linux-kernel - Re: [PATCH v5 1/4] KVM: x86: Clarify the kvm_run.emulation

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Message-ID: <YUNu2npJv2LPBRop@google.com>
Date:   Thu, 16 Sep 2021 16:20:42 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     David Edmondson <dme@....org>
Cc:     linux-kernel@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jim Mattson <jmattson@...gle.com>,
        David Edmondson <david.edmondson@...cle.com>
Subject: Re: [PATCH v5 1/4] KVM: x86: Clarify the kvm_run.emulation_failure
 structure layout

On Thu, Sep 16, 2021, David Edmondson wrote:

For all these patches, assuming you want the Author credit to go to your @oracle.com
email, they need an explicit

  From: David Edmondson <david.edmondson@...cle.com>

otherwise git will default to the "From" email header and make the Author
"David Edmondson <dme@....org>".  And then checkpatch will rightly complain that
the SOB does not match the Author.

Adding From: can be handled automatically by "git format-patch" via "--from", e.g.

  git format-patch --from="David Edmondson <dme@....org>" ...

> Until more flags for kvm_run.emulation_failure flags are defined, it
> is undetermined whether new payload elements corresponding to those
> flags will be additive or alternative. As a hint to userspace that an
> alternative is possible, wrap the current payload elements in a union.
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: David Edmondson <david.edmondson@...cle.com>
> ---
>  include/uapi/linux/kvm.h | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index a067410ebea5..8618fe973215 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -402,8 +402,12 @@ struct kvm_run {
>  			__u32 suberror;
>  			__u32 ndata;
>  			__u64 flags;
> -			__u8  insn_size;
> -			__u8  insn_bytes[15];
> +			union {
> +				struct {
> +					__u8  insn_size;
> +					__u8  insn_bytes[15];
> +				};
> +			};
>  		} emulation_failure;
>  		/* KVM_EXIT_OSI */
>  		struct {
> -- 
> 2.33.0
>