On 2019/4/2 19:06, Suzuki K Poulose wrote:
With commit a80868f398554842b14, we no longer ensure that the
THP page is properly aligned in the guest IPA. Skip the stage2
huge mapping for unaligned IPA backed by transparent hugepages.
Fixes: a80868f398554842b14 ("KVM: arm/arm64: Enforce PTE mappings at stage2 when needed")
Reported-by: Eric Auger <eric.auger@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Chirstoffer Dall <christoffer.dall@xxxxxxx>
Cc: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Cc: Zheng Xiang <zhengxiang9@xxxxxxxxxx>
Tested-by: Eric Auger <eric.auger@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Hi Suzuki,
Why not making use of fault_supports_stage2_huge_mapping()? Let it do
some checks for us.
fault_supports_stage2_huge_mapping() was intended to do a *two-step*
check to tell us that can we create stage2 huge block mappings, and this
check is both for hugetlbfs and THP. With commit a80868f398554842b14,
we pass PAGE_SIZE as "map_size" for normal size pages (which turned out
to be almost meaningless), and unfortunately the THP check no longer
works.
So we want to rework *THP* check process. Your patch fixes the first
checking-step, but the second is still missed, am I wrong?
Can you please give a look at the below diff?
thanks,
zenghui
---
virt/kvm/arm/mmu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 27c9583..4a22f5b 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1412,7 +1412,9 @@ static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
* page accordingly.
*/
mask = PTRS_PER_PMD - 1;
- VM_BUG_ON((gfn & mask) != (pfn & mask));
Somehow, I'd prefer keeping the VM_BUG_ON() here, let it report some
potential issues in the future (of course I hope none:) )
+ /* Skip memslots with unaligned IPA and user address */
+ if ((gfn & mask) != (pfn & mask))
+ return false;
if (pfn & mask) {
*ipap &= PMD_MASK;
kvm_release_pfn_clean(pfn);
---8>---
Rework fault_supports_stage2_huge_mapping(), let it check THP again.
Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
---
virt/kvm/arm/mmu.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 27c9583..5e1b258 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1632,6 +1632,15 @@ static bool
fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
uaddr_end = uaddr_start + size;
/*
+ * If the memslot is _not_ backed by hugetlbfs, then check if it
+ * can be backed by transparent hugepages.
+ *
+ * Currently only PMD_SIZE THPs are supported, revisit it later.
+ */
+ if (map_size == PAGE_SIZE)
+ map_size = PMD_SIZE;
+
+ /*
* Pages belonging to memslots that don't have the same alignment
* within a PMD/PUD for userspace and IPA cannot be mapped with stage-2
* PMD/PUD entries, because we'll end up mapping the wrong pages.
@@ -1643,7 +1652,7 @@ static bool
fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
* |abcde|fgh Stage-1 block | Stage-1 block tv|xyz|
* +-----+--------------------+--------------------+---+
*
- * memslot->base_gfn << PAGE_SIZE:
+ * memslot->base_gfn << PAGE_SHIFT:
* +---+--------------------+--------------------+-----+
* |abc|def Stage-2 block | Stage-2 block |tvxyz|
* +---+--------------------+--------------------+-----+
--
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