linux-kernel - Re: [PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image

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Date:   Thu, 4 Jun 2020 13:54:13 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <jroedel@...e.de>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v3 40/75] x86/sev-es: Compile early handler code into
 kernel image

On Wed, May 20, 2020 at 11:14:15AM +0200, Borislav Petkov wrote:
> On Tue, Apr 28, 2020 at 05:16:50PM +0200, Joerg Roedel wrote:
> > +static inline u64 sev_es_rd_ghcb_msr(void)
> > +{
> > +	return native_read_msr(MSR_AMD64_SEV_ES_GHCB);
> > +}
> > +
> > +static inline void sev_es_wr_ghcb_msr(u64 val)
> > +{
> > +	u32 low, high;
> > +
> > +	low  = (u32)(val);
> > +	high = (u32)(val >> 32);
> > +
> > +	native_write_msr(MSR_AMD64_SEV_ES_GHCB, low, high);
> > +}
> 
> Instead of duplicating those two, you can lift the ones in the
> compressed image into sev-es.h and use them here. I don't care one bit
> about the MSR tracepoints in native_*_msr().

It is not only the trace-point, this would also eliminate exception
handling in case the MSR access triggers a #GP. The "Unhandled MSR
read/write" messages would turn into a "General Protection Fault"
message.


	Joerg