From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests
Date: Wed, 18 Nov 2015 17:05:23 -0500
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To: Andy Lutomirski <luto@amacapital.net>, Brian Gerst <brgerst@gmail.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Linux Virtualization <virtualization@lists.linux-foundation.org>, Ingo Molnar <mingo@redhat.com>, David Vrabel <david.vrabel@citrix.com>, Andrew Lutomirski <luto@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>, Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@suse.de>
List-Id: virtualization@lists.linuxfoundation.org

On 11/18/2015 03:58 PM, Andy Lutomirski wrote:
> On Wed, Nov 18, 2015 at 12:50 PM, Brian Gerst <brgerst@gmail.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