Re: [PATCH] KVM: MMU: Segregate mmu pages created with different cr4.pge settings

From: Alexander Graf <agraf@suse.de>
To: Avi Kivity <avi@redhat.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>, joerg.roedel@amd.com
Subject: Re: [PATCH] KVM: MMU: Segregate mmu pages created with different cr4.pge	settings
Date: Mon, 05 Jan 2009 15:56:41 +0100	[thread overview]
Message-ID: <49621FA9.5080903@suse.de> (raw)
In-Reply-To: <20081221184146.8E00B250012@cleopatra.tlv.redhat.com>

Avi Kivity wrote:
> From: Avi Kivity <avi@redhat.com>
>
> Don't allow a vcpu with cr4.pge cleared to use a shadow page created with
> cr4.pge set; this might cause a cr3 switch not to sync ptes that have the
> global bit set (the global bit has no effect if !cr4.pge).
>
> This can only occur on smp with different cr4.pge settings for different
> vcpus (since a cr4 change will resync the shadow ptes), but there's no
> cost to being correct here.
>
> Signed-off-by: Avi Kivity <avi@redhat.com>
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index f49bfd0..ab8ef1d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -183,6 +183,7 @@ union kvm_mmu_page_role {
>  		unsigned metaphysical:1;
>  		unsigned access:3;
>  		unsigned invalid:1;
> +		unsigned cr4_pge:1;
>  	};
>  };
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c4da7fb..aa4575c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -363,6 +363,7 @@ void kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
>  	}
>  	kvm_x86_ops->set_cr4(vcpu, cr4);
>  	vcpu->arch.cr4 = cr4;
> +	vcpu->arch.mmu.base_role.cr4_pge = !!(cr4 & X86_CR4_PGE);
>   

This line broke VMware ESX bootup using NPT on one VCPU for me. If I
comment it out and apply my patches to actually make ESX run, it boots
again.

Alex

>  	kvm_mmu_sync_global(vcpu);
>  	kvm_mmu_reset_context(vcpu);
>  }
> --
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