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113 lines
4.5 KiB
113 lines
4.5 KiB
9 months ago
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From 633c6a52ac88526534466ae311522fe5447bcf91 Mon Sep 17 00:00:00 2001
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From: David Hildenbrand <david@redhat.com>
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Date: Wed, 17 Jan 2024 14:55:54 +0100
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Subject: [PATCH 02/22] memory-device: reintroduce memory region size check
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RH-Author: David Hildenbrand <david@redhat.com>
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RH-MergeRequest: 221: memory-device: reintroduce memory region size check
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RH-Jira: RHEL-20341
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
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RH-Commit: [2/2] e9ff2339b0c07c3f48f5834c9c80cd6d4cbc8f71
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JIRA: https://issues.redhat.com/browse/RHEL-20341
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We used to check that the memory region size is multiples of the overall
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requested address alignment for the device memory address.
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We removed that check, because there are cases (i.e., hv-balloon) where
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devices unconditionally request an address alignment that has a very large
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alignment (i.e., 32 GiB), but the actual memory device size might not be
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multiples of that alignment.
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However, this change:
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(a) allows for some practically impossible DIMM sizes, like "1GB+1 byte".
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(b) allows for DIMMs that partially cover hugetlb pages, previously
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reported in [1].
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Both scenarios don't make any sense: we might even waste memory.
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So let's reintroduce that check, but only check that the
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memory region size is multiples of the memory region alignment (i.e.,
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page size, huge page size), but not any additional memory device
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requirements communicated using md->get_min_alignment().
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The following examples now fail again as expected:
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(a) 1M with 2M THP
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qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \
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-object memory-backend-ram,id=mem1,size=1M \
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-device pc-dimm,id=dimm1,memdev=mem1
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-> backend memory size must be multiple of 0x200000
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(b) 1G+1byte
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qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \
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-object memory-backend-ram,id=mem1,size=1073741825B \
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-device pc-dimm,id=dimm1,memdev=mem1
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-> backend memory size must be multiple of 0x200000
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(c) Unliagned hugetlb size (2M)
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qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \
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-object memory-backend-file,id=mem1,mem-path=/dev/hugepages/tmp,size=511M \
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-device pc-dimm,id=dimm1,memdev=mem1
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backend memory size must be multiple of 0x200000
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(d) Unliagned hugetlb size (1G)
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qemu-system-x86_64 -m 4g,maxmem=16g,slots=1 -S -nodefaults -nographic \
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-object memory-backend-file,id=mem1,mem-path=/dev/hugepages1G/tmp,size=2047M \
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-device pc-dimm,id=dimm1,memdev=mem1
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-> backend memory size must be multiple of 0x40000000
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Note that this fix depends on a hv-balloon change to communicate its
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additional alignment requirements using get_min_alignment() instead of
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through the memory region.
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[1] https://lkml.kernel.org/r/f77d641d500324525ac036fe1827b3070de75fc1.1701088320.git.mprivozn@redhat.com
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Message-ID: <20240117135554.787344-3-david@redhat.com>
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Reported-by: Zhenyu Zhang <zhenyzha@redhat.com>
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Reported-by: Michal Privoznik <mprivozn@redhat.com>
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Fixes: eb1b7c4bd413 ("memory-device: Drop size alignment check")
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Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
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Tested-by: Mario Casquero <mcasquer@redhat.com>
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Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
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Signed-off-by: David Hildenbrand <david@redhat.com>
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(cherry picked from commit 540a1abbf0b243e4cfb4333c5d30a041f7080ba4)
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Signed-off-by: David Hildenbrand <david@redhat.com>
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---
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hw/mem/memory-device.c | 14 ++++++++++++++
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1 file changed, 14 insertions(+)
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diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
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index a1b1af26bc..e098585cda 100644
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--- a/hw/mem/memory-device.c
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+++ b/hw/mem/memory-device.c
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@@ -374,6 +374,20 @@ void memory_device_pre_plug(MemoryDeviceState *md, MachineState *ms,
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goto out;
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}
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+ /*
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+ * We always want the memory region size to be multiples of the memory
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+ * region alignment: for example, DIMMs with 1G+1byte size don't make
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+ * any sense. Note that we don't check that the size is multiples
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+ * of any additional alignment requirements the memory device might
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+ * have when it comes to the address in physical address space.
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+ */
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+ if (!QEMU_IS_ALIGNED(memory_region_size(mr),
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+ memory_region_get_alignment(mr))) {
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+ error_setg(errp, "backend memory size must be multiple of 0x%"
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+ PRIx64, memory_region_get_alignment(mr));
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+ return;
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+ }
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+
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if (legacy_align) {
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align = *legacy_align;
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} else {
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--
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2.39.3
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