Re: [Qemu-devel] [PATCH v3 1/3] util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()

2018-01-24 Thread Haozhong Zhang 
On 01/24/18 22:20 +0200, Michael S. Tsirkin wrote:
> > index 50385e3f81..dd5876471f 100644
> > --- a/include/qemu/mmap-alloc.h
> > +++ b/include/qemu/mmap-alloc.h
> > @@ -7,7 +7,8 @@ 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);
> > +void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared,
> > +OnOffAuto sync);
> >  
> >  void qemu_ram_munmap(void *ptr, size_t size);
> >  
> 
> And Marcel plans to add a remappable flag ...  Is it time we
> switched to a flags field?

Yes. Some patches on my hands are going to add another field to this
function, so let's switch to flags.

> 
> > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> > index adb3758275..0ff10cb529 100644
> > --- a/include/qemu/osdep.h
> > +++ b/include/qemu/osdep.h
> > @@ -372,6 +372,24 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> >  #  define QEMU_VMALLOC_ALIGN getpagesize()
> >  #endif
> >  
> > +/*
> > + * MAP_SHARED_VALIDATE and MAP_SYNC were introduced in Linux kernel
> > + * 4.15, so they may not be defined when compiling on older kernels.
> > + */
> > +#ifdef CONFIG_LINUX
> > +#ifndef MAP_SHARED_VALIDATE
> > +#define MAP_SHARED_VALIDATE   0x3
> > +#endif
> > +#ifndef MAP_SYNC
> > +#define MAP_SYNC  0x8
> > +#endif
> > +#define QEMU_HAS_MAP_SYNC true
> > +#else  /* !CONFIG_LINUX */
> > +#define MAP_SHARED_VALIDATE   0x0
> > +#define MAP_SYNC  0x0
> > +#define QEMU_HAS_MAP_SYNC false
> > +#endif /* CONFIG_LINUX */
> > +
> >  #ifdef CONFIG_POSIX
> >  struct qemu_signalfd_siginfo {
> >  uint32_t ssi_signo;   /* Signal number */
> 
> Please just import this into standard-headers from Linux.
>

Sure, I'll move it to a new file include/standard-headers/linux/mman.h.

Thanks,
Haozhong

Re: [Qemu-devel] [PATCH v3 1/3] util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()

2018-01-24 Thread Michael S. Tsirkin 
> index 50385e3f81..dd5876471f 100644
> --- a/include/qemu/mmap-alloc.h
> +++ b/include/qemu/mmap-alloc.h
> @@ -7,7 +7,8 @@ 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);
> +void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared,
> +OnOffAuto sync);
>  
>  void qemu_ram_munmap(void *ptr, size_t size);
>  

And Marcel plans to add a remappable flag ...  Is it time we
switched to a flags field?

> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index adb3758275..0ff10cb529 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -372,6 +372,24 @@ void qemu_anon_ram_free(void *ptr, size_t size);
>  #  define QEMU_VMALLOC_ALIGN getpagesize()
>  #endif
>  
> +/*
> + * MAP_SHARED_VALIDATE and MAP_SYNC were introduced in Linux kernel
> + * 4.15, so they may not be defined when compiling on older kernels.
> + */
> +#ifdef CONFIG_LINUX
> +#ifndef MAP_SHARED_VALIDATE
> +#define MAP_SHARED_VALIDATE   0x3
> +#endif
> +#ifndef MAP_SYNC
> +#define MAP_SYNC  0x8
> +#endif
> +#define QEMU_HAS_MAP_SYNC true
> +#else  /* !CONFIG_LINUX */
> +#define MAP_SHARED_VALIDATE   0x0
> +#define MAP_SYNC  0x0
> +#define QEMU_HAS_MAP_SYNC false
> +#endif /* CONFIG_LINUX */
> +
>  #ifdef CONFIG_POSIX
>  struct qemu_signalfd_siginfo {
>  uint32_t ssi_signo;   /* Signal number */

Please just import this into standard-headers from Linux.

[Qemu-devel] [PATCH v3 1/3] util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()

2018-01-17 Thread Haozhong Zhang 
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 OnOffAuto parameter 'sync' is added to qemu_ram_mmap():

- If sync == ON_OFF_AUTO_ON, 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 sync == ON_OFF_AUTO_OFF, qemu_ram_mmap() will never pass MAP_SYNC
  to mmap().

- If sync == ON_OFF_AUTO_AUTO, 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
sync == ON_OFF_AUTO_ON.
  * otherwise, qemu_ram_mmap() will work as if sync == ON_OFF_AUTO_OFF.

Signed-off-by: Haozhong Zhang 
---
 exec.c|  2 +-
 include/qemu/mmap-alloc.h |  3 ++-
 include/qemu/osdep.h  | 18 ++
 util/mmap-alloc.c | 24 ++--
 util/oslib-posix.c|  2 +-
 5 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/exec.c b/exec.c
index 8fba88ae1c..f4254cb6d3 100644
--- a/exec.c
+++ b/exec.c
@@ -1646,7 +1646,7 @@ static void *file_ram_alloc(RAMBlock *block,
 }
 
 area = qemu_ram_mmap(fd, memory, block->mr->align,
- block->flags & RAM_SHARED);
+ block->flags & RAM_SHARED, ON_OFF_AUTO_OFF);
 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 50385e3f81..dd5876471f 100644
--- a/include/qemu/mmap-alloc.h
+++ b/include/qemu/mmap-alloc.h
@@ -7,7 +7,8 @@ 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);
+void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared,
+OnOffAuto sync);
 
 void qemu_ram_munmap(void *ptr, size_t size);
 
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index adb3758275..0ff10cb529 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -372,6 +372,24 @@ void qemu_anon_ram_free(void *ptr, size_t size);
 #  define QEMU_VMALLOC_ALIGN getpagesize()
 #endif
 
+/*
+ * MAP_SHARED_VALIDATE and MAP_SYNC were introduced in Linux kernel
+ * 4.15, so they may not be defined when compiling on older kernels.
+ */
+#ifdef CONFIG_LINUX
+#ifndef MAP_SHARED_VALIDATE
+#define MAP_SHARED_VALIDATE   0x3
+#endif
+#ifndef MAP_SYNC
+#define MAP_SYNC  0x8
+#endif
+#define QEMU_HAS_MAP_SYNC true
+#else  /* !CONFIG_LINUX */
+#define MAP_SHARED_VALIDATE   0x0
+#define MAP_SYNC  0x0
+#define QEMU_HAS_MAP_SYNC false
+#endif /* CONFIG_LINUX */
+
 #ifdef CONFIG_POSIX
 struct qemu_signalfd_siginfo {
 uint32_t ssi_signo;   /* Signal number */
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 2fd8cbcc6f..b42d9719f3 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -73,7 +73,8 @@ 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, bool shared,
+OnOffAuto sync)
 {
 /*
  * Note: this always allocates at least one extra page of virtual address
@@ -97,6 +98,7 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool 
shared)
 #endif
 size_t offset;
 void *ptr1;
+int xflags = 0;
 
 if (ptr == MAP_FAILED) {
 return MAP_FAILED;
@@ -106,13 +108,31 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, 
bool shared)
 /* Always align to host page size */
 assert(align >= getpagesize());
 
+if (!QEMU_HAS_MAP_SYNC || !shared) {
+if (sync == ON_OFF_AUTO_ON) {
+return MAP_FAILED;
+}
+sync = ON_OFF_AUTO_OFF;
+}
+if (sync != ON_OFF_AUTO_OFF) {
+/* MAP_SYNC is only available with MAP_SHARED_VALIDATE. */
+xflags |= MAP_SYNC | MAP_SHARED_VALIDATE;
+}
+
 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) | xflags,
 fd, 0);
 if (ptr1 == MAP_FAILED) {
+if (sync == ON_OFF_AUTO_AUTO) {
+xflags &= ~(MAP_SYNC | MAP_SHARED_VALIDATE);
+sync = ON_OFF_AUTO_OFF;
+goto retry_mmap_fd;
+}
+
 munmap(ptr, total);
 return MAP_FAILED;
 }
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 77369c92ce..ecb1c275d2