linux-kernel - Re: [PATCH] KVM: x86: Fix device passthrough when SME is active

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Message-ID: <8937db5e-4c8e-57cf-4059-d9e10ea1a393@amd.com>
Date:   Thu, 15 Mar 2018 23:03:09 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Brijesh Singh <brijesh.singh@....com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] KVM: x86: Fix device passthrough when SME is active

On 3/8/2018 5:17 PM, Tom Lendacky wrote:
> When using device passthrough with SME active, the MMIO range that is
> mapped for the device should not be mapped encrypted.  Add a check in
> set_spte() to insure that a page is not mapped encrypted if that page
> is a device MMIO page as indicated by kvm_is_mmio_pfn().
> 
> Cc: <stable@...r.kernel.org> # 4.14.x-
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>

Any concerns with this fix?

Thanks,
Tom

> ---
>  arch/x86/kvm/mmu.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index f551962..763bb3b 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2770,8 +2770,10 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  	else
>  		pte_access &= ~ACC_WRITE_MASK;
>  
> +	if (!kvm_is_mmio_pfn(pfn))
> +		spte |= shadow_me_mask;
> +
>  	spte |= (u64)pfn << PAGE_SHIFT;
> -	spte |= shadow_me_mask;
>  
>  	if (pte_access & ACC_WRITE_MASK) {
>  
>