flag requires the driver to read back the command register after it
is written in the block I/O path.  This ensures that the hardware has
fully processed the new command and moved the aperture appropriately.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: linux-nvdimm@lists.01.org
Cc: linux-acpi@vger.kernel.org
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Toshi Kani <toshi.kani@hp.com>
---
 drivers/acpi/nfit.c | 33 ++++++++++++++++++++++++++++++++-
 drivers/acpi/nfit.h |  6 ++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
index b3c446412f61..9062c11c1062 100644
--- a/drivers/acpi/nfit.c
+++ b/drivers/acpi/nfit.c
@@ -1059,7 +1059,9 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 
 	writeq(cmd, mmio->base + offset);
 	wmb_blk(nfit_blk);
-	/* FIXME: conditionally perform read-back if mandated by firmware */
+
+	if (nfit_blk->dimm_flags & ND_BLK_DCR_LATCH)
+		readq(mmio->base + offset);
 }
 
 static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
@@ -1258,6 +1260,28 @@ static int nfit_blk_init_interleave(struct nfit_blk_mmio *mmio,
 	return 0;
 }
 
+static int acpi_nfit_blk_get_flags(struct nvdimm_bus_descriptor *nd_desc,
+		struct nvdimm *nvdimm, struct nfit_blk *nfit_blk)
+{
+	struct nd_cmd_dimm_flags flags;
+	int rc;
+
+	memset(&flags, 0, sizeof(flags));
+	rc = nd_desc->ndctl(nd_desc, nvdimm, ND_CMD_DIMM_FLAGS, &flags,
+			sizeof(flags));
+
+	if (rc >= 0) {
+		if (!flags.status)
+			nfit_blk->dimm_flags = flags.flags;
+		else if (flags.status == ND_DSM_STATUS_NOT_SUPPORTED)
+			nfit_blk->dimm_flags = 0; /* as per the _DSM spec */
+		else
+			rc = -EINVAL;
+	}
+
+	return rc;
+}
+
 static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
 		struct device *dev)
 {
@@ -1333,6 +1357,13 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
 		return rc;
 	}
 
+	rc = acpi_nfit_blk_get_flags(nd_desc, nvdimm, nfit_blk);
+	if (rc < 0) {
+		dev_dbg(dev, "%s: %s failed get DIMM flags\n",
+				__func__, nvdimm_name(nvdimm));
+		return rc;
+	}
+
 	nfit_flush = nfit_mem->nfit_flush;
 	if (nfit_flush && nfit_flush->flush->hint_count != 0) {
 		struct acpi_nfit_flush_address *flush = nfit_flush->flush;
diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
index d284729cc37c..98e36ca0dfc2 100644
--- a/drivers/acpi/nfit.h
+++ b/drivers/acpi/nfit.h
@@ -40,6 +40,11 @@ enum nfit_uuids {
 	NFIT_UUID_MAX,
 };
 
+enum {
+	ND_BLK_DCR_LATCH = 2,
+	ND_DSM_STATUS_NOT_SUPPORTED = 1,
+};
+
 struct nfit_spa {
 	struct acpi_nfit_system_address *spa;
 	struct list_head list;
@@ -131,6 +136,7 @@ struct nfit_blk {
 	u64 stat_offset;
 	u64 cmd_offset;
 	void __iomem *nvdimm_flush;
+	u32 dimm_flags;
 };
 
 struct nfit_spa_mapping {
-- 
1.9.3

Re: [PATCH 3/3] nfit: add support for NVDIMM "latch" flag

[Dan Williams]

On Wed, Jul 8, 2015 at 9:00 AM, Ross Zwisler
<ross.zwisler@linux.intel.com> wrote:
> Add support in the NFIT BLK I/O path for the "latch" flag
> defined in the "Get Block NVDIMM Flags" _DSM function:
>
> http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf
>
> This flag requires the driver to read back the command register after it
> is written in the block I/O path.  This ensures that the hardware has
> fully processed the new command and moved the aperture appropriately.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Cc: linux-nvdimm@lists.01.org
> Cc: linux-acpi@vger.kernel.org
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Toshi Kani <toshi.kani@hp.com>
> ---
>  drivers/acpi/nfit.c | 33 ++++++++++++++++++++++++++++++++-
>  drivers/acpi/nfit.h |  6 ++++++
>  2 files changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
> index b3c446412f61..9062c11c1062 100644
> --- a/drivers/acpi/nfit.c
> +++ b/drivers/acpi/nfit.c
> @@ -1059,7 +1059,9 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
>
>         writeq(cmd, mmio->base + offset);
>         wmb_blk(nfit_blk);
> -       /* FIXME: conditionally perform read-back if mandated by firmware */
> +
> +       if (nfit_blk->dimm_flags & ND_BLK_DCR_LATCH)
> +               readq(mmio->base + offset);
>  }
>
>  static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
> @@ -1258,6 +1260,28 @@ static int nfit_blk_init_interleave(struct nfit_blk_mmio *mmio,
>         return 0;
>  }
>
> +static int acpi_nfit_blk_get_flags(struct nvdimm_bus_descriptor *nd_desc,
> +               struct nvdimm *nvdimm, struct nfit_blk *nfit_blk)
> +{
> +       struct nd_cmd_dimm_flags flags;
> +       int rc;
> +
> +       memset(&flags, 0, sizeof(flags));
> +       rc = nd_desc->ndctl(nd_desc, nvdimm, ND_CMD_DIMM_FLAGS, &flags,
> +                       sizeof(flags));
> +
> +       if (rc >= 0) {
> +               if (!flags.status)
> +                       nfit_blk->dimm_flags = flags.flags;

Subjective nit, I tend to prefer the form (flags.status == 0) for
positive cases.  (!flags.status) reads like an error handling case to
me.

> +               else if (flags.status == ND_DSM_STATUS_NOT_SUPPORTED)
> +                       nfit_blk->dimm_flags = 0; /* as per the _DSM spec */

The spec says if command is "not implemented", I would treat "not
supported" like any other non-zero flags.status value and return a
failure.

> +               else
> +                       rc = -EINVAL;

s/EINVAL/ENXIO/ as it is a failure to run the command, not necessarily
bad parameters.

> +       }
> +
> +       return rc;

This ends up treating -ENOTTY as an error when it is really just an
indication that the flags DSM is not implemented.  We should return
zero in that case.

> +}
> +
>  static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
>                 struct device *dev)
>  {
> @@ -1333,6 +1357,13 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
>                 return rc;
>         }
>
> +       rc = acpi_nfit_blk_get_flags(nd_desc, nvdimm, nfit_blk);
> +       if (rc < 0) {
> +               dev_dbg(dev, "%s: %s failed get DIMM flags\n",
> +                               __func__, nvdimm_name(nvdimm));
> +               return rc;
> +       }
> +
>         nfit_flush = nfit_mem->nfit_flush;
>         if (nfit_flush && nfit_flush->flush->hint_count != 0) {
>                 struct acpi_nfit_flush_address *flush = nfit_flush->flush;
> diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
> index d284729cc37c..98e36ca0dfc2 100644
> --- a/drivers/acpi/nfit.h
> +++ b/drivers/acpi/nfit.h
> @@ -40,6 +40,11 @@ enum nfit_uuids {
>         NFIT_UUID_MAX,
>  };
>
> +enum {
> +       ND_BLK_DCR_LATCH = 2,
> +       ND_DSM_STATUS_NOT_SUPPORTED = 1,

Unless it becomes clear that we need this for debug I'd prefer to not
implement the error status flags at this point and just treat non-zero
status flags generically as -ENXIO.

> +};
> +
>  struct nfit_spa {
>         struct acpi_nfit_system_address *spa;
>         struct list_head list;
> @@ -131,6 +136,7 @@ struct nfit_blk {
>         u64 stat_offset;
>         u64 cmd_offset;
>         void __iomem *nvdimm_flush;
> +       u32 dimm_flags;
>  };
>
>  struct nfit_spa_mapping {
> --
> 1.9.3
>

Re: [PATCH 0/3] Correctness fixes for NFIT BLK I/O path

[Rafael J. Wysocki]

On Wednesday, July 08, 2015 10:00:18 AM Ross Zwisler wrote:
> Patch 1 is just a quick update to MAINTAINERS for include/linux/pmem.h.
> 
> Patches 2 and 3 in this series contain correctness fixes for the NFIT BLK I/O
> path, which in my opinion need to be pulled in for v4.2.  These fixes include
> making sure that the block control registers are properly flushed before the
> associated apertures are accessed, which is necessary for proper operation.
> This series also updates the I/O path to use non-temporal stores, and to
> respect the "latch" flag outlined in the DSM specification.
> 
> Ross Zwisler (3):
>   pmem: add maintainer for include/linux/pmem.h
>   nfit: update block I/O path to use PMEM API
>   nfit: add support for NVDIMM "latch" flag
> 
>  MAINTAINERS         |   1 +
>  drivers/acpi/nfit.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++---
>  drivers/acpi/nfit.h |  16 +++++++-
>  3 files changed, 125 insertions(+), 6 deletions(-)

No objections from me and I'm assuming Dan to be taking these.

Thanks,
Rafael