From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5147AC433E0 for ; Mon, 29 Jun 2020 19:32:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A9B52067D for ; Mon, 29 Jun 2020 19:32:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730090AbgF2Tb6 (ORCPT ); Mon, 29 Jun 2020 15:31:58 -0400 Received: from mx2.suse.de ([195.135.220.15]:36734 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732448AbgF2Tb2 (ORCPT ); Mon, 29 Jun 2020 15:31:28 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 326E3AD76; Mon, 29 Jun 2020 05:17:22 +0000 (UTC) Subject: Re: [PATCH fsgsbase v2 4/4] x86/fsgsbase: Fix Xen PV support To: Andy Lutomirski , x86@kernel.org Cc: Sasha Levin , linux-kernel@vger.kernel.org, Andrew Cooper , Boris Ostrovsky , Stefano Stabellini , xen-devel@lists.xenproject.org References: From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <714d4c04-5907-885f-e23b-baef662f1080@suse.com> Date: Mon, 29 Jun 2020 07:17:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.06.20 19:24, Andy Lutomirski wrote: > On Xen PV, SWAPGS doesn't work. Teach __rdfsbase_inactive() and > __wrgsbase_inactive() to use rdmsrl()/wrmsrl() on Xen PV. The Xen > pvop code will understand this and issue the correct hypercalls. > > Cc: Boris Ostrovsky > Cc: Juergen Gross > Cc: Stefano Stabellini > Cc: xen-devel@lists.xenproject.org > Signed-off-by: Andy Lutomirski > --- > arch/x86/kernel/process_64.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c > index cb8e37d3acaa..457d02aa10d8 100644 > --- a/arch/x86/kernel/process_64.c > +++ b/arch/x86/kernel/process_64.c > @@ -163,9 +163,13 @@ static noinstr unsigned long __rdgsbase_inactive(void) > > lockdep_assert_irqs_disabled(); > > - native_swapgs(); > - gsbase = rdgsbase(); > - native_swapgs(); > + if (!static_cpu_has(X86_FEATURE_XENPV)) { > + native_swapgs(); > + gsbase = rdgsbase(); > + native_swapgs(); > + } else { > + rdmsrl(MSR_KERNEL_GS_BASE, gsbase); > + } > > return gsbase; > } > @@ -182,9 +186,13 @@ static noinstr void __wrgsbase_inactive(unsigned long gsbase) > { > lockdep_assert_irqs_disabled(); > > - native_swapgs(); > - wrgsbase(gsbase); > - native_swapgs(); > + if (!static_cpu_has(X86_FEATURE_XENPV)) { > + native_swapgs(); > + wrgsbase(gsbase); > + native_swapgs(); > + } else { > + wrmsrl(MSR_KERNEL_GS_BASE, gsbase); > + } > } > > /* > Another possibility would be to just do (I'm fine either way): diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index acc49fa6a097..b78dd373adbf 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -318,6 +318,8 @@ static void __init xen_init_capabilities(void) setup_clear_cpu_cap(X86_FEATURE_XSAVE); setup_clear_cpu_cap(X86_FEATURE_OSXSAVE); } + + setup_clear_cpu_cap(X86_FEATURE_FSGSBASE); } static void xen_set_debugreg(int reg, unsigned long val) Juergen