[PATCH v1 2/2] memory-device: reintroduce memory region size check Test on 64k basic page size aarch64 The patches work well on my Ampere host. The test results are as expected.
(a) 1M with 512M THP /home/zhenyzha/sandbox/qemu.main/build/qemu-system-aarch64 \ -name 'avocado-vt-vm1' \ -sandbox on \ : -nodefaults \ -m 4096,maxmem=32G,slots=4 \ -object memory-backend-ram,id=mem1,size=1M \ -device pc-dimm,id=dimm1,memdev=mem1 \ -smp 4 \ -cpu 'host' \ -accel kvm \ -monitor stdio -> backend memory size must be multiple of 0x200000 (b) 1G+1byte /home/zhenyzha/sandbox/qemu.main/build/qemu-system-aarch64 \ -name 'avocado-vt-vm1' \ -sandbox on \ : -nodefaults \ -m 4096,maxmem=32G,slots=4 \ -object memory-backend-ram,id=mem1,size=1073741825B \ -device pc-dimm,id=dimm1,memdev=mem1 \ -smp 4 \ -cpu 'host' \ -accel kvm \ -monitor stdio -> backend memory size must be multiple of 0x200000 (c) Unliagned hugetlb size (2M) /home/zhenyzha/sandbox/qemu.main/build/qemu-system-aarch64 \ -name 'avocado-vt-vm1' \ -sandbox on \ : -nodefaults \ -m 4096,maxmem=32G,slots=4 \ -object memory-backend-file,id=mem1,prealloc=yes,mem-path=/mnt/kvm_hugepage,size=2047M \ -device pc-dimm,id=dimm1,memdev=mem1 \ -smp 4 \ -cpu 'host' \ -accel kvm \ -monitor stdio -> backend memory size must be multiple of 0x200000 (d) 2M with 512M hugetlb size /home/zhenyzha/sandbox/qemu.main/build/qemu-system-aarch64 \ -name 'avocado-vt-vm1' \ -sandbox on \ : -nodefaults \ -m 4096,maxmem=32G,slots=4 \ -object memory-backend-file,id=mem1,mem-path=/dev/hugepages/tmp,size=2M \ -device pc-dimm,id=dimm1,memdev=mem1 \ -smp 4 \ -cpu 'host' \ -accel kvm \ -monitor stdio -> memory size 0x200000 must be equal to or larger than page size 0x20000000 (e) 511M with 512M hugetlb size /home/zhenyzha/sandbox/qemu.main/build/qemu-system-aarch64 \ -name 'avocado-vt-vm1' \ -sandbox on \ : -nodefaults \ -m 4096,maxmem=32G,slots=4 \ -object memory-backend-file,id=mem1,mem-path=/dev/hugepages/tmp,size=511M \ -device pc-dimm,id=dimm1,memdev=mem1 \ -smp 4 \ -cpu 'host' \ -accel kvm \ -monitor stdio -> memory size 0x1ff00000 must be equal to or larger than page size 0x20000000 Tested-by: Zhenyu Zhang <zhen...@redhat.com> On Wed, Jan 17, 2024 at 9:56 PM David Hildenbrand <da...@redhat.com> wrote: > > 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.mpriv...@redhat.com > > Reported-by: Zhenyu Zhang <zheny...@redhat.com> > Reported-by: Michal Privoznik <mpriv...@redhat.com> > Fixes: eb1b7c4bd413 ("memory-device: Drop size alignment check") > Signed-off-by: David Hildenbrand <da...@redhat.com> > --- > 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 { > -- > 2.43.0 >
