Re: [Intel-gfx] [PATCH 4/6] KVM: arm64/mmu: avoid struct page in MMU

Marc Zyngier
2021-06-28T09:31:06Z

On Thu, 24 Jun 2021 04:57:47 +0100,
David Stevens <stevensd@chromium.org> wrote:
>
> From: David Stevens <stevensd@chromium.org>
>
> Avoid converting pfns returned by follow_fault_pfn to struct pages to
> transiently take a reference. The reference was originally taken to
> match the reference taken by gup. However, pfns returned by
> follow_fault_pfn may not have a struct page set up for reference
> counting.
>
> Signed-off-by: David Stevens <stevensd@chromium.org>
> ---
> arch/arm64/kvm/mmu.c | 43 +++++++++++++++++++++++--------------------
> 1 file changed, 23 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 896b3644b36f..a741972cb75f 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c

[...]

> @@ -968,16 +968,16 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> */
> if (vma_pagesize == PAGE_SIZE && !force_pte)
> vma_pagesize = transparent_hugepage_adjust(memslot, hva,
> - &pfn, &fault_ipa);
> + &pfnpg, &fault_ipa);
> if (writable)
> prot |= KVM_PGTABLE_PROT_W;
>
> if (fault_status != FSC_PERM && !device)
> - clean_dcache_guest_page(pfn, vma_pagesize);
> + clean_dcache_guest_page(pfnpg.pfn, vma_pagesize);
>
> if (exec_fault) {
> prot |= KVM_PGTABLE_PROT_X;
> - invalidate_icache_guest_page(pfn, vma_pagesize);
> + invalidate_icache_guest_page(pfnpg.pfn, vma_pagesize);

This is going to clash with what is currently in -next, specially with
MTE.

Paolo, if you really want to take this in 5.13, can you please push a
stable branch based on -rc4 or older so that I can merge it in and
test it?

Thanks,

M.

--
Without deviation from the norm, progress is not possible.