linux-kernel - Re: [PATCH 08/11] KVM: SVM: move guest vmsave/vmload back to assembly

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Message-ID: <Y2vHdMJiFrZNSJsB@google.com>
Date:   Wed, 9 Nov 2022 15:29:56 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        thomas.lendacky@....com, jmattson@...gle.com,
        stable@...r.kernel.org
Subject: Re: [PATCH 08/11] KVM: SVM: move guest vmsave/vmload back to assembly

On Wed, Nov 09, 2022, Paolo Bonzini wrote:
> FILL_RETURN_BUFFER can access percpu data, therefore vmload of the
> host save area must be executed first.  First of all, move the VMCB
> vmsave/vmload to assembly, essentially undoing commit fb0c4a4fee5a ("KVM:

Nit, similar to adding parantheses to function names, I prefer capitalizing instruction
mnemonics, i.e. VMSAVE and VMLOAD, to make it obvious that you're referring to a
specific instruction as opposed to a theme/flow.

> SVM: move VMLOAD/VMSAVE to C code", 2021-03-15).  The reason for that
> commit was that it made it simpler to use a different VMCB for
> VMLOAD/VMSAVE versus VMRUN; but that is not a big hassle anymore thanks
> to the kvm-asm-offsets machinery.
> 
> The idea on how to number the exception tables is stolen from
> a prototype patch by Peter Zijlstra.
> 
> Cc: stable@...r.kernel.org
> Fixes: a149180fbcf3 ("x86: Add magic AMD return-thunk")
> Link: <https://lore.kernel.org/all/f571e404-e625-bae1-10e9-449b2eb4cbd8@citrix.com/>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@...gle.com>