On Mon, Apr 01, 2019 at 07:10:37PM +0200, Auger Eric wrote:
> Hi Suzuki,
>
> On 3/28/19 2:36 PM, Marc Zyngier wrote:
> > From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> >
> > commit 6794ad5443a2118 ("KVM: arm/arm64: Fix unintended stage 2 PMD mappings")
> > made the checks to skip huge mappings, stricter. However it introduced
> > a bug where we still use huge mappings, ignoring the flag to
> > use PTE mappings, by not reseting the vma_pagesize to PAGE_SIZE.
> >
> > Also, the checks do not cover the PUD huge pages, that was
> > under review during the same period. This patch fixes both
> > the issues.
>
> I face a regression with this patch. My guest gets stuck. I am running
> on AMD Seattle. Reverting the patch makes things work again for me. I
> run with qemu. In this scenario I don't use hugepages. I use 64kB page
> size for both the host and guest.
Hi Eric,
Thanks for the testing. Does the following patch fix the issue for you ?
---8>---
kvm: arm: Skip transparent huge pages in unaligned memslots
We silently create stage2 huge mappings for a memslot with
unaligned IPA and user address.
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
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));
+ /* 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);
--
2.7.4
Kind regards
Suzuki
>
> Thanks
>
> Eric
> >
> > Fixes : 6794ad5443a2118 ("KVM: arm/arm64: Fix unintended stage 2 PMD mappings")
> > Reported-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
> > Cc: Zenghui Yu <yuzenghui@xxxxxxxxxx>
> > Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> > ---
> > virt/kvm/arm/mmu.c | 43 +++++++++++++++++++++----------------------
> > 1 file changed, 21 insertions(+), 22 deletions(-)
> >
> > diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> > index ffd7acdceac7..bcdf978c0d1d 100644
> > --- a/virt/kvm/arm/mmu.c
> > +++ b/virt/kvm/arm/mmu.c
> > @@ -1594,8 +1594,9 @@ static void kvm_send_hwpoison_signal(unsigned long address,
> > send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current);
> > }
> >
> > -static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
> > - unsigned long hva)
> > +static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
> > + unsigned long hva,
> > + unsigned long map_size)
> > {
> > gpa_t gpa_start;
> > hva_t uaddr_start, uaddr_end;
> > @@ -1610,34 +1611,34 @@ static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
> >
> > /*
> > * Pages belonging to memslots that don't have the same alignment
> > - * within a PMD for userspace and IPA cannot be mapped with stage-2
> > - * PMD entries, because we'll end up mapping the wrong pages.
> > + * 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.
> > *
> > * Consider a layout like the following:
> > *
> > * memslot->userspace_addr:
> > * +-----+--------------------+--------------------+---+
> > - * |abcde|fgh Stage-1 PMD | Stage-1 PMD tv|xyz|
> > + * |abcde|fgh Stage-1 block | Stage-1 block tv|xyz|
> > * +-----+--------------------+--------------------+---+
> > *
> > * memslot->base_gfn << PAGE_SIZE:
> > * +---+--------------------+--------------------+-----+
> > - * |abc|def Stage-2 PMD | Stage-2 PMD |tvxyz|
> > + * |abc|def Stage-2 block | Stage-2 block |tvxyz|
> > * +---+--------------------+--------------------+-----+
> > *
> > - * If we create those stage-2 PMDs, we'll end up with this incorrect
> > + * If we create those stage-2 blocks, we'll end up with this incorrect
> > * mapping:
> > * d -> f
> > * e -> g
> > * f -> h
> > */
> > - if ((gpa_start & ~S2_PMD_MASK) != (uaddr_start & ~S2_PMD_MASK))
> > + if ((gpa_start & (map_size - 1)) != (uaddr_start & (map_size - 1)))
> > return false;
> >
> > /*
> > * Next, let's make sure we're not trying to map anything not covered
> > - * by the memslot. This means we have to prohibit PMD size mappings
> > - * for the beginning and end of a non-PMD aligned and non-PMD sized
> > + * by the memslot. This means we have to prohibit block size mappings
> > + * for the beginning and end of a non-block aligned and non-block sized
> > * memory slot (illustrated by the head and tail parts of the
> > * userspace view above containing pages 'abcde' and 'xyz',
> > * respectively).
> > @@ -1646,8 +1647,8 @@ static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
> > * userspace_addr or the base_gfn, as both are equally aligned (per
> > * the check above) and equally sized.
> > */
> > - return (hva & S2_PMD_MASK) >= uaddr_start &&
> > - (hva & S2_PMD_MASK) + S2_PMD_SIZE <= uaddr_end;
> > + return (hva & ~(map_size - 1)) >= uaddr_start &&
> > + (hva & ~(map_size - 1)) + map_size <= uaddr_end;
> > }
> >
> > static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > @@ -1676,12 +1677,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > return -EFAULT;
> > }
> >
> > - if (!fault_supports_stage2_pmd_mappings(memslot, hva))
> > - force_pte = true;
> > -
> > - if (logging_active)
> > - force_pte = true;
> > -
> > /* Let's check if we will get back a huge page backed by hugetlbfs */
> > down_read(¤t->mm->mmap_sem);
> > vma = find_vma_intersection(current->mm, hva, hva + 1);
> > @@ -1692,6 +1687,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > }
> >
> > vma_pagesize = vma_kernel_pagesize(vma);
> > + if (logging_active ||
> > + !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
> > + force_pte = true;
> > + vma_pagesize = PAGE_SIZE;
> > + }
> > +
> > /*
> > * The stage2 has a minimum of 2 level table (For arm64 see
> > * kvm_arm_setup_stage2()). Hence, we are guaranteed that we can
> > @@ -1699,11 +1700,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > * As for PUD huge maps, we must make sure that we have at least
> > * 3 levels, i.e, PMD is not folded.
> > */
> > - if ((vma_pagesize == PMD_SIZE ||
> > - (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) &&
> > - !force_pte) {
> > + if (vma_pagesize == PMD_SIZE ||
> > + (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm)))
> > gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
> > - }
> > up_read(¤t->mm->mmap_sem);
> >
> > /* We need minimum second+third level pages */
> >
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