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Szmigiero" , Mario Casquero , Igor Mammedov , Xiao Guangrong , Zhenyu Zhang , Michal Privoznik Subject: [PATCH v1 2/2] memory-device: reintroduce memory region size check Date: Wed, 17 Jan 2024 14:55:54 +0100 Message-ID: <20240117135554.787344-3-david@redhat.com> In-Reply-To: <20240117135554.787344-1-david@redhat.com> References: <20240117135554.787344-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -38 X-Spam_score: -3.9 X-Spam_bar: --- X-Spam_report: (-3.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.806, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 We used to check that the memory region size is multiples of the overall requested address alignment for the device memory address. We removed that check, because there are cases (i.e., hv-balloon) where devices unconditionally request an address alignment that has a very large alignment (i.e., 32 GiB), but the actual memory device size might not be multiples of that alignment. However, this change: (a) allows for some practically impossible DIMM sizes, like "1GB+1 byte". (b) allows for DIMMs that partially cover hugetlb pages, previously reported in [1]. Both scenarios don't make any sense: we might even waste memory. So let's reintroduce that check, but only check that the memory region size is multiples of the memory region alignment (i.e., page size, huge page size), but not any additional memory device requirements communicated using md->get_min_alignment(). The following examples now fail again as expected: (a) 1M with 2M THP qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \ -object memory-backend-ram,id=mem1,size=1M \ -device pc-dimm,id=dimm1,memdev=mem1 -> backend memory size must be multiple of 0x200000 (b) 1G+1byte qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \ -object memory-backend-ram,id=mem1,size=1073741825B \ -device pc-dimm,id=dimm1,memdev=mem1 -> backend memory size must be multiple of 0x200000 (c) Unliagned hugetlb size (2M) qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \ -object memory-backend-file,id=mem1,mem-path=/dev/hugepages/tmp,size=511M \ -device pc-dimm,id=dimm1,memdev=mem1 backend memory size must be multiple of 0x200000 (d) Unliagned hugetlb size (1G) qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \ -object memory-backend-file,id=mem1,mem-path=/dev/hugepages1G/tmp,size=2047M \ -device pc-dimm,id=dimm1,memdev=mem1 -> backend memory size must be multiple of 0x40000000 Note that this fix depends on a hv-balloon change to communicate its additional alignment requirements using get_min_alignment() instead of through the memory region. [1] https://lkml.kernel.org/r/f77d641d500324525ac036fe1827b3070de75fc1.1701088320.git.mprivozn@redhat.com Reported-by: Zhenyu Zhang Reported-by: Michal Privoznik Fixes: eb1b7c4bd413 ("memory-device: Drop size alignment check") Signed-off-by: David Hildenbrand Tested-by: Zhenyu Zhang Tested-by: Mario Casquero --- hw/mem/memory-device.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c index a1b1af26bc..e098585cda 100644 --- a/hw/mem/memory-device.c +++ b/hw/mem/memory-device.c @@ -374,6 +374,20 @@ void memory_device_pre_plug(MemoryDeviceState *md, MachineState *ms, goto out; } + /* + * We always want the memory region size to be multiples of the memory + * region alignment: for example, DIMMs with 1G+1byte size don't make + * any sense. Note that we don't check that the size is multiples + * of any additional alignment requirements the memory device might + * have when it comes to the address in physical address space. + */ + if (!QEMU_IS_ALIGNED(memory_region_size(mr), + memory_region_get_alignment(mr))) { + error_setg(errp, "backend memory size must be multiple of 0x%" + PRIx64, memory_region_get_alignment(mr)); + return; + } + if (legacy_align) { align = *legacy_align; } else {