Re: [PATCH] KVM: MMU: Fix regression with ept memory types merged into non-ept page tables

[Joerg Roedel <joro@8bytes.org>]

On Mon, Sep 13, 2010 at 04:56:19PM +0200, Avi Kivity wrote:
> Commit "KVM: MMU: Make tdp_enabled a mmu-context parameter" made real-mode
> set ->direct_map, and changed the code that merges in the memory type depend
> on direct_map instead of tdp_enabled.  However, in this case what really
> matters is tdp, not direct_map, since tdp changes the pte format regardless
> of whether the mapping is direct or not.
> 
> As a result, real-mode shadow mappings got corrupted with ept memory types.
> The result was a huge slowdown, likely due to the cache being disabled.
> 
> Change it back as the simplest fix for the regression (real fix is to move
> all that to vmx code, and not use tdp_enabled as a synonym for ept).
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/mmu.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 6e248d8..3ce56bf 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1980,7 +1980,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  		spte |= shadow_user_mask;
>  	if (level > PT_PAGE_TABLE_LEVEL)
>  		spte |= PT_PAGE_SIZE_MASK;
> -	if (vcpu->arch.mmu.direct_map)
> +	if (tdp_enabled)
>  		spte |= kvm_x86_ops->get_mt_mask(vcpu, gfn,
>  			kvm_is_mmio_pfn(pfn));

Oh, indeed. Thanks for fixing this.

Acked-by: Joerg Roedel <joerg.roedel@amd.com>