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SubjectRe: [PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM
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On 08/01/20 01:12, Sean Christopherson wrote:
> Remove the bogus 64-bit only condition from the check that disables MMIO
> spte optimization when the system supports the max PA, i.e. doesn't have
> any reserved PA bits. 32-bit KVM always uses PAE paging for the shadow
> MMU, and per Intel's SDM:
>
> PAE paging translates 32-bit linear addresses to 52-bit physical
> addresses.
>
> The kernel's restrictions on max physical addresses are limits on how
> much memory the kernel can reasonably use, not what physical addresses
> are supported by hardware.
>
> Fixes: ce88decffd17 ("KVM: MMU: mmio page fault support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 7269130ea5e2..d9c07343d979 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6191,7 +6191,7 @@ static void kvm_set_mmio_spte_mask(void)
> * If reserved bit is not supported, clear the present bit to disable
> * mmio page fault.
> */
> - if (IS_ENABLED(CONFIG_X86_64) && shadow_phys_bits == 52)
> + if (shadow_phys_bits == 52)
> mask &= ~1ull;
>
> kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);
>

Queued, thanks.

Paolo

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