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Re: [PATCH v4 07/15] util/mmap-alloc: Factor out calculation of the page
From: |
Murilo Opsfelder Araújo |
Subject: |
Re: [PATCH v4 07/15] util/mmap-alloc: Factor out calculation of the pagesize for the guard page |
Date: |
Wed, 25 Mar 2020 12:03:55 -0300 |
On Thursday, March 5, 2020 11:29:37 AM -03 David Hildenbrand wrote:
> Let's factor out calculating the size of the guard page and rename the
> variable to make it clearer that this pagesize only applies to the
> guard page.
>
> Reviewed-by: Peter Xu <address@hidden>
> Cc: "Michael S. Tsirkin" <address@hidden>
> Cc: Murilo Opsfelder Araujo <address@hidden>
> Cc: Greg Kurz <address@hidden>
> Cc: Eduardo Habkost <address@hidden>
> Cc: "Dr. David Alan Gilbert" <address@hidden>
> Cc: Igor Mammedov <address@hidden>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
Acked-by: Murilo Opsfelder Araujo <address@hidden>
> util/mmap-alloc.c | 31 ++++++++++++++++---------------
> 1 file changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> index 27dcccd8ec..f0277f9fad 100644
> --- a/util/mmap-alloc.c
> +++ b/util/mmap-alloc.c
> @@ -82,17 +82,27 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
> return qemu_real_host_page_size;
> }
>
> +static inline size_t mmap_guard_pagesize(int fd)
> +{
> +#if defined(__powerpc64__) && defined(__linux__)
> + /* Mappings in the same segment must share the same page size */
> + return qemu_fd_getpagesize(fd);
> +#else
> + return qemu_real_host_page_size;
> +#endif
> +}
> +
> void *qemu_ram_mmap(int fd,
> size_t size,
> size_t align,
> bool shared,
> bool is_pmem)
> {
> + const size_t guard_pagesize = mmap_guard_pagesize(fd);
> int flags;
> int map_sync_flags = 0;
> int guardfd;
> size_t offset;
> - size_t pagesize;
> size_t total;
> void *guardptr;
> void *ptr;
> @@ -113,8 +123,7 @@ void *qemu_ram_mmap(int fd,
> * anonymous memory is OK.
> */
> flags = MAP_PRIVATE;
> - pagesize = qemu_fd_getpagesize(fd);
> - if (fd == -1 || pagesize == qemu_real_host_page_size) {
> + if (fd == -1 || guard_pagesize == qemu_real_host_page_size) {
> guardfd = -1;
> flags |= MAP_ANONYMOUS;
> } else {
> @@ -123,7 +132,6 @@ void *qemu_ram_mmap(int fd,
> }
> #else
> guardfd = -1;
> - pagesize = qemu_real_host_page_size;
> flags = MAP_PRIVATE | MAP_ANONYMOUS;
> #endif
>
> @@ -135,7 +143,7 @@ void *qemu_ram_mmap(int fd,
>
> assert(is_power_of_2(align));
> /* Always align to host page size */
> - assert(align >= pagesize);
> + assert(align >= guard_pagesize);
>
> flags = MAP_FIXED;
> flags |= fd == -1 ? MAP_ANONYMOUS : 0;
> @@ -189,8 +197,8 @@ void *qemu_ram_mmap(int fd,
> * a guard page guarding against potential buffer overflows.
> */
> total -= offset;
> - if (total > size + pagesize) {
> - munmap(ptr + size + pagesize, total - size - pagesize);
> + if (total > size + guard_pagesize) {
> + munmap(ptr + size + guard_pagesize, total - size - guard_pagesize);
> }
>
> return ptr;
> @@ -198,15 +206,8 @@ void *qemu_ram_mmap(int fd,
>
> void qemu_ram_munmap(int fd, void *ptr, size_t size)
> {
> - size_t pagesize;
> -
> if (ptr) {
> /* Unmap both the RAM block and the guard page */
> -#if defined(__powerpc64__) && defined(__linux__)
> - pagesize = qemu_fd_getpagesize(fd);
> -#else
> - pagesize = qemu_real_host_page_size;
> -#endif
> - munmap(ptr, size + pagesize);
> + munmap(ptr, size + mmap_guard_pagesize(fd));
> }
> }
--
Murilo
- [PATCH v4 05/15] exec: Reuse qemu_ram_apply_settings() in qemu_ram_remap(), (continued)
- [PATCH v4 05/15] exec: Reuse qemu_ram_apply_settings() in qemu_ram_remap(), David Hildenbrand, 2020/03/05
- [PATCH v4 04/15] exec: Factor out setting ram settings (madvise ...) into qemu_ram_apply_settings(), David Hildenbrand, 2020/03/05
- [PATCH v4 08/15] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve(), David Hildenbrand, 2020/03/05
- [PATCH v4 06/15] exec: Drop "shared" parameter from ram_block_add(), David Hildenbrand, 2020/03/05
- [PATCH v4 09/15] util/mmap-alloc: Factor out activating of memory to mmap_activate(), David Hildenbrand, 2020/03/05
- [PATCH v4 10/15] util/mmap-alloc: Prepare for resizeable mmaps, David Hildenbrand, 2020/03/05
- [PATCH v4 11/15] util/mmap-alloc: Implement resizeable mmaps, David Hildenbrand, 2020/03/05
- [PATCH v4 07/15] util/mmap-alloc: Factor out calculation of the pagesize for the guard page, David Hildenbrand, 2020/03/05
- Re: [PATCH v4 07/15] util/mmap-alloc: Factor out calculation of the pagesize for the guard page,
Murilo Opsfelder Araújo <=
- [PATCH v4 13/15] util: oslib: Resizeable anonymous allocations under POSIX, David Hildenbrand, 2020/03/05
- [PATCH v4 12/15] util: vfio-helpers: Implement ram_block_resized(), David Hildenbrand, 2020/03/05
- [PATCH v4 14/15] numa: Introduce ram_block_notifiers_support_resize(), David Hildenbrand, 2020/03/05
- [PATCH v4 15/15] exec: Ram blocks with resizeable anonymous allocations under POSIX, David Hildenbrand, 2020/03/05