[Qemu-devel] [PATCH V5_resend 0/7] nvdimm: support MAP_SYNC for memory-backend-file

[Qemu-devel] [PATCH V5_resend 0/7] nvdimm: support MAP_SYNC for memory-backend-file

[Zhang Yi]

Linux 4.15 introduces a new mmap flag MAP_SYNC, which can be used to
guarantee the write persistence to mmap'ed files supporting DAX (e.g.,
files on ext4/xfs file system mounted with '-o dax').

A description of MAP_SYNC and MAP_SHARED_VALIDATE can be found at
    https://patchwork.kernel.org/patch/10028151/

In order to make sure that the file metadata is in sync after a fault 
while we are writing a shared DAX supporting backend files, this
patch-set enables QEMU to use MAP_SYNC flag for memory-backend-dax-file.

As the DAX vs DMA truncated issue was solved, we refined the code and
send out this feature for the v5 version.

A new auto on/off option 'sync' is added to memory-backend-file:
 - on:  try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
        'share=off', QEMU will abort
 - off: never pass MAP_SYNC to mmap(2)
 - auto (default): if MAP_SYNC is supported and 'share=on', work as if
        'sync=on'; otherwise, work as if 'sync=off'

Zhang Yi (7):
  numa: Fixed the memory leak of numa error message
  util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter
  exec: switch qemu_ram_alloc_from_{file, fd} to the 'flags' parameter
  util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
  util/mmap-alloc: Switch the RAM_SYNC flags to OnOffAuto
  hostmem: add more information in error messages
  hostmem-file: add 'sync' option

 backends/hostmem-file.c               | 45 +++++++++++++++++++++++++++++++++--
 backends/hostmem.c                    |  8 ++++---
 docs/nvdimm.txt                       | 20 +++++++++++++++-
 exec.c                                |  9 +++----
 include/exec/memory.h                 | 18 ++++++++++++++
 include/exec/ram_addr.h               |  1 +
 include/qemu/mmap-alloc.h             | 20 +++++++++++++++-
 include/standard-headers/linux/mman.h | 44 ++++++++++++++++++++++++++++++++++
 numa.c                                |  1 +
 qemu-options.hx                       | 22 ++++++++++++++++-
 util/mmap-alloc.c                     | 26 ++++++++++++++++----
 util/oslib-posix.c                    |  4 +++-
 12 files changed, 200 insertions(+), 18 deletions(-)
 create mode 100644 include/standard-headers/linux/mman.h

-- 
2.7.4

[Qemu-devel] [PATCH V5_resend 1/7] numa: Fixed the memory leak of numa error message

[Zhang Yi]

object_get_canonical_path_component() returns a string which
must be freed using g_free().

Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
---
 numa.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/numa.c b/numa.c
index 50ec016..3875e1e 100644
--- a/numa.c
+++ b/numa.c
@@ -533,6 +533,7 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
             error_report("memory backend %s is used multiple times. Each "
                          "-numa option must use a different memdev value.",
                          path);
+            g_free(path);
             exit(1);
         }
 
-- 
2.7.4

Re: [Qemu-devel] [PATCH V5_resend 1/7] numa: Fixed the memory leak of numa error message

[Igor Mammedov]

On Tue, 20 Nov 2018 15:48:06 +0800
Zhang Yi <yi.z.zhang@linux.intel.com> wrote:

> object_get_canonical_path_component() returns a string which
> must be freed using g_free().
> 
> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>

Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> ---
>  numa.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/numa.c b/numa.c
> index 50ec016..3875e1e 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -533,6 +533,7 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
>              error_report("memory backend %s is used multiple times. Each "
>                           "-numa option must use a different memdev value.",
>                           path);
> +            g_free(path);
>              exit(1);
>          }
>  

Re: [Qemu-devel] [PATCH V5_resend 1/7] numa: Fixed the memory leak of numa error message

[Pankaj Gupta]

> 
> object_get_canonical_path_component() returns a string which
> must be freed using g_free().
> 
> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> ---
>  numa.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/numa.c b/numa.c
> index 50ec016..3875e1e 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -533,6 +533,7 @@ void memory_region_allocate_system_memory(MemoryRegion
> *mr, Object *owner,
>              error_report("memory backend %s is used multiple times. Each "
>                           "-numa option must use a different memdev value.",
>                           path);
> +            g_free(path);
>              exit(1);
>          }
>  
> --

Reviewed-by: Pankaj gupta <pagupta@redhat.com>

> 2.7.4

[Qemu-devel] [PATCH V5_resend 2/7] util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter

[Zhang Yi]

As more flag parameters besides the existing 'shared' are going to be
added to qemu_ram_mmap(), let's switch 'shared' to a 'flags' parameter
in advance, so as to ease the further additions.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
---
 exec.c                    |  3 +--
 include/qemu/mmap-alloc.h | 19 ++++++++++++++++++-
 util/mmap-alloc.c         |  8 +++++---
 util/oslib-posix.c        |  4 +++-
 4 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/exec.c b/exec.c
index bb6170d..273f668 100644
--- a/exec.c
+++ b/exec.c
@@ -1859,8 +1859,7 @@ static void *file_ram_alloc(RAMBlock *block,
         perror("ftruncate");
     }
 
-    area = qemu_ram_mmap(fd, memory, block->mr->align,
-                         block->flags & RAM_SHARED);
+    area = qemu_ram_mmap(fd, memory, block->mr->align, block->flags);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");
diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
index 50385e3..6fe6ed4 100644
--- a/include/qemu/mmap-alloc.h
+++ b/include/qemu/mmap-alloc.h
@@ -7,7 +7,24 @@ size_t qemu_fd_getpagesize(int fd);
 
 size_t qemu_mempath_getpagesize(const char *mem_path);
 
-void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared);
+/**
+ * qemu_ram_mmap: mmap the specified file or device.
+ *
+ * Parameters:
+ *  @fd: the file or the device to mmap
+ *  @size: the number of bytes to be mmaped
+ *  @align: if not zero, specify the alignment of the starting mapping address;
+ *          otherwise, the alignment in use will be determined by QEMU.
+ *  @flags: specifies additional properties of the mapping, which can be one or
+ *          bit-or of following values
+ *          - RAM_SHARED: mmap with MAP_SHARED flag
+ *          Other bits are ignored.
+ *
+ * Return:
+ *  On success, return a pointer to the mapped area.
+ *  On failure, return MAP_FAILED.
+ */
+void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags);
 
 void qemu_ram_munmap(void *ptr, size_t size);
 
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index fd329ec..8f0a740 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -13,6 +13,7 @@
 #include "qemu/osdep.h"
 #include "qemu/mmap-alloc.h"
 #include "qemu/host-utils.h"
+#include "exec/memory.h"
 
 #define HUGETLBFS_MAGIC       0x958458f6
 
@@ -75,7 +76,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
     return getpagesize();
 }
 
-void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
+void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags)
 {
     /*
      * Note: this always allocates at least one extra page of virtual address
@@ -92,11 +93,12 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
      * anonymous memory is OK.
      */
     int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;
-    int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
-    void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);
+    int mmap_flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
+    void *ptr = mmap(0, total, PROT_NONE, mmap_flags | MAP_PRIVATE, anonfd, 0);
 #else
     void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
 #endif
+    bool shared = flags & RAM_SHARED;
     size_t offset;
     void *ptr1;
 
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index fbd0dc8..c28869d 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -203,7 +203,9 @@ void *qemu_memalign(size_t alignment, size_t size)
 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
 {
     size_t align = QEMU_VMALLOC_ALIGN;
-    void *ptr = qemu_ram_mmap(-1, size, align, shared);
+    uint32_t flags = 0;
+    flags |= shared;
+    void *ptr = qemu_ram_mmap(-1, size, align, flags);
 
     if (ptr == MAP_FAILED) {
         return NULL;
-- 
2.7.4

[Qemu-devel] [PATCH V5_resend 3/7] exec: switch qemu_ram_alloc_from_{file, fd} to the 'flags' parameter

[Zhang Yi]

As more flag parameters besides the existing 'share' are going to be
added to qemu_ram_alloc_from_{file,fd}(), let's swith 'share' to a
'flags' parameters in advance, so as to ease the further additions.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
---
 exec.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/exec.c b/exec.c
index 273f668..e92a7da 100644
--- a/exec.c
+++ b/exec.c
@@ -1810,6 +1810,7 @@ static void *file_ram_alloc(RAMBlock *block,
                             ram_addr_t memory,
                             int fd,
                             bool truncate,
+                            uint32_t flags,
                             Error **errp)
 {
     void *area;
@@ -1859,7 +1860,7 @@ static void *file_ram_alloc(RAMBlock *block,
         perror("ftruncate");
     }
 
-    area = qemu_ram_mmap(fd, memory, block->mr->align, block->flags);
+    area = qemu_ram_mmap(fd, memory, block->mr->align, flags);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");
@@ -2278,7 +2279,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     new_block->used_length = size;
     new_block->max_length = size;
     new_block->flags = ram_flags;
-    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp);
+    new_block->host = file_ram_alloc(new_block, size, fd, !file_size,
+            ram_flags, errp);
     if (!new_block->host) {
         g_free(new_block);
         return NULL;
-- 
2.7.4

Re: [Qemu-devel] [PATCH V5_resend 3/7] exec: switch qemu_ram_alloc_from_{file, fd} to the 'flags' parameter

[Pankaj Gupta]

> 
> As more flag parameters besides the existing 'share' are going to be
> added to qemu_ram_alloc_from_{file,fd}(), let's swith 'share' to a
> 'flags' parameters in advance, so as to ease the further additions.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> ---
>  exec.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 273f668..e92a7da 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1810,6 +1810,7 @@ static void *file_ram_alloc(RAMBlock *block,
>                              ram_addr_t memory,
>                              int fd,
>                              bool truncate,
> +                            uint32_t flags,
>                              Error **errp)
>  {
>      void *area;
> @@ -1859,7 +1860,7 @@ static void *file_ram_alloc(RAMBlock *block,
>          perror("ftruncate");
>      }
>  
> -    area = qemu_ram_mmap(fd, memory, block->mr->align, block->flags);
> +    area = qemu_ram_mmap(fd, memory, block->mr->align, flags);

I think this change can be squashed with patch2 unless I am not missing 
anything here.

>      if (area == MAP_FAILED) {
>          error_setg_errno(errp, errno,
>                           "unable to map backing store for guest RAM");
> @@ -2278,7 +2279,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size,
> MemoryRegion *mr,
>      new_block->used_length = size;
>      new_block->max_length = size;
>      new_block->flags = ram_flags;
> -    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp);
> +    new_block->host = file_ram_alloc(new_block, size, fd, !file_size,
> +            ram_flags, errp);
>      if (!new_block->host) {
>          g_free(new_block);
>          return NULL;
> --
> 2.7.4
> 
> 
> 

Re: [Qemu-devel] [PATCH V5_resend 3/7] exec: switch qemu_ram_alloc_from_{file, fd} to the 'flags' parameter

[Yi Zhang]

On 2018-11-29 at 04:11:11 -0500, Pankaj Gupta wrote:
> 
> > 
> > As more flag parameters besides the existing 'share' are going to be
> > added to qemu_ram_alloc_from_{file,fd}(), let's swith 'share' to a
> > 'flags' parameters in advance, so as to ease the further additions.
> > 
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> > Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> > ---
> >  exec.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/exec.c b/exec.c
> > index 273f668..e92a7da 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -1810,6 +1810,7 @@ static void *file_ram_alloc(RAMBlock *block,
> >                              ram_addr_t memory,
> >                              int fd,
> >                              bool truncate,
> > +                            uint32_t flags,
> >                              Error **errp)
> >  {
> >      void *area;
> > @@ -1859,7 +1860,7 @@ static void *file_ram_alloc(RAMBlock *block,
> >          perror("ftruncate");
> >      }
> >  
> > -    area = qemu_ram_mmap(fd, memory, block->mr->align, block->flags);
> > +    area = qemu_ram_mmap(fd, memory, block->mr->align, flags);
> 
> I think this change can be squashed with patch2 unless I am not missing 
> anything here.

Yes, right, nothing just split the diffrent function in diffrent patch.
It's OK to squashed these 2 together. 
Thanks for the review. 

Yi.
> 
> >      if (area == MAP_FAILED) {
> >          error_setg_errno(errp, errno,
> >                           "unable to map backing store for guest RAM");
> > @@ -2278,7 +2279,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size,
> > MemoryRegion *mr,
> >      new_block->used_length = size;
> >      new_block->max_length = size;
> >      new_block->flags = ram_flags;
> > -    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp);
> > +    new_block->host = file_ram_alloc(new_block, size, fd, !file_size,
> > +            ram_flags, errp);
> >      if (!new_block->host) {
> >          g_free(new_block);
> >          return NULL;
> > --
> > 2.7.4
> > 
> > 
> > 

[Qemu-devel] [PATCH V5_resend 4/7] util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()

[Zhang Yi]

When a file supporting DAX is used as vNVDIMM backend, mmap it with
MAP_SYNC flag in addition can guarantee the persistence of guest write
to the backend file without other QEMU actions (e.g., periodic fsync()
by QEMU).

A set of RAM_SYNC flags are added to qemu_ram_mmap():

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
---
 exec.c                                |  2 +-
 include/exec/memory.h                 |  3 +++
 include/exec/ram_addr.h               |  1 +
 include/qemu/mmap-alloc.h             |  1 +
 include/standard-headers/linux/mman.h | 44 +++++++++++++++++++++++++++++++++++
 util/mmap-alloc.c                     | 14 +++++++----
 6 files changed, 60 insertions(+), 5 deletions(-)
 create mode 100644 include/standard-headers/linux/mman.h

diff --git a/exec.c b/exec.c
index e92a7da..dc4d180 100644
--- a/exec.c
+++ b/exec.c
@@ -2241,7 +2241,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     int64_t file_size;
 
     /* Just support these ram flags by now. */
-    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM)) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_SYNC)) == 0);
 
     if (xen_enabled()) {
         error_setg(errp, "-mem-path not supported with Xen");
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 667466b..33a4e2c 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -126,6 +126,9 @@ typedef struct IOMMUNotifier IOMMUNotifier;
 /* RAM is a persistent kind memory */
 #define RAM_PMEM (1 << 5)
 
+/* RAM can be mmap by a MAP_SYNC flag */
+#define RAM_SYNC (1 << 6)
+
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
                                        hwaddr start, hwaddr end,
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 9ecd911..d239ce7 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -87,6 +87,7 @@ long qemu_getrampagesize(void);
  *              or bit-or of following values
  *              - RAM_SHARED: mmap the backing file or device with MAP_SHARED
  *              - RAM_PMEM: the backend @mem_path or @fd is persistent memory
+ *              - RAM_SYNC:   mmap with MAP_SYNC flag
  *              Other bits are ignored.
  *  @mem_path or @fd: specify the backing file or device
  *  @errp: pointer to Error*, to store an error if it happens
diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
index 6fe6ed4..1755a8b 100644
--- a/include/qemu/mmap-alloc.h
+++ b/include/qemu/mmap-alloc.h
@@ -18,6 +18,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path);
  *  @flags: specifies additional properties of the mapping, which can be one or
  *          bit-or of following values
  *          - RAM_SHARED: mmap with MAP_SHARED flag
+ *          - RAM_SYNC:   mmap with MAP_SYNC flag
  *          Other bits are ignored.
  *
  * Return:
diff --git a/include/standard-headers/linux/mman.h b/include/standard-headers/linux/mman.h
new file mode 100644
index 0000000..ea1fc47
--- /dev/null
+++ b/include/standard-headers/linux/mman.h
@@ -0,0 +1,44 @@
+/*
+ * Definitions of Linux-specific mmap flags.
+ *
+ * Copyright Intel Corporation, 2018
+ *
+ * Author: Haozhong Zhang <haozhong.zhang@intel.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later. See the COPYING file in the top-level directory.
+ */
+
+#ifndef _LINUX_MMAN_H
+#define _LINUX_MMAN_H
+
+/*
+ * MAP_SHARED_VALIDATE and MAP_SYNC are introduced in Linux kernel
+ * 4.15, so they may not be defined when compiling on older kernels.
+ */
+#ifdef CONFIG_LINUX
+
+#include <sys/mman.h>
+
+#ifndef MAP_SHARED_VALIDATE
+#define MAP_SHARED_VALIDATE   0x3
+#endif
+
+#ifndef MAP_SYNC
+#define MAP_SYNC              0x80000
+#endif
+
+/* MAP_SYNC is only available with MAP_SHARED_VALIDATE. */
+#define MAP_SYNC_FLAGS (MAP_SYNC | MAP_SHARED_VALIDATE)
+
+#else  /* !CONFIG_LINUX */
+
+#define MAP_SHARED_VALIDATE   0x0
+#define MAP_SYNC              0x0
+
+#define QEMU_HAS_MAP_SYNC     false
+#define MAP_SYNC_FLAGS 0
+
+#endif /* CONFIG_LINUX */
+
+#endif /* !_LINUX_MMAN_H */
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 8f0a740..f411df7 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -14,6 +14,7 @@
 #include "qemu/mmap-alloc.h"
 #include "qemu/host-utils.h"
 #include "exec/memory.h"
+#include "standard-headers/linux/mman.h"
 
 #define HUGETLBFS_MAGIC       0x958458f6
 
@@ -99,6 +100,7 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags)
     void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
 #endif
     bool shared = flags & RAM_SHARED;
+    int mmap_xflags = 0;
     size_t offset;
     void *ptr1;
 
@@ -109,16 +111,20 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags)
     assert(is_power_of_2(align));
     /* Always align to host page size */
     assert(align >= getpagesize());
+    if ((flags & RAM_SYNC) && shared) {
+        mmap_xflags |= MAP_SYNC_FLAGS;
+    }
 
     offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
+ retry_mmap_fd:
     ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,
                 MAP_FIXED |
                 (fd == -1 ? MAP_ANONYMOUS : 0) |
-                (shared ? MAP_SHARED : MAP_PRIVATE),
+                (shared ? MAP_SHARED : MAP_PRIVATE) | mmap_xflags,
                 fd, 0);
-    if (ptr1 == MAP_FAILED) {
-        munmap(ptr, total);
-        return MAP_FAILED;
+    if ((ptr1 == MAP_FAILED) && (mmap_xflags & MAP_SYNC_FLAGS)) {
+        mmap_xflags &= ~MAP_SYNC_FLAGS;
+        goto retry_mmap_fd;
     }
 
     if (offset > 0) {
-- 
2.7.4

[Qemu-devel] [PATCH V5_resend 5/7] util/mmap-alloc: Switch the RAM_SYNC flags to OnOffAuto

[Zhang Yi]

Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>

A set of RAM_SYNC_ON_OFF_AUTO{AUTO,ON,OFF} flags are added to
qemu_ram_mmap():

- If RAM_SYNC_ON_OFF_AUTO_ON is present, qemu_ram_mmap() will try to pass
  MAP_SYNC to mmap(). It will then fail if the host OS or the backend
  file do not support MAP_SYNC, or MAP_SYNC is conflict with other
  flags.

- If RAM_SYNC_ON_OFF_AUTO_OFF is present, qemu_ram_mmap() will never pass
  MAP_SYNC to mmap().

- If RAM_SYNC_ON_OFF_AUTO_AUTO is present, and
  * if the host OS and the backend file support MAP_SYNC, and MAP_SYNC
    is not conflict with other flags, qemu_ram_mmap() will work as if
    RAM_SYNC_ON_OFF_AUTO_ON is present;
  * otherwise, qemu_ram_mmap() will work as if RAM_SYNC_ON_OFF_AUTO_OFF is
    present.
---
 include/exec/memory.h |  9 ++++++++-
 util/mmap-alloc.c     | 12 ++++++++++--
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 33a4e2c..c74c467 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -127,7 +127,14 @@ typedef struct IOMMUNotifier IOMMUNotifier;
 #define RAM_PMEM (1 << 5)
 
 /* RAM can be mmap by a MAP_SYNC flag */
-#define RAM_SYNC (1 << 6)
+#define RAM_SYNC_SHIFT  6
+#define RAM_SYNC_SHIFT_AUTO  7
+
+#define RAM_SYNC_ON_OFF_AUTO_ON   (1UL << RAM_SYNC_SHIFT)
+#define RAM_SYNC_ON_OFF_AUTO_OFF  (0UL << RAM_SYNC_SHIFT)
+#define RAM_SYNC_ON_OFF_AUTO_AUTO (1UL << RAM_SYNC_SHIFT_AUTO)
+
+#define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO)
 
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index f411df7..fe9303f 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -111,6 +111,10 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags)
     assert(is_power_of_2(align));
     /* Always align to host page size */
     assert(align >= getpagesize());
+    if ((flags & RAM_SYNC_ON_OFF_AUTO_ON) &&
+        (!shared || !MAP_SYNC_FLAGS)) {
+        return MAP_FAILED;
+    }
     if ((flags & RAM_SYNC) && shared) {
         mmap_xflags |= MAP_SYNC_FLAGS;
     }
@@ -123,8 +127,12 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags)
                 (shared ? MAP_SHARED : MAP_PRIVATE) | mmap_xflags,
                 fd, 0);
     if ((ptr1 == MAP_FAILED) && (mmap_xflags & MAP_SYNC_FLAGS)) {
-        mmap_xflags &= ~MAP_SYNC_FLAGS;
-        goto retry_mmap_fd;
+        if (flags & RAM_SYNC_ON_OFF_AUTO_AUTO) {
+            mmap_xflags &= ~MAP_SYNC_FLAGS;
+            goto retry_mmap_fd;
+        }
+        munmap(ptr, total);
+        return MAP_FAILED;
     }
 
     if (offset > 0) {
-- 
2.7.4

[Qemu-devel] [PATCH V5_resend 6/7] hostmem: add more information in error messages

[Zhang Yi]

When there are multiple memory backends in use, including the object type
name, ID and the property name in the error message can help users to
locate the error.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
---
 backends/hostmem-file.c | 6 ++++--
 backends/hostmem.c      | 8 +++++---
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index e640749..0dd7a90 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -82,7 +82,8 @@ static void set_mem_path(Object *o, const char *str, Error **errp)
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(errp, "cannot change property value");
+        error_setg(errp, "cannot change property 'mem-path' of %s",
+                   object_get_typename(o));
         return;
     }
     g_free(fb->mem_path);
@@ -120,7 +121,8 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
     uint64_t val;
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(&local_err, "cannot change property value");
+        error_setg(&local_err, "cannot change property '%s' of %s",
+                   name, object_get_typename(o));
         goto out;
     }
 
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 1a89342..e2bcf9f 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -47,7 +47,8 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
     uint64_t value;
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(&local_err, "cannot change property value");
+        error_setg(&local_err, "cannot change property %s of %s ",
+                   name, object_get_typename(obj));
         goto out;
     }
 
@@ -56,8 +57,9 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
         goto out;
     }
     if (!value) {
-        error_setg(&local_err, "Property '%s.%s' doesn't take value '%"
-                   PRIu64 "'", object_get_typename(obj), name, value);
+        error_setg(&local_err,
+                   "property '%s' of %s doesn't take value '%" PRIu64 "'",
+                   name, object_get_typename(obj), value);
         goto out;
     }
     backend->size = value;
-- 
2.7.4

[Qemu-devel] [PATCH V5_resend 7/7] hostmem-file: add 'sync' option

[Zhang Yi]

This option controls whether QEMU mmap(2) the memory backend file with
MAP_SYNC flag, which can fully guarantee the guest write persistence
to the backend, if MAP_SYNC flag is supported by the host kernel
(Linux kernel 4.15 and later) and the backend is a file supporting
DAX (e.g., file on ext4/xfs file system mounted with '-o dax').

It can take one of following values:
 - on:  try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
        'share=off', QEMU will abort
 - off: never pass MAP_SYNC to mmap(2)
 - auto (default): if MAP_SYNC is supported and 'share=on', work as if
        'sync=on'; otherwise, work as if 'sync=off'

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
---
 backends/hostmem-file.c | 39 +++++++++++++++++++++++++++++++++++++++
 docs/nvdimm.txt         | 20 +++++++++++++++++++-
 include/exec/memory.h   |  8 ++++++++
 qemu-options.hx         | 22 +++++++++++++++++++++-
 4 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 0dd7a90..73cf181 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -16,6 +16,7 @@
 #include "sysemu/hostmem.h"
 #include "sysemu/sysemu.h"
 #include "qom/object_interfaces.h"
+#include "qapi/qapi-visit.h"
 
 /* hostmem-file.c */
 /**
@@ -36,6 +37,7 @@ struct HostMemoryBackendFile {
     uint64_t align;
     bool discard_data;
     bool is_pmem;
+    OnOffAuto sync;
 };
 
 static void
@@ -62,6 +64,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
                                  path,
                                  backend->size, fb->align,
                                  (backend->share ? RAM_SHARED : 0) |
+                                 qemu_ram_sync_flags(fb->sync) |
                                  (fb->is_pmem ? RAM_PMEM : 0),
                                  fb->mem_path, errp);
         g_free(path);
@@ -136,6 +139,39 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
     error_propagate(errp, local_err);
 }
 
+static void file_memory_backend_get_sync(
+    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
+{
+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
+    OnOffAuto value = fb->sync;
+
+    visit_type_OnOffAuto(v, name, &value, errp);
+}
+
+static void file_memory_backend_set_sync(
+    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
+    Error *local_err = NULL;
+    OnOffAuto value;
+
+    if (host_memory_backend_mr_inited(backend)) {
+        error_setg(&local_err, "cannot change property '%s' of %s",
+                   name, object_get_typename(obj));
+        goto out;
+    }
+
+    visit_type_OnOffAuto(v, name, &value, &local_err);
+    if (local_err) {
+        goto out;
+    }
+    fb->sync = value;
+
+ out:
+    error_propagate(errp, local_err);
+}
+
 static bool file_memory_backend_get_pmem(Object *o, Error **errp)
 {
     return MEMORY_BACKEND_FILE(o)->is_pmem;
@@ -203,6 +239,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
     object_class_property_add_bool(oc, "pmem",
         file_memory_backend_get_pmem, file_memory_backend_set_pmem,
         &error_abort);
+    object_class_property_add(oc, "sync", "OnOffAuto",
+        file_memory_backend_get_sync, file_memory_backend_set_sync,
+        NULL, NULL, &error_abort);
 }
 
 static void file_backend_instance_finalize(Object *o)
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
index 5f158a6..3d89174 100644
--- a/docs/nvdimm.txt
+++ b/docs/nvdimm.txt
@@ -142,11 +142,29 @@ backend of vNVDIMM:
 Guest Data Persistence
 ----------------------
 
+vNVDIMM is designed and implemented to guarantee the guest data
+persistence on the backends even on the host crash and power
+failures. However, there are still some requirements and limitations
+as explained below.
+
 Though QEMU supports multiple types of vNVDIMM backends on Linux,
-currently the only one that can guarantee the guest write persistence
+if MAP_SYNC is not supported by the host kernel and the backends,
+the only backend that can guarantee the guest write persistence
 is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to
 which all guest access do not involve any host-side kernel cache.
 
+mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such
+systems, QEMU can mmap(2) the backend with MAP_SYNC, which can
+guarantee the guest write persistence to vNVDIMM. Besides the host
+kernel support, enabling MAP_SYNC in QEMU also requires:
+
+ - the backend is a file supporting DAX, e.g., a file on an ext4 or
+   xfs file system mounted with '-o dax',
+
+ - 'sync' option of memory-backend-file is not 'off', and
+
+ - 'share' option of memory-backend-file is 'on'.
+
 When using other types of backends, it's suggested to set 'unarmed'
 option of '-device nvdimm' to 'on', which sets the unarmed flag of the
 guest NVDIMM region mapping structure.  This unarmed flag indicates
diff --git a/include/exec/memory.h b/include/exec/memory.h
index c74c467..b398abb 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -26,6 +26,7 @@
 #include "qom/object.h"
 #include "qemu/rcu.h"
 #include "hw/qdev-core.h"
+#include "qapi/error.h"
 
 #define RAM_ADDR_INVALID (~(ram_addr_t)0)
 
@@ -136,6 +137,13 @@ typedef struct IOMMUNotifier IOMMUNotifier;
 
 #define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO)
 
+static inline uint64_t qemu_ram_sync_flags(OnOffAuto v)
+{
+    return v == ON_OFF_AUTO_OFF ? RAM_SYNC_ON_OFF_AUTO_OFF :
+           v == ON_OFF_AUTO_ON ? RAM_SYNC_ON_OFF_AUTO_ON :
+           RAM_SYNC_ON_OFF_AUTO_AUTO;
+}
+
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
                                        hwaddr start, hwaddr end,
diff --git a/qemu-options.hx b/qemu-options.hx
index 08f8516..77e8810 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3928,7 +3928,7 @@ property must be set.  These objects are placed in the
 
 @table @option
 
-@item -object memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align}
+@item -object memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto}
 
 Creates a memory file backend object, which can be used to back
 the guest RAM with huge pages.
@@ -4003,6 +4003,26 @@ If @option{pmem} is set to 'on', QEMU will take necessary operations to
 guarantee the persistence of its own writes to @option{mem-path}
 (e.g. in vNVDIMM label emulation and live migration).
 
+The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path}
+with MAP_SYNC flag, which can guarantee the guest write persistence to
+@option{mem-path} even on the host crash and power failures. MAP_SYNC
+requires supports from both the host kernel (since Linux kernel 4.15)
+and @option{mem-path} (only files supporting DAX). It can take one of
+following values:
+
+@table @option
+@item @var{on}
+try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
+@option{share}=@var{off}, QEMU will abort
+
+@item @var{off}
+never pass MAP_SYNC to mmap(2)
+
+@item @var{auto} (default)
+if MAP_SYNC is supported and @option{share}=@var{on}, work as if
+@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off}
+@end table
+
 @item -object memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@var{on|off},share=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave}
 
 Creates a memory backend object, which can be used to back the guest RAM.
-- 
2.7.4

Re: [Qemu-devel] [PATCH V5_resend 7/7] hostmem-file: add 'sync' option

[Pankaj Gupta]

> 
> This option controls whether QEMU mmap(2) the memory backend file with
> MAP_SYNC flag, which can fully guarantee the guest write persistence

Not sure 'persistence' is the right word here. I think it should be
something like 'consistent filesystem metadata for every guest write' just 
to avoid any confusion.

> to the backend, if MAP_SYNC flag is supported by the host kernel
> (Linux kernel 4.15 and later) and the backend is a file supporting
> DAX (e.g., file on ext4/xfs file system mounted with '-o dax').
> 
> It can take one of following values:
>  - on:  try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
>         'share=off', QEMU will abort
>  - off: never pass MAP_SYNC to mmap(2)
>  - auto (default): if MAP_SYNC is supported and 'share=on', work as if
>         'sync=on'; otherwise, work as if 'sync=off'
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> ---
>  backends/hostmem-file.c | 39 +++++++++++++++++++++++++++++++++++++++
>  docs/nvdimm.txt         | 20 +++++++++++++++++++-
>  include/exec/memory.h   |  8 ++++++++
>  qemu-options.hx         | 22 +++++++++++++++++++++-
>  4 files changed, 87 insertions(+), 2 deletions(-)
> 
> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> index 0dd7a90..73cf181 100644
> --- a/backends/hostmem-file.c
> +++ b/backends/hostmem-file.c
> @@ -16,6 +16,7 @@
>  #include "sysemu/hostmem.h"
>  #include "sysemu/sysemu.h"
>  #include "qom/object_interfaces.h"
> +#include "qapi/qapi-visit.h"
>  
>  /* hostmem-file.c */
>  /**
> @@ -36,6 +37,7 @@ struct HostMemoryBackendFile {
>      uint64_t align;
>      bool discard_data;
>      bool is_pmem;
> +    OnOffAuto sync;
>  };
>  
>  static void
> @@ -62,6 +64,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error
> **errp)
>                                   path,
>                                   backend->size, fb->align,
>                                   (backend->share ? RAM_SHARED : 0) |
> +                                 qemu_ram_sync_flags(fb->sync) |
>                                   (fb->is_pmem ? RAM_PMEM : 0),
>                                   fb->mem_path, errp);
>          g_free(path);
> @@ -136,6 +139,39 @@ static void file_memory_backend_set_align(Object *o,
> Visitor *v,
>      error_propagate(errp, local_err);
>  }
>  
> +static void file_memory_backend_get_sync(
> +    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
> +{
> +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
> +    OnOffAuto value = fb->sync;
> +
> +    visit_type_OnOffAuto(v, name, &value, errp);
> +}
> +
> +static void file_memory_backend_set_sync(
> +    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
> +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
> +    Error *local_err = NULL;
> +    OnOffAuto value;
> +
> +    if (host_memory_backend_mr_inited(backend)) {
> +        error_setg(&local_err, "cannot change property '%s' of %s",
> +                   name, object_get_typename(obj));
> +        goto out;
> +    }
> +
> +    visit_type_OnOffAuto(v, name, &value, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +    fb->sync = value;
> +
> + out:
> +    error_propagate(errp, local_err);
> +}
> +
>  static bool file_memory_backend_get_pmem(Object *o, Error **errp)
>  {
>      return MEMORY_BACKEND_FILE(o)->is_pmem;
> @@ -203,6 +239,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
>      object_class_property_add_bool(oc, "pmem",
>          file_memory_backend_get_pmem, file_memory_backend_set_pmem,
>          &error_abort);
> +    object_class_property_add(oc, "sync", "OnOffAuto",
> +        file_memory_backend_get_sync, file_memory_backend_set_sync,
> +        NULL, NULL, &error_abort);
>  }
>  
>  static void file_backend_instance_finalize(Object *o)
> diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
> index 5f158a6..3d89174 100644
> --- a/docs/nvdimm.txt
> +++ b/docs/nvdimm.txt
> @@ -142,11 +142,29 @@ backend of vNVDIMM:
>  Guest Data Persistence
>  ----------------------
>  
> +vNVDIMM is designed and implemented to guarantee the guest data
> +persistence on the backends even on the host crash and power
> +failures. However, there are still some requirements and limitations
> +as explained below.
> +
>  Though QEMU supports multiple types of vNVDIMM backends on Linux,
> -currently the only one that can guarantee the guest write persistence
> +if MAP_SYNC is not supported by the host kernel and the backends,
> +the only backend that can guarantee the guest write persistence
>  is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to
>  which all guest access do not involve any host-side kernel cache.
>  
> +mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such
> +systems, QEMU can mmap(2) the backend with MAP_SYNC, which can

I think its important to clear about the type of backend. 
i.e DAX file on real NVDIMM device backend.

Thanks,
Pankaj 

> +guarantee the guest write persistence to vNVDIMM. Besides the host
> +kernel support, enabling MAP_SYNC in QEMU also requires:
> +
> + - the backend is a file supporting DAX, e.g., a file on an ext4 or
> +   xfs file system mounted with '-o dax',
> +
> + - 'sync' option of memory-backend-file is not 'off', and
> +
> + - 'share' option of memory-backend-file is 'on'.
> +
>  When using other types of backends, it's suggested to set 'unarmed'
>  option of '-device nvdimm' to 'on', which sets the unarmed flag of the
>  guest NVDIMM region mapping structure.  This unarmed flag indicates
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index c74c467..b398abb 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -26,6 +26,7 @@
>  #include "qom/object.h"
>  #include "qemu/rcu.h"
>  #include "hw/qdev-core.h"
> +#include "qapi/error.h"
>  
>  #define RAM_ADDR_INVALID (~(ram_addr_t)0)
>  
> @@ -136,6 +137,13 @@ typedef struct IOMMUNotifier IOMMUNotifier;
>  
>  #define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO)
>  
> +static inline uint64_t qemu_ram_sync_flags(OnOffAuto v)
> +{
> +    return v == ON_OFF_AUTO_OFF ? RAM_SYNC_ON_OFF_AUTO_OFF :
> +           v == ON_OFF_AUTO_ON ? RAM_SYNC_ON_OFF_AUTO_ON :
> +           RAM_SYNC_ON_OFF_AUTO_AUTO;
> +}
> +
>  static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
>                                         IOMMUNotifierFlag flags,
>                                         hwaddr start, hwaddr end,
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 08f8516..77e8810 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3928,7 +3928,7 @@ property must be set.  These objects are placed in the
>  
>  @table @option
>  
> -@item -object
> memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align}
> +@item -object
> memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto}
>  
>  Creates a memory file backend object, which can be used to back
>  the guest RAM with huge pages.
> @@ -4003,6 +4003,26 @@ If @option{pmem} is set to 'on', QEMU will take
> necessary operations to
>  guarantee the persistence of its own writes to @option{mem-path}
>  (e.g. in vNVDIMM label emulation and live migration).
>  
> +The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path}
> +with MAP_SYNC flag, which can guarantee the guest write persistence to
> +@option{mem-path} even on the host crash and power failures. MAP_SYNC
> +requires supports from both the host kernel (since Linux kernel 4.15)
> +and @option{mem-path} (only files supporting DAX). It can take one of
> +following values:
> +
> +@table @option
> +@item @var{on}
> +try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
> +@option{share}=@var{off}, QEMU will abort
> +
> +@item @var{off}
> +never pass MAP_SYNC to mmap(2)
> +
> +@item @var{auto} (default)
> +if MAP_SYNC is supported and @option{share}=@var{on}, work as if
> +@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off}
> +@end table
> +
>  @item -object
>  memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@var{on|off},share=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave}
>  
>  Creates a memory backend object, which can be used to back the guest RAM.
> --
> 2.7.4
> 
> 
> 

Re: [Qemu-devel] [PATCH V5_resend 7/7] hostmem-file: add 'sync' option

[Yi Zhang]

On 2018-11-26 at 03:46:50 -0500, Pankaj Gupta wrote:
> 
> > 
> > This option controls whether QEMU mmap(2) the memory backend file with
> > MAP_SYNC flag, which can fully guarantee the guest write persistence
> 
> Not sure 'persistence' is the right word here. I think it should be
> something like 'consistent filesystem metadata for every guest write' just 
> to avoid any confusion.

Yes, Agree, the main porpurse of this flag is "*consistent filesystem
metadata", I will improve that comments in next version

Regards
Yi.

> 
> > to the backend, if MAP_SYNC flag is supported by the host kernel
> > (Linux kernel 4.15 and later) and the backend is a file supporting
> > DAX (e.g., file on ext4/xfs file system mounted with '-o dax').
> > 
> > It can take one of following values:
> >  - on:  try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
> >         'share=off', QEMU will abort
> >  - off: never pass MAP_SYNC to mmap(2)
> >  - auto (default): if MAP_SYNC is supported and 'share=on', work as if
> >         'sync=on'; otherwise, work as if 'sync=off'
> > 
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> > Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> > ---
> >  backends/hostmem-file.c | 39 +++++++++++++++++++++++++++++++++++++++
> >  docs/nvdimm.txt         | 20 +++++++++++++++++++-
> >  include/exec/memory.h   |  8 ++++++++
> >  qemu-options.hx         | 22 +++++++++++++++++++++-
> >  4 files changed, 87 insertions(+), 2 deletions(-)
> > 
> > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> > index 0dd7a90..73cf181 100644
> > --- a/backends/hostmem-file.c
> > +++ b/backends/hostmem-file.c
> > @@ -16,6 +16,7 @@
> >  #include "sysemu/hostmem.h"
> >  #include "sysemu/sysemu.h"
> >  #include "qom/object_interfaces.h"
> > +#include "qapi/qapi-visit.h"
> >  
> >  /* hostmem-file.c */
> >  /**
> > @@ -36,6 +37,7 @@ struct HostMemoryBackendFile {
> >      uint64_t align;
> >      bool discard_data;
> >      bool is_pmem;
> > +    OnOffAuto sync;
> >  };
> >  
> >  static void
> > @@ -62,6 +64,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error
> > **errp)
> >                                   path,
> >                                   backend->size, fb->align,
> >                                   (backend->share ? RAM_SHARED : 0) |
> > +                                 qemu_ram_sync_flags(fb->sync) |
> >                                   (fb->is_pmem ? RAM_PMEM : 0),
> >                                   fb->mem_path, errp);
> >          g_free(path);
> > @@ -136,6 +139,39 @@ static void file_memory_backend_set_align(Object *o,
> > Visitor *v,
> >      error_propagate(errp, local_err);
> >  }
> >  
> > +static void file_memory_backend_get_sync(
> > +    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
> > +{
> > +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
> > +    OnOffAuto value = fb->sync;
> > +
> > +    visit_type_OnOffAuto(v, name, &value, errp);
> > +}
> > +
> > +static void file_memory_backend_set_sync(
> > +    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
> > +{
> > +    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
> > +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
> > +    Error *local_err = NULL;
> > +    OnOffAuto value;
> > +
> > +    if (host_memory_backend_mr_inited(backend)) {
> > +        error_setg(&local_err, "cannot change property '%s' of %s",
> > +                   name, object_get_typename(obj));
> > +        goto out;
> > +    }
> > +
> > +    visit_type_OnOffAuto(v, name, &value, &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +    fb->sync = value;
> > +
> > + out:
> > +    error_propagate(errp, local_err);
> > +}
> > +
> >  static bool file_memory_backend_get_pmem(Object *o, Error **errp)
> >  {
> >      return MEMORY_BACKEND_FILE(o)->is_pmem;
> > @@ -203,6 +239,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
> >      object_class_property_add_bool(oc, "pmem",
> >          file_memory_backend_get_pmem, file_memory_backend_set_pmem,
> >          &error_abort);
> > +    object_class_property_add(oc, "sync", "OnOffAuto",
> > +        file_memory_backend_get_sync, file_memory_backend_set_sync,
> > +        NULL, NULL, &error_abort);
> >  }
> >  
> >  static void file_backend_instance_finalize(Object *o)
> > diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
> > index 5f158a6..3d89174 100644
> > --- a/docs/nvdimm.txt
> > +++ b/docs/nvdimm.txt
> > @@ -142,11 +142,29 @@ backend of vNVDIMM:
> >  Guest Data Persistence
> >  ----------------------
> >  
> > +vNVDIMM is designed and implemented to guarantee the guest data
> > +persistence on the backends even on the host crash and power
> > +failures. However, there are still some requirements and limitations
> > +as explained below.
> > +
> >  Though QEMU supports multiple types of vNVDIMM backends on Linux,
> > -currently the only one that can guarantee the guest write persistence
> > +if MAP_SYNC is not supported by the host kernel and the backends,
> > +the only backend that can guarantee the guest write persistence
> >  is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to
> >  which all guest access do not involve any host-side kernel cache.
> >  
> > +mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such
> > +systems, QEMU can mmap(2) the backend with MAP_SYNC, which can
> 
> I think its important to clear about the type of backend. 
> i.e DAX file on real NVDIMM device backend.
> 
> Thanks,
> Pankaj 
> 
> > +guarantee the guest write persistence to vNVDIMM. Besides the host
> > +kernel support, enabling MAP_SYNC in QEMU also requires:
> > +
> > + - the backend is a file supporting DAX, e.g., a file on an ext4 or
> > +   xfs file system mounted with '-o dax',
> > +
> > + - 'sync' option of memory-backend-file is not 'off', and
> > +
> > + - 'share' option of memory-backend-file is 'on'.
> > +
> >  When using other types of backends, it's suggested to set 'unarmed'
> >  option of '-device nvdimm' to 'on', which sets the unarmed flag of the
> >  guest NVDIMM region mapping structure.  This unarmed flag indicates
> > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > index c74c467..b398abb 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -26,6 +26,7 @@
> >  #include "qom/object.h"
> >  #include "qemu/rcu.h"
> >  #include "hw/qdev-core.h"
> > +#include "qapi/error.h"
> >  
> >  #define RAM_ADDR_INVALID (~(ram_addr_t)0)
> >  
> > @@ -136,6 +137,13 @@ typedef struct IOMMUNotifier IOMMUNotifier;
> >  
> >  #define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO)
> >  
> > +static inline uint64_t qemu_ram_sync_flags(OnOffAuto v)
> > +{
> > +    return v == ON_OFF_AUTO_OFF ? RAM_SYNC_ON_OFF_AUTO_OFF :
> > +           v == ON_OFF_AUTO_ON ? RAM_SYNC_ON_OFF_AUTO_ON :
> > +           RAM_SYNC_ON_OFF_AUTO_AUTO;
> > +}
> > +
> >  static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
> >                                         IOMMUNotifierFlag flags,
> >                                         hwaddr start, hwaddr end,
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 08f8516..77e8810 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -3928,7 +3928,7 @@ property must be set.  These objects are placed in the
> >  
> >  @table @option
> >  
> > -@item -object
> > memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align}
> > +@item -object
> > memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto}
> >  
> >  Creates a memory file backend object, which can be used to back
> >  the guest RAM with huge pages.
> > @@ -4003,6 +4003,26 @@ If @option{pmem} is set to 'on', QEMU will take
> > necessary operations to
> >  guarantee the persistence of its own writes to @option{mem-path}
> >  (e.g. in vNVDIMM label emulation and live migration).
> >  
> > +The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path}
> > +with MAP_SYNC flag, which can guarantee the guest write persistence to
> > +@option{mem-path} even on the host crash and power failures. MAP_SYNC
> > +requires supports from both the host kernel (since Linux kernel 4.15)
> > +and @option{mem-path} (only files supporting DAX). It can take one of
> > +following values:
> > +
> > +@table @option
> > +@item @var{on}
> > +try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
> > +@option{share}=@var{off}, QEMU will abort
> > +
> > +@item @var{off}
> > +never pass MAP_SYNC to mmap(2)
> > +
> > +@item @var{auto} (default)
> > +if MAP_SYNC is supported and @option{share}=@var{on}, work as if
> > +@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off}
> > +@end table
> > +
> >  @item -object
> >  memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@var{on|off},share=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave}
> >  
> >  Creates a memory backend object, which can be used to back the guest RAM.
> > --
> > 2.7.4
> > 
> > 
> > 

Re: [Qemu-devel] [PATCH V5_resend 0/7] nvdimm: support MAP_SYNC for memory-backend-file

[Yi Zhang]

Ping for any review/comments 
Thanks
Yi

On 2018-11-20 at 15:47:58 +0800, Zhang Yi wrote:
> Linux 4.15 introduces a new mmap flag MAP_SYNC, which can be used to
> guarantee the write persistence to mmap'ed files supporting DAX (e.g.,
> files on ext4/xfs file system mounted with '-o dax').
> 
> A description of MAP_SYNC and MAP_SHARED_VALIDATE can be found at
>     https://patchwork.kernel.org/patch/10028151/
> 
> In order to make sure that the file metadata is in sync after a fault 
> while we are writing a shared DAX supporting backend files, this
> patch-set enables QEMU to use MAP_SYNC flag for memory-backend-dax-file.
> 
> As the DAX vs DMA truncated issue was solved, we refined the code and
> send out this feature for the v5 version.
> 
> A new auto on/off option 'sync' is added to memory-backend-file:
>  - on:  try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
>         'share=off', QEMU will abort
>  - off: never pass MAP_SYNC to mmap(2)
>  - auto (default): if MAP_SYNC is supported and 'share=on', work as if
>         'sync=on'; otherwise, work as if 'sync=off'

Changes in v5:
 * Add patch 1 to fix a memory leak issue.
 * Refine the patch 4-6
 * Remove the patch 3 as we already change the parameter from "shared" to
   "flags"

Changes in v4:
 * Add patch 1-3 to switch some functions to a single 'flags'
   parameters. (Michael S. Tsirkin)
 * v3 patch 1-3 become v4 patch 4-6.
 * Patch 4: move definitions of MAP_SYNC and MAP_SHARED_VALIDATE to a
   new header file under include/standard-headers/linux/. (Michael S. Tsirkin)
 * Patch 6: refine the description of the 'sync' option. (Michael S. Tsirkin)

Changes in v3:
 * Patch 1: add MAP_SHARED_VALIDATE in both sync=on and sync=auto
   cases, and add back the retry mechanism. MAP_SYNC will be ignored
   by Linux kernel 4.15 if MAP_SHARED_VALIDATE is missed.
 * Patch 1: define MAP_SYNC and MAP_SHARED_VALIDATE as 0 on non-Linux
   platforms in order to make qemu_ram_mmap() compile on those platforms.
 * Patch 2&3: include more information in error messages of
   memory-backend in hope to help user to identify the error.
   (Dr. David Alan Gilbert)
 * Patch 3: fix typo in the commit message. (Dr. David Alan Gilbert)

Changes in v2:
 * Add 'sync' option to control the use of MAP_SYNC. (Eduardo Habkost)
 * Remove the unnecessary set of MAP_SHARED_VALIDATE in some cases and
   the retry mechanism in qemu_ram_mmap(). (Michael S. Tsirkin)
 * Move OS dependent definitions of MAP_SYNC and MAP_SHARED_VALIDATE
   to osdep.h. (Michael S. Tsirkin)
> 
> Zhang Yi (7):
>   numa: Fixed the memory leak of numa error message
>   util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter
>   exec: switch qemu_ram_alloc_from_{file, fd} to the 'flags' parameter
>   util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
>   util/mmap-alloc: Switch the RAM_SYNC flags to OnOffAuto
>   hostmem: add more information in error messages
>   hostmem-file: add 'sync' option
> 
>  backends/hostmem-file.c               | 45 +++++++++++++++++++++++++++++++++--
>  backends/hostmem.c                    |  8 ++++---
>  docs/nvdimm.txt                       | 20 +++++++++++++++-
>  exec.c                                |  9 +++----
>  include/exec/memory.h                 | 18 ++++++++++++++
>  include/exec/ram_addr.h               |  1 +
>  include/qemu/mmap-alloc.h             | 20 +++++++++++++++-
>  include/standard-headers/linux/mman.h | 44 ++++++++++++++++++++++++++++++++++
>  numa.c                                |  1 +
>  qemu-options.hx                       | 22 ++++++++++++++++-
>  util/mmap-alloc.c                     | 26 ++++++++++++++++----
>  util/oslib-posix.c                    |  4 +++-
>  12 files changed, 200 insertions(+), 18 deletions(-)
>  create mode 100644 include/standard-headers/linux/mman.h
> 
> -- 
> 2.7.4
>