diff mbox series

[V7,2/6] util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter

Message ID 62a8796330b86f9f6571e48755d718db11855a6b.1545120100.git.yi.z.zhang@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series nvdimm: support MAP_SYNC for memory-backend-file | expand

Commit Message

Zhang, Yi Dec. 18, 2018, 8:17 a.m. UTC 
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                    |  7 ++++---
 include/qemu/mmap-alloc.h | 19 ++++++++++++++++++-
 util/mmap-alloc.c         |  8 +++++---
 util/oslib-posix.c        |  8 +++++++-
 4 files changed, 34 insertions(+), 8 deletions(-)

Comments

Michael S. Tsirkin Dec. 18, 2018, 1:35 p.m. UTC | #1 
On Tue, Dec 18, 2018 at 04:17:04PM +0800, Zhang Yi wrote:
> 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>

And that's the trouble with patch 1: no type safety.
See below

> ---
>  exec.c                    |  7 ++++---
>  include/qemu/mmap-alloc.h | 19 ++++++++++++++++++-
>  util/mmap-alloc.c         |  8 +++++---
>  util/oslib-posix.c        |  8 +++++++-
>  4 files changed, 34 insertions(+), 8 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index bb6170d..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;
> @@ -1859,8 +1860,7 @@ 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, flags);
>      if (area == MAP_FAILED) {
>          error_setg_errno(errp, errno,
>                           "unable to map backing store for guest RAM");
> @@ -2279,7 +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;
> 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.
> + *

So set it to RAM_SHARED to require a shared mapping ...

> + * 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..121c31f 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -203,7 +203,13 @@ 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;
> +    void *ptr;
> +
> +    if (shared) {
> +        flags = MAP_SHARED;
> +    }

And here we set it to MAP_SHARED instead.
Not good - was this even tested?

> +    ptr = qemu_ram_mmap(-1, size, align, flags);
>  
>      if (ptr == MAP_FAILED) {
>          return NULL;
> -- 
> 2.7.4


Suggestion:

#ifdef __CHECKER__
#define QEMU_BITWISE __attribute__((bitwise))
#define QEMU_FORCE   __attribute__((force))
#else
#define QEMU_BITWISE
#define QEMU_FORCE
#endif

typedef unsigned QEMU_BITWISE QemuMmapFlags;

#define RAM_SHARED ((QEMU_FORCE QemuMmapFlags) (1 << 1))

And then run checker to detect misuse.
diff mbox series

Patch

diff --git a/exec.c b/exec.c
index bb6170d..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;
@@ -1859,8 +1860,7 @@  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, flags);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");
@@ -2279,7 +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;
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..121c31f 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -203,7 +203,13 @@  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;
+    void *ptr;
+
+    if (shared) {
+        flags = MAP_SHARED;
+    }
+    ptr = qemu_ram_mmap(-1, size, align, flags);
 
     if (ptr == MAP_FAILED) {
         return NULL;