From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [patch 12/17] Consistently wrap paravirt ops callsites to make them patchable Date: Mon, 2 Apr 2007 09:11:50 +0200 Message-ID: <200704020911.50623.ak@suse.de> References: <20070402055652.610711908@goop.org> <20070402055705.090656820@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20070402055705.090656820@goop.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jeremy Fitzhardinge Cc: virtualization@lists.osdl.org, Anthony Liguori , Andrew Morton , lkml List-Id: virtualization@lists.linuxfoundation.org On Monday 02 April 2007 07:57, Jeremy Fitzhardinge wrote: > Wrap a set of interesting paravirt_ops calls in a wrapper which makes > the callsites available for patching. Unfortunately this is pretty > ugly because there's no way to get gcc to generate a function call, > but also wrap just the callsite itself with the necessary labels. > = > This patch supports functions with 0-4 arguments, and either void or > returning a value. 64-bit arguments must be split into a pair of > 32-bit arguments (lower word first). Small structures are returned in > registers. Can you please add some comments to the code explaining this a little? Best would be perhaps a overview document in Documentation too. > +#define PVOP_CALL0(__rettype, __op) \ The __s shouldn't be needed for the macro arguments because there is no shared name space with the caller. > + ({ \ > + __rettype __ret; \ > + if (sizeof(__rettype) > sizeof(unsigned long)) { \ > + unsigned long long __tmp; \ > + unsigned long __ecx; \ > + asm volatile(paravirt_alt(PARAVIRT_CALL) \ Not having the volatile would probably generate better code, but it = seems much safer for now. > + : "=3DA" (__tmp), "=3Dc" (__ecx) \ > + : paravirt_type(__op), \ > + paravirt_clobber(CLBR_ANY) \ > + : "memory", "cc"); \ And the cc clobber is also not needed -Andi