Re: [PATCH v3 04/13] KVM: x86: emulator: update the emulation mode after rsm

From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: kvm@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-kernel@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
	Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org, Jim Mattson <jmattson@google.com>,
	Kees Cook <keescook@chromium.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>, Joerg Roedel <joro@8bytes.org>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v3 04/13] KVM: x86: emulator: update the emulation mode after rsm
Date: Wed, 24 Aug 2022 21:50:43 +0000	[thread overview]
Message-ID: <YwadM2Y3FCMutSpt@google.com> (raw)
In-Reply-To: <20220803155011.43721-5-mlevitsk@redhat.com>

On Wed, Aug 03, 2022, Maxim Levitsky wrote:

Please make the changelog standalone, even though it means restating the shortlog
in most cases.  When viewing git commits, the shortlog+changelog are bundled
fairly close together, but when viewing patches in a mail client, e.g. when doing
initial review, the shortlog is in the subject which may be far away or even
completely hidden.

> This ensures that RIP will be correctly written back,
> because the RSM instruction can switch the CPU mode from
> 32 bit (or less) to 64 bit.

Wrap closer to ~75 chars.

> 
> This fixes a guest crash in case the #SMI is received
> while the guest runs a code from an address > 32 bit.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/emulate.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index bc70caf403c2b4..5e91b26cc1d8aa 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2666,6 +2666,11 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
>  	if (ret != X86EMUL_CONTINUE)
>  		goto emulate_shutdown;
>  
> +

Unnecessary newline.

> +	ret = emulator_recalc_and_set_mode(ctxt);
> +	if (ret != X86EMUL_CONTINUE)
> +		goto emulate_shutdown;
> +
>  	/*
>  	 * Note, the ctxt->ops callbacks are responsible for handling side
>  	 * effects when writing MSRs and CRs, e.g. MMU context resets, CPUID
> -- 
> 2.26.3
> 