From 8dbe22c6868b8a5efd1df3d0c5150524fabe61ff Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 10 May 2021 13:43:21 +0200 Subject: memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Let's introduce RAM_NORESERVE, allowing mmap'ing with MAP_NORESERVE. The new flag has the following semantics: " RAM is mmap-ed with MAP_NORESERVE. When set, reserving swap space (or huge pages if applicable) is skipped: will bail out if not supported. When not set, the OS will do the reservation, if supported for the memory type. " Allow passing it into: - memory_region_init_ram_nomigrate() - memory_region_init_resizeable_ram() - memory_region_init_ram_from_file() ... and teach qemu_ram_mmap() and qemu_anon_ram_alloc() about the flag. Bail out if the flag is not supported, which is the case right now for both, POSIX and win32. We will add Linux support next and allow specifying RAM_NORESERVE via memory backends. The target use case is virtio-mem, which dynamically exposes memory inside a large, sparse memory area to the VM. Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Peter Xu Acked-by: Eduardo Habkost for memory backend and machine core Signed-off-by: David Hildenbrand Message-Id: <20210510114328.21835-9-david@redhat.com> Signed-off-by: Paolo Bonzini --- softmmu/physmem.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'softmmu') diff --git a/softmmu/physmem.c b/softmmu/physmem.c index a110aa6..11ea8e1 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -1591,6 +1591,7 @@ static void *file_ram_alloc(RAMBlock *block, qemu_map_flags = readonly ? QEMU_MAP_READONLY : 0; qemu_map_flags |= (block->flags & RAM_SHARED) ? QEMU_MAP_SHARED : 0; qemu_map_flags |= (block->flags & RAM_PMEM) ? QEMU_MAP_SYNC : 0; + qemu_map_flags |= (block->flags & RAM_NORESERVE) ? QEMU_MAP_NORESERVE : 0; area = qemu_ram_mmap(fd, memory, block->mr->align, qemu_map_flags, offset); if (area == MAP_FAILED) { error_setg_errno(errp, errno, @@ -1716,6 +1717,11 @@ bool qemu_ram_is_shared(RAMBlock *rb) return rb->flags & RAM_SHARED; } +bool qemu_ram_is_noreserve(RAMBlock *rb) +{ + return rb->flags & RAM_NORESERVE; +} + /* Note: Only set at the start of postcopy */ bool qemu_ram_is_uf_zeroable(RAMBlock *rb) { @@ -1950,6 +1956,7 @@ static void dirty_memory_extend(ram_addr_t old_ram_size, static void ram_block_add(RAMBlock *new_block, Error **errp) { + const bool noreserve = qemu_ram_is_noreserve(new_block); const bool shared = qemu_ram_is_shared(new_block); RAMBlock *block; RAMBlock *last_block = NULL; @@ -1973,7 +1980,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) } else { new_block->host = qemu_anon_ram_alloc(new_block->max_length, &new_block->mr->align, - shared); + shared, noreserve); if (!new_block->host) { error_setg_errno(errp, errno, "cannot set up guest memory '%s'", @@ -2045,7 +2052,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, int64_t file_size, file_align; /* Just support these ram flags by now. */ - assert((ram_flags & ~(RAM_SHARED | RAM_PMEM)) == 0); + assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE)) == 0); if (xen_enabled()) { error_setg(errp, "-mem-path not supported with Xen"); @@ -2137,6 +2144,8 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size, Error *local_err = NULL; assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0); + assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC | + RAM_NORESERVE)) == 0); assert(!host ^ (ram_flags & RAM_PREALLOC)); size = HOST_PAGE_ALIGN(size); @@ -2170,7 +2179,7 @@ RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, RAMBlock *qemu_ram_alloc(ram_addr_t size, uint32_t ram_flags, MemoryRegion *mr, Error **errp) { - assert((ram_flags & ~RAM_SHARED) == 0); + assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE)) == 0); return qemu_ram_alloc_internal(size, size, NULL, NULL, ram_flags, mr, errp); } -- cgit v1.1