| Message ID | 1735850090-329906-1-git-send-email-steven.sistare@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | physmem: fix qemu_ram_alloc_from_fd size calculation | expand |
On Thu, Jan 02, 2025 at 12:34:50PM -0800, Steve Sistare wrote: > qemu_ram_alloc_from_fd allocates space if file_size == 0. If non-zero, > it uses the existing space and verifies it is large enough, but the > verification was broken when the offset parameter was introduced. As > a result, a file smaller than offset passes the verification and causes > errors later. Fix that, and update the error message to include offset. > > Peter provides this concise reproducer: > > $ 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 > > With the fix, the error message is: > qemu-system-x86_64: mem1 backing store size 0x4000000 is too small for 'size' option 0x8000000 plus 'offset' option 0x8000000 > Can have the cc tag here too to be super clear: Cc: qemu-stable@nongnu.org > Fixes: 4b870dc4d0c0 ("hostmem-file: add offset option") > Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Peter Xu <peterx@redhat.com> Please also feel free to attach this patch as the 1st patch when repost cpr-transfer, it could make dependency easier no matter how this would land. Maybe it'll be still easier to go via a migration pull that collects cpr transfer as a whole. May depend on whether there'll be a memory API pull before that.. Thanks,
On 1/2/2025 4:14 PM, Peter Xu wrote: > On Thu, Jan 02, 2025 at 12:34:50PM -0800, Steve Sistare wrote: >> qemu_ram_alloc_from_fd allocates space if file_size == 0. If non-zero, >> it uses the existing space and verifies it is large enough, but the >> verification was broken when the offset parameter was introduced. As >> a result, a file smaller than offset passes the verification and causes >> errors later. Fix that, and update the error message to include offset. >> >> Peter provides this concise reproducer: >> >> $ 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 >> >> With the fix, the error message is: >> qemu-system-x86_64: mem1 backing store size 0x4000000 is too small for 'size' option 0x8000000 plus 'offset' option 0x8000000 >> > > Can have the cc tag here too to be super clear: > > Cc: qemu-stable@nongnu.org Done and resubmitted. >> Fixes: 4b870dc4d0c0 ("hostmem-file: add offset option") >> Signed-off-by: Steve Sistare <steven.sistare@oracle.com> > > Reviewed-by: Peter Xu <peterx@redhat.com> > > Please also feel free to attach this patch as the 1st patch when repost > cpr-transfer, it could make dependency easier no matter how this would > land. Will do - steve > Maybe it'll be still easier to go via a migration pull that collects cpr > transfer as a whole. May depend on whether there'll be a memory API pull > before that..
diff --git a/system/physmem.c b/system/physmem.c index c76503a..f01325f 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -1970,10 +1970,11 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, size = REAL_HOST_PAGE_ALIGN(size); file_size = get_file_size(fd); - if (file_size > offset && file_size < (offset + size)) { - error_setg(errp, "backing store size 0x%" PRIx64 - " does not match 'size' option 0x" RAM_ADDR_FMT, - file_size, size); + if (file_size && file_size < offset + size) { + error_setg(errp, "%s backing store size 0x%" PRIx64 + " is too small for 'size' option 0x" RAM_ADDR_FMT + " plus 'offset' option 0x" RAM_ADDR_FMT, + memory_region_name(mr), file_size, size, offset); return NULL; }
qemu_ram_alloc_from_fd allocates space if file_size == 0. If non-zero, it uses the existing space and verifies it is large enough, but the verification was broken when the offset parameter was introduced. As a result, a file smaller than offset passes the verification and causes errors later. Fix that, and update the error message to include offset. Peter provides this concise reproducer: $ 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 With the fix, the error message is: qemu-system-x86_64: mem1 backing store size 0x4000000 is too small for 'size' option 0x8000000 plus 'offset' option 0x8000000 Fixes: 4b870dc4d0c0 ("hostmem-file: add offset option") Signed-off-by: Steve Sistare <steven.sistare@oracle.com> --- system/physmem.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)