linux-kernel - Re: [PATCH V2] x86/sev-es: Fix SEV-ES #VC handler for string port IO

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Message-ID: <4f71f9a4-3d78-a876-6fab-25549756fd2e@google.com>
Date:   Mon, 11 Jan 2021 10:55:49 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Tom Lendacky <thomas.lendacky@....com>
cc:     "Hyunwook (Wooky) Baek" <baekhw@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Joerg Roedel <jroedel@...e.de>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH V2] x86/sev-es: Fix SEV-ES #VC handler for string port
 IO

On Mon, 11 Jan 2021, Tom Lendacky wrote:

> > Don't assume dest/source buffers are userspace addresses when manually
> > copying data for string I/O or MOVS MMIO, as {get,put}_user() will fail
> > if handed a kernel address and ultimately lead to a kernel panic.
> > 
> > Signed-off-by: Hyunwook (Wooky) Baek <baekhw@...gle.com>
> > Acked-by: David Rientjes <rientjes@...gle.com>
> > ---
> > 
> > This patch is tested by invoking INSB/OUTSB instructions in kernel space in
> > a
> > SEV-ES-enabled VM. Without the patch, the kernel crashed with the following
> > message:
> >    "SEV-ES: Unsupported exception in #VC instruction emulation - can't
> > continue"
> > With the patch, the instructions successfully read/wrote the string from/to
> > the I/O port.
> 
> Shouldn't this have a Fixes: tag?
> 

Makes sense, I think this should likely be:

Fixes: f980f9c31a92 ("x86/sev-es: Compile early handler code into kernel image")