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

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Message-ID: <20230816081942.GBZNyGnk/K+nDuBzsC@fat_crate.local>
Date:   Wed, 16 Aug 2023 10:19:42 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Alexey Kardashevskiy <aik@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Carlos Bilbao <carlos.bilbao@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Pankaj Gupta <pankaj.gupta@....com>
Subject: Re: [PATCH kernel v5] x86/sev: Do not handle #VC for DR7 read/write

On Wed, Aug 16, 2023 at 12:21:22PM +1000, 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>
> ---
> 
> The KVM part of DebugSwap went to kvm-x86 tree:
> https://lore.kernel.org/all/169058576410.1024559.1052772292093755719.b4-ty@google.com/
> but it is been suggested that this one can go via TIP:
> https://lore.kernel.org/all/ZGv+Y60qvbjeTY57@google.com/
> I am trying to bribe now by reviewing patches (internally), does this
> work? :) Thanks,

Oh yeah, most definitely! Anyone can bribe me when helping out with
review.

I very much appreciate people helping out with review so thanks!

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette