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

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Message-ID: <564CF623.40502@oracle.com>
Date:	Wed, 18 Nov 2015 17:05:23 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Brian Gerst <brgerst@...il.com>
Cc:	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>,
	Borislav Petkov <bp@...e.de>,
	"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 11/18/2015 03:58 PM, Andy Lutomirski wrote:
> On Wed, Nov 18, 2015 at 12:50 PM, Brian Gerst <brgerst@...il.com> wrote:
>>
>> Can you just add !xen_pv_domain() to the opportunistic SYSRET check
>> instead?  Bury the alternatives in that macro, ie.
>> static_cpu_has(X86_FEATURE_XENPV).  That would likely benefit other
>> code as well.
> We could, but that won't help the 64-bit case where we want to keep
> the full asm path.

I don't think I understand what you mean here. Which full asm path?

-boris


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