Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754662AbbKQTMt (ORCPT ); Tue, 17 Nov 2015 14:12:49 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:20892 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753387AbbKQTMq (ORCPT ); Tue, 17 Nov 2015 14:12:46 -0500 X-IronPort-AV: E=Sophos;i="5.20,309,1444694400"; d="scan'208";a="318739161" Message-ID: <564B7C2B.5030901@citrix.com> Date: Tue, 17 Nov 2015 19:12:43 +0000 From: Andrew Cooper User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Andy Lutomirski , Boris Ostrovsky CC: "linux-kernel@vger.kernel.org" , xen-devel , Borislav Petkov , David Vrabel , "H. Peter Anvin" Subject: Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit References: <1447456706-24347-1-git-send-email-boris.ostrovsky@oracle.com> <56468D24.8030801@oracle.com> <564A0371.2040104@oracle.com> <20151116195906.GB20137@pd.tnic> <20151116202232.GC20137@pd.tnic> <564A50C3.1000200@zytor.com> <564B3C57.5000002@oracle.com> In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1645 Lines: 44 On 17/11/15 18:49, Andy Lutomirski wrote: > On Nov 17, 2015 6:40 AM, "Boris Ostrovsky" wrote: >> On 11/16/2015 04:55 PM, H. Peter Anvin wrote: >>> On 11/16/15 12:22, Borislav Petkov wrote: >>>> Huh, so what's wrong with a jump: >>>> >>>> jmp 1f >>>> swapgs >>>> 1: >>>> >>> What is the point of that jump? >>> >>>>> If it would make you feel better, it could be X86_BUG_XENPV :-p >>>> That doesn't matter - I just don't want to open the flood gates on >>>> pseudo feature bits. >>>> >>>> hpa, what do you think? >>> Pseudo feature bits are fine, we already have plenty of them. They make >>> sense as they let us reuse a lot of infrastructure. >> >> >> So how about something like this? And then I think we can remove usergs_sysret32 and irq_enable_sysexit pv ops completely as noone will use them (lguest doesn't set them) >> > Looks good to me. Does Xen have any sysexit/sysret32 equivalent to > return to 32-bit user mode? If so, it could be worth trying to wire > it up by patching the jz instead of the test instruction. >From the guests point of view, there is only hypercall_iret. > > Also, I'd prefer X86_FEATURE_XENPV. IMO "PV" means too many things to > too many people. I agree - PV on its own is too generic. An alternative might be X86_FEATURE_XEN_PV_GUEST which is very clear an unambiguous, although rather longer. ~Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/