linux-kernel - Re: [PATCH v1] AMD SSB bits.

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Date:   Tue, 5 Jun 2018 16:56:00 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org,
        tglx@...utronix.de, andrew.cooper3@...rix.com
Subject: Re: [PATCH v1] AMD SSB bits.

On Tue, Jun 05, 2018 at 08:23:13AM -0500, Tom Lendacky wrote:
> On 6/1/2018 9:59 AM, Konrad Rzeszutek Wilk wrote:
> > Hi,
> > 
> > I was reading the AMD whitepaper on SSBD and noticed that they have added
> > two new bits in the 8000_0008 CPUID. EBX:
> >  1) Bit[26] - similar to Intel's SSB_NO not needed anymore.
> >  2) Bit[24] - use SPEC_CTRL MSR (0x48) instead of VIRT SPEC_CTRL MSR
> >     (0xC001_011f).
> > 
> > See 124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
> > (A copy of this document is available at
> >     https://bugzilla.kernel.org/show_bug.cgi?id=199889)
> > 
> > Being that I don't have the hardware (not even sure if AMD has developed it yet)
> > I ended up cobbling up a DEBUG patch, the last one - which is well, debug
> > (see below).
> 
> So I'm not sure what is debug and what isn't, so I'm just commenting as if
> they weren't debug.  If this patch is just for debug, then you can
> probably ignore.

It is just for debugging.