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Re: [PATCH v4 11/15] util/mmap-alloc: Implement resizeable mmaps
From: |
Murilo Opsfelder Araújo |
Subject: |
Re: [PATCH v4 11/15] util/mmap-alloc: Implement resizeable mmaps |
Date: |
Wed, 25 Mar 2020 12:14:18 -0300 |
On Thursday, March 5, 2020 11:29:41 AM -03 David Hildenbrand wrote:
> Implement resizeable mmaps. For now, the actual resizing is not wired up.
> Introduce qemu_ram_mmap_resizeable() and qemu_ram_mmap_resize(). Make
> qemu_ram_mmap() a wrapper of qemu_ram_mmap_resizeable().
>
> Reviewed-by: Peter Xu <address@hidden>
> Cc: Richard Henderson <address@hidden>
> Cc: Igor Kotrasinski <address@hidden>
> Cc: Murilo Opsfelder Araujo <address@hidden>
> Cc: "Michael S. Tsirkin" <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>
> include/qemu/mmap-alloc.h | 21 +++++++++++--------
> util/mmap-alloc.c | 43 ++++++++++++++++++++++++++++-----------
> 2 files changed, 44 insertions(+), 20 deletions(-)
>
> diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
> index e786266b92..ca8f7edf70 100644
> --- a/include/qemu/mmap-alloc.h
> +++ b/include/qemu/mmap-alloc.h
> @@ -7,11 +7,13 @@ size_t qemu_fd_getpagesize(int fd);
> size_t qemu_mempath_getpagesize(const char *mem_path);
>
> /**
> - * qemu_ram_mmap: mmap the specified file or device.
> + * qemu_ram_mmap_resizeable: reserve a memory region of @max_size to mmap
> the + * specified file or device and mmap @size
> of it. *
> * Parameters:
> * @fd: the file or the device to mmap
> * @size: the number of bytes to be mmaped
> + * @max_size: the number of bytes to be reserved
> * @align: if not zero, specify the alignment of the starting mapping
> address; * otherwise, the alignment in use will be determined by
> QEMU. * @shared: map has RAM_SHARED flag.
> @@ -21,12 +23,15 @@ size_t qemu_mempath_getpagesize(const char *mem_path);
> * 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,
> - bool shared,
> - bool is_pmem);
> -
> -void qemu_ram_munmap(int fd, void *ptr, size_t size);
> +void *qemu_ram_mmap_resizeable(int fd, size_t size, size_t max_size,
> + size_t align, bool shared, bool is_pmem);
> +bool qemu_ram_mmap_resize(void *ptr, int fd, size_t old_size, size_t
> new_size, + bool shared, bool is_pmem);
> +static inline void *qemu_ram_mmap(int fd, size_t size, size_t align,
> + bool shared, bool is_pmem)
> +{
> + return qemu_ram_mmap_resizeable(fd, size, size, align, shared,
> is_pmem); +}
> +void qemu_ram_munmap(int fd, void *ptr, size_t max_size);
>
> #endif
> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> index 2767caa33b..7ed85f16d3 100644
> --- a/util/mmap-alloc.c
> +++ b/util/mmap-alloc.c
> @@ -174,11 +174,8 @@ static inline size_t mmap_guard_pagesize(int fd)
> #endif
> }
>
> -void *qemu_ram_mmap(int fd,
> - size_t size,
> - size_t align,
> - bool shared,
> - bool is_pmem)
> +void *qemu_ram_mmap_resizeable(int fd, size_t size, size_t max_size,
> + size_t align, bool shared, bool is_pmem)
> {
> const size_t guard_pagesize = mmap_guard_pagesize(fd);
> const size_t pagesize = qemu_fd_getpagesize(fd);
> @@ -186,12 +183,14 @@ void *qemu_ram_mmap(int fd,
> void *ptr, *guardptr;
>
> g_assert(QEMU_IS_ALIGNED(size, pagesize));
> + g_assert(QEMU_IS_ALIGNED(max_size, pagesize));
>
> /*
> * Note: this always allocates at least one extra page of virtual
> address - * space, even if size is already aligned.
> + * space, even if the size is already aligned. We will reserve an area
> of + * at least max_size, but only activate the requested part of it.
> */
> - total = size + align;
> + total = max_size + align;
>
> guardptr = mmap_reserve(NULL, total, fd);
> if (guardptr == MAP_FAILED) {
> @@ -219,21 +218,41 @@ void *qemu_ram_mmap(int fd,
> * a guard page guarding against potential buffer overflows.
> */
> total -= offset;
> - if (total > size + guard_pagesize) {
> - munmap(ptr + size + guard_pagesize, total - size - guard_pagesize);
> + if (total > max_size + guard_pagesize) {
> + munmap(ptr + max_size + guard_pagesize,
> + total - max_size - guard_pagesize);
> }
>
> return ptr;
> }
>
> -void qemu_ram_munmap(int fd, void *ptr, size_t size)
> +bool qemu_ram_mmap_resize(void *ptr, int fd, size_t old_size, size_t
> new_size, + bool shared, bool is_pmem)
> {
> const size_t pagesize = qemu_fd_getpagesize(fd);
>
> - g_assert(QEMU_IS_ALIGNED(size, pagesize));
> + g_assert(QEMU_IS_ALIGNED(old_size, pagesize));
> + g_assert(QEMU_IS_ALIGNED(new_size, pagesize));
> +
> + if (old_size < new_size) {
> + /* activate the missing piece in the reserved area */
> + ptr = mmap_activate(ptr + old_size, new_size - old_size, fd,
> old_size, + shared, is_pmem);
> + } else if (old_size > new_size) {
> + /* discard this piece, marking it reserved */
> + ptr = mmap_reserve(ptr + new_size, old_size - new_size, fd);
> + }
> + return ptr != MAP_FAILED;
> +}
> +
> +void qemu_ram_munmap(int fd, void *ptr, size_t max_size)
> +{
> + const size_t pagesize = qemu_fd_getpagesize(fd);
> +
> + g_assert(QEMU_IS_ALIGNED(max_size, pagesize));
>
> if (ptr) {
> /* Unmap both the RAM block and the guard page */
> - munmap(ptr, size + mmap_guard_pagesize(fd));
> + munmap(ptr, max_size + mmap_guard_pagesize(fd));
> }
> }
--
Murilo
- [PATCH v4 03/15] util: vfio-helpers: Factor out removal from qemu_vfio_undo_mapping(), (continued)
- [PATCH v4 03/15] util: vfio-helpers: Factor out removal from qemu_vfio_undo_mapping(), David Hildenbrand, 2020/03/05
- [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
- Re: [PATCH v4 11/15] util/mmap-alloc: Implement resizeable mmaps,
Murilo Opsfelder Araújo <=
- [PATCH v4 07/15] util/mmap-alloc: Factor out calculation of the pagesize for the guard page, David Hildenbrand, 2020/03/05
- [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