On Sun, 25 Oct 2020 01:27:39 +0100,
Gavin Shan <gshan@xxxxxxxxxx> wrote:
>
> The huge page could be mapped through multiple contiguous PMDs or PTEs.
> The corresponding huge page sizes aren't supported by the page table
> walker currently.
>
> This fails the unsupported huge page sizes to the near one. Otherwise,
> the guest can't boot successfully: CONT_PMD_SHIFT and CONT_PTE_SHIFT
> fail back to PMD_SHIFT and PAGE_SHIFT separately.
>
> Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> ---
> arch/arm64/kvm/mmu.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 0f51585adc04..81cbdc368246 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -793,12 +793,20 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> vma_shift = PMD_SHIFT;
> #endif
>
> + if (vma_shift == CONT_PMD_SHIFT)
> + vma_shift = PMD_SHIFT;
> +
> if (vma_shift == PMD_SHIFT &&
> !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
> force_pte = true;
> vma_shift = PAGE_SHIFT;
> }
>
> + if (vma_shift == CONT_PTE_SHIFT) {
> + force_pte = true;
> + vma_shift = PAGE_SHIFT;
> + }
> +
> vma_pagesize = 1UL << vma_shift;
> if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE)
> fault_ipa &= ~(vma_pagesize - 1);
Yup, nice catch. However, I think we should take this opportunity to
rationalise the logic here, and catch future discrepancies (should
someone add contiguous PUD or something similarly silly). How about
something like this (untested):
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index cc323d96c9d4..d9a13a8a82e0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -787,14 +787,31 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
vma_shift = PAGE_SHIFT;
}
- if (vma_shift == PUD_SHIFT &&
- !fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
- vma_shift = PMD_SHIFT;
+ switch (vma_shift) {
+ case PUD_SHIFT:
+ if (fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
+ break;
+ fallthrough;
- if (vma_shift == PMD_SHIFT &&
- !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
- force_pte = true;
+ case CONT_PMD_SHIFT:
+ vma_shift = PMD_SHIFT;
+ fallthrough;
+
+ case PMD_SHIFT:
+ if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE))
+ break;
+ fallthrough;
+
+ case CONT_PTE_SHIFT:
vma_shift = PAGE_SHIFT;
+ force_pte = true;
+ fallthrough;
+
+ case PAGE_SHIFT:
+ break;
+
+ default:
+ WARN_ONCE(1, "Unknown vma_shift %d", vma_shift);
}
vma_pagesize = 1UL << vma_shift;
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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