linux-kernel - Re: [PATCH kernel v5 6/6] x86/sev: Do not handle #VC for DR7 read/write

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Message-ID: <ZGv+Y60qvbjeTY57@google.com>
Date:   Mon, 22 May 2023 16:44:35 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Alexey Kardashevskiy <aik@....com>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Pankaj Gupta <pankaj.gupta@....com>,
        Nikunj A Dadhania <nikunj@....com>,
        Santosh Shukla <santosh.shukla@....com>,
        Carlos Bilbao <carlos.bilbao@....com>
Subject: Re: [PATCH kernel v5 6/6] x86/sev: Do not handle #VC for DR7 read/write

On Tue, Apr 11, 2023, Alexey Kardashevskiy wrote:
> With MSR_AMD64_SEV_DEBUG_SWAP enabled, the guest is not expected to
> receive a #VC for reads or writes of DR7.
> 
> Update the SNP_FEATURES_PRESENT mask with MSR_AMD64_SNP_DEBUG_SWAP so
> an SNP guest doesn't gracefully terminate during SNP feature negotiation
> if MSR_AMD64_SEV_DEBUG_SWAP is enabled.
> 
> Since a guest is not expected to receive a #VC on DR7 accesses when
> MSR_AMD64_SEV_DEBUG_SWAP is enabled, return an error from the #VC
> handler in this situation.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@....com>
> Reviewed-by: Carlos Bilbao <carlos.bilbao@....com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> Reviewed-by: Pankaj Gupta <pankaj.gupta@....com>
> ---
> Changes:
> v4:
> * rebased on top of SNP feature negotiation
> 
> v2:
> * use new bit definition
> ---
>  arch/x86/boot/compressed/sev.c | 2 +-
>  arch/x86/kernel/sev.c          | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)

Can you post this separately (or bribe Boris to grab it)?  IIUC, this has no
dependency on the KVM enabling, i.e. can/should go through the tip tree without
waiting for the KVM patches to be applied.