From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Date: Thu, 19 Nov 2015 13:08:09 +0100 Message-ID: <20151119120809.GC5953@pd.tnic> References: <1447877179-2775-1-git-send-email-boris.ostrovsky@oracle.com> <1447877179-2775-2-git-send-email-boris.ostrovsky@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: 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: Andy Lutomirski Cc: Konrad Rzeszutek Wilk , "linux-kernel@vger.kernel.org" , Linux Virtualization , Ingo Molnar , David Vrabel , Andrew Lutomirski , "H. Peter Anvin" , "xen-devel@lists.xenproject.org" , Boris Ostrovsky , Thomas Gleixner List-Id: virtualization@lists.linuxfoundation.org T24gV2VkLCBOb3YgMTgsIDIwMTUgYXQgMTI6MjE6NTZQTSAtMDgwMCwgQW5keSBMdXRvbWlyc2tp IHdyb3RlOgo+IENvdWxkIHdlIG1ha2UgdGhpcyBhIGxpdHRsZSBsZXNzIHN1YnRsZToKPiAKPiBB TFRFUk5BVElWRSAidGVzdGwgJWVheCwgJWVheDsgbHogLkxzeXNjYWxsXzMyX2RvbmUiLCAiam1w Cj4gLkxzeXNjYXNsbF8zMl9kb25lIiwgWDg2X0ZFQVRVUkVfWEVOUFYKPiAKPiBCb3Jpc2xhdiwg d2hhdCBkbyB5b3UgdGhpbms/CgpJIGRvbid0IG1pbmQgZWl0aGVyLgoKSSB3b3VsZCd2ZSBzYWlk IHlvdXIgdmVyc2lvbiBkb2Vzbid0IHRvdWNoICVlYXggc28gdGhlIHJlc3VsdCBpbiB0aGVyZQpt aWdodCBiZSB1c2VmdWwgZm9yIGNhbGxlcnMgYnV0IGFsbCBwYXRocyBkbyBvdmVyd3JpdGUgaXQs IEFGQUlDVC4KCi0tIApSZWdhcmRzL0dydXNzLAogICAgQm9yaXMuCgpTVVNFIExpbnV4IEdtYkgs IEdGOiBGZWxpeCBJbWVuZMO2cmZmZXIsIEphbmUgU21pdGhhcmQsIEdyYWhhbSBOb3J0b24sIEhS QiAyMTI4NCAoQUcgTsO8cm5iZXJnKQotLSAKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX18KVmlydHVhbGl6YXRpb24gbWFpbGluZyBsaXN0ClZpcnR1YWxpemF0 aW9uQGxpc3RzLmxpbnV4LWZvdW5kYXRpb24ub3JnCmh0dHBzOi8vbGlzdHMubGludXhmb3VuZGF0 aW9uLm9yZy9tYWlsbWFuL2xpc3RpbmZvL3ZpcnR1YWxpemF0aW9u From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754905AbbKSMIY (ORCPT ); Thu, 19 Nov 2015 07:08:24 -0500 Received: from mx2.suse.de ([195.135.220.15]:47563 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750782AbbKSMIX (ORCPT ); Thu, 19 Nov 2015 07:08:23 -0500 Date: Thu, 19 Nov 2015 13:08:09 +0100 From: Borislav Petkov To: Andy Lutomirski Cc: Boris Ostrovsky , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , David Vrabel , Konrad Rzeszutek Wilk , Andrew Lutomirski , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xenproject.org" , Linux Virtualization Subject: Re: [PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Message-ID: <20151119120809.GC5953@pd.tnic> References: <1447877179-2775-1-git-send-email-boris.ostrovsky@oracle.com> <1447877179-2775-2-git-send-email-boris.ostrovsky@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 18, 2015 at 12:21:56PM -0800, Andy Lutomirski wrote: > Could we make this a little less subtle: > > ALTERNATIVE "testl %eax, %eax; lz .Lsyscall_32_done", "jmp > .Lsyscasll_32_done", X86_FEATURE_XENPV > > Borislav, what do you think? I don't mind either. I would've said your version doesn't touch %eax so the result in there might be useful for callers but all paths do overwrite it, AFAICT. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --