From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [semi-urgent Xen CS question] Re: git commit 9fd67b4ed0714ab718f1f9bd14c344af336a6df7 (x86-64: Give vvars their own page) breaks Xen PV guests (64-bit). Date: Fri, 29 Jul 2011 08:31:35 -0700 Message-ID: <4E32D257.6090606@goop.org> References: <1093cd3a-acfe-49ab-b410-9fb49b139816@email.android.com> <4E30317E.30706@goop.org> <4E3048B4.6020805@goop.org> <4E30FCAE.4070906@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Andrew Lutomirski Cc: Keir Fraser , xen-devel@lists.xensource.com, Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org On 07/29/2011 05:51 AM, Andrew Lutomirski wrote: > VCGF_in_syscall: gettimeofday() (the syscall version) takes 593 ns. > Without VCGF_in_syscall, it's 712 ns. > > I'd argue for using my original approach of adding a user_64bit_mode > function -- I think it's a legitimate cleanup and Xen, for better or > worse, really does have two long mode CPL 3 selectors. If we removed > selector 6 from the GDT, that would be a different story, but that > would probably be a more intrusive change. Sigh. Yeah, let's see what happens. J