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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7b9ac47a6cdsm1201100185a.93.2025.01.02.11.48.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jan 2025 11:48:39 -0800 (PST) Date: Thu, 2 Jan 2025 14:48:36 -0500 From: Peter Xu To: Steven Sistare Cc: qemu-devel@nongnu.org, Fabiano Rosas , David Hildenbrand , Marcel Apfelbaum , Eduardo Habkost , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" , Markus Armbruster Subject: Re: [PATCH V5 02/23] physmem: qemu_ram_alloc_from_fd extensions Message-ID: References: <1735057028-308595-1-git-send-email-steven.sistare@oracle.com> <1735057028-308595-3-git-send-email-steven.sistare@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.185, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Jan 02, 2025 at 01:36:01PM -0500, Steven Sistare wrote: > On 12/24/2024 12:18 PM, Peter Xu wrote: > > On Tue, Dec 24, 2024 at 08:16:47AM -0800, Steve Sistare wrote: > > > Extend qemu_ram_alloc_from_fd to support resizable ram, and define > > > qemu_ram_resize_cb to clean up the API. > > > > > > Add a grow parameter to extend the file if necessary. However, if > > > grow is false, a zero-sized file is always extended. > > > > > > Signed-off-by: Steve Sistare > > > --- > > > include/exec/ram_addr.h | 13 +++++++++---- > > > system/memory.c | 4 ++-- > > > system/physmem.c | 35 ++++++++++++++++++++--------------- > > > 3 files changed, 31 insertions(+), 21 deletions(-) > > > > > > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > > > index ff157c1..94bb3cc 100644 > > > --- a/include/exec/ram_addr.h > > > +++ b/include/exec/ram_addr.h > > > @@ -111,23 +111,30 @@ long qemu_maxrampagesize(void); > > > * > > > * Parameters: > > > * @size: the size in bytes of the ram block > > > + * @max_size: the maximum size of the block after resizing > > > * @mr: the memory region where the ram block is > > > + * @resized: callback after calls to qemu_ram_resize > > > * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM, > > > * RAM_NORESERVE, RAM_PROTECTED, RAM_NAMED_FILE, RAM_READONLY, > > > * RAM_READONLY_FD, RAM_GUEST_MEMFD > > > * @mem_path or @fd: specify the backing file or device > > > * @offset: Offset into target file > > > + * @grow: extend file if necessary (but an empty file is always extended). > > > * @errp: pointer to Error*, to store an error if it happens > > > * > > > * Return: > > > * On success, return a pointer to the ram block. > > > * On failure, return NULL. > > > */ > > > +typedef void (*qemu_ram_resize_cb)(const char *, uint64_t length, void *host); > > > + > > > RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, > > > uint32_t ram_flags, const char *mem_path, > > > off_t offset, Error **errp); > > > -RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > > > +RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, ram_addr_t max_size, > > > + qemu_ram_resize_cb resized, MemoryRegion *mr, > > > uint32_t ram_flags, int fd, off_t offset, > > > + bool grow, > > > Error **errp); > > > RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, > > > @@ -135,9 +142,7 @@ 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); > > > RAMBlock *qemu_ram_alloc_resizeable(ram_addr_t size, ram_addr_t max_size, > > > - void (*resized)(const char*, > > > - uint64_t length, > > > - void *host), > > > + qemu_ram_resize_cb resized, > > > MemoryRegion *mr, Error **errp); > > > void qemu_ram_free(RAMBlock *block); > > > diff --git a/system/memory.c b/system/memory.c > > > index 78e17e0..290c522 100644 > > > --- a/system/memory.c > > > +++ b/system/memory.c > > > @@ -1680,8 +1680,8 @@ bool memory_region_init_ram_from_fd(MemoryRegion *mr, > > > mr->readonly = !!(ram_flags & RAM_READONLY); > > > mr->terminates = true; > > > mr->destructor = memory_region_destructor_ram; > > > - mr->ram_block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, offset, > > > - &err); > > > + mr->ram_block = qemu_ram_alloc_from_fd(size, size, NULL, mr, ram_flags, fd, > > > + offset, false, &err); > > > if (err) { > > > mr->size = int128_zero(); > > > object_unparent(OBJECT(mr)); > > > diff --git a/system/physmem.c b/system/physmem.c > > > index c76503a..48c544f 100644 > > > --- a/system/physmem.c > > > +++ b/system/physmem.c > > > @@ -1942,8 +1942,10 @@ out_free: > > > } > > > #ifdef CONFIG_POSIX > > > -RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > > > +RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, ram_addr_t max_size, > > > + qemu_ram_resize_cb resized, MemoryRegion *mr, > > > uint32_t ram_flags, int fd, off_t offset, > > > + bool grow, > > > Error **errp) > > > { > > > RAMBlock *new_block; > > > @@ -1953,7 +1955,9 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > > > /* Just support these ram flags by now. */ > > > assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE | > > > RAM_PROTECTED | RAM_NAMED_FILE | RAM_READONLY | > > > - RAM_READONLY_FD | RAM_GUEST_MEMFD)) == 0); > > > + RAM_READONLY_FD | RAM_GUEST_MEMFD | > > > + RAM_RESIZEABLE)) == 0); > > > + assert(max_size >= size); > > > if (xen_enabled()) { > > > error_setg(errp, "-mem-path not supported with Xen"); > > > @@ -1968,12 +1972,14 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > > > size = TARGET_PAGE_ALIGN(size); > > > size = REAL_HOST_PAGE_ALIGN(size); > > > + max_size = TARGET_PAGE_ALIGN(max_size); > > > + max_size = REAL_HOST_PAGE_ALIGN(max_size); > > > file_size = get_file_size(fd); > > > - if (file_size > offset && file_size < (offset + size)) { > > > + if (file_size && file_size < offset + max_size && !grow) { > > > > Is this a bugfix for the case offset < fsize? If so, better make it a > > small patch and copy stable.. > > > > $ touch ramfile > > $ truncate -s 64M ramfile > > $ ./qemu-system-x86_64 -object memory-backend-file,mem-path=./ramfile,offset=128M,size=128M,id=mem1,prealloc=on > > qemu-system-x86_64: qemu_prealloc_mem: preallocating memory failed: Bad address > > > > So yes, it's a bug.. > > Yes, it's a bug I noticed by inspection. > I will split and submit to stable. Thanks. > > > > error_setg(errp, "backing store size 0x%" PRIx64 > > > " does not match 'size' option 0x" RAM_ADDR_FMT, > > > - file_size, size); > > > + file_size, max_size); > > > return NULL; > > > } > > > @@ -1988,11 +1994,13 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > > > new_block = g_malloc0(sizeof(*new_block)); > > > new_block->mr = mr; > > > new_block->used_length = size; > > > - new_block->max_length = size; > > > + new_block->max_length = max_size; > > > + new_block->resized = resized; > > > new_block->flags = ram_flags; > > > new_block->guest_memfd = -1; > > > - new_block->host = file_ram_alloc(new_block, size, fd, !file_size, offset, > > > - errp); > > > + new_block->host = file_ram_alloc(new_block, max_size, fd, > > > + file_size < offset + max_size, > > > > Same here, looks like relevant to above. > > This line would not be part of the fix for stable. The pre-cpr code should only > truncate (allocate) if !file_size. If file_size > 0, the fixed conditional above > verifies that file_size is large enough. > > The fix will be a 1-liner: > - if (file_size > offset && file_size < (offset + size)) { > + if (file_size && file_size < offset + size) { Indeed, this should work. -- Peter Xu