linux-kernel - Re: [PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests

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Date:	Wed, 18 Nov 2015 21:47:52 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests

On Wed, Nov 18, 2015 at 12:21:56PM -0800, Andy Lutomirski wrote:
> > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> > index e4f8010..0e4fe5b 100644
> > --- a/arch/x86/include/asm/cpufeature.h
> > +++ b/arch/x86/include/asm/cpufeature.h
> > @@ -216,6 +216,7 @@
> >  #define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause intercept */
> >  #define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter threshold */
> >  #define X86_FEATURE_VMMCALL     ( 8*32+15) /* Prefer vmmcall to vmcall */
> > +#define X86_FEATURE_XENPV       ( 8*32+16) /* Xen paravirtual guest */
> >
> 
> This bit is highly magical and I think we need Borislav's ack.

Yeah, that should be

#define X86_FEATURE_XENPV       ( 8*32+16) /* "" Xen paravirtual guest */
					      ^^

note the empty "". This prevents it from appearing in /proc/cpuinfo.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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