Re: [PATCH 1/5] mmu: mark spte present if the x bit is set

Paolo Bonzini
2016-06-28T08:44:53Z

On 28/06/2016 06:32, Bandan Das wrote:
> This is safe because is_shadow_present_pte() is called
> on host controlled page table and we know the spte is
> valid
>
> Signed-off-by: Bandan Das <bsd@redhat.com>
> ---
> arch/x86/kvm/mmu.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index def97b3..a50af79 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -304,7 +304,8 @@ static int is_nx(struct kvm_vcpu *vcpu)
>
> static int is_shadow_present_pte(u64 pte)
> {
> - return pte & PT_PRESENT_MASK && !is_mmio_spte(pte);
> + return pte & (PT_PRESENT_MASK | shadow_x_mask) &&
> + !is_mmio_spte(pte);

This should really be pte & 7 when using EPT. But this is okay as an
alternative to a new shadow_present_mask.

Paolo

> }
>
> static int is_large_pte(u64 pte)
>