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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 1D961C31E40 for ; Thu, 15 Aug 2019 06:30:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC7762086C for ; Thu, 15 Aug 2019 06:30:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730426AbfHOGaM (ORCPT ); Thu, 15 Aug 2019 02:30:12 -0400 Received: from ozlabs.org ([203.11.71.1]:37797 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729796AbfHOGaM (ORCPT ); Thu, 15 Aug 2019 02:30:12 -0400 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 468Glh3XBXz9sN1; Thu, 15 Aug 2019 16:30:08 +1000 (AEST) From: Michael Ellerman To: Thiago Jung Bauermann Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Alexey Kardashevskiy , Anshuman Khandual , Benjamin Herrenschmidt , Christoph Hellwig , Mike Anderson , Paul Mackerras , Ram Pai , Claudio Carvalho , Ryan Grimm Subject: Re: [PATCH v3 11/16] powerpc/pseries/svm: Export guest SVM status to user space via sysfs In-Reply-To: <87r25qgeb5.fsf@morokweng.localdomain> References: <20190806052237.12525-1-bauerman@linux.ibm.com> <20190806052237.12525-12-bauerman@linux.ibm.com> <8736i6sfhn.fsf@concordia.ellerman.id.au> <87r25qgeb5.fsf@morokweng.localdomain> Date: Thu, 15 Aug 2019 16:30:07 +1000 Message-ID: <87sgq36ivk.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thiago Jung Bauermann writes: > Michael Ellerman writes: >> Thiago Jung Bauermann writes: >>> From: Ryan Grimm >>> User space might want to know it's running in a secure VM. It can't do >>> a mfmsr because mfmsr is a privileged instruction. >>> >>> The solution here is to create a cpu attribute: >>> >>> /sys/devices/system/cpu/svm >>> >>> which will read 0 or 1 based on the S bit of the guest's CPU 0. >> >> Why CPU 0? >> >> If we have different CPUs running with different MSR_S then something >> has gone badly wrong, no? > > Yes, that would be very bad. > >> So can't we just read the MSR on whatever CPU the sysfs code happens to >> run on. > > Good point. I made the change in the patch below. The patch looks good. Although, it raises the question of whether it should be an attribute of the CPU at all. I guess there's not obviously anywhere better for it. Still you should document the attribute in Documentation/ABI/testing/sysfs-devices-system-cpu cheers > From 2d951305e118bf286f8e83cbf396448085186357 Mon Sep 17 00:00:00 2001 > From: Ryan Grimm > Date: Tue, 15 Jan 2019 11:56:29 -0600 > Subject: [PATCH] powerpc/pseries/svm: Export guest SVM status to user space > via sysfs > > User space might want to know it's running in a secure VM. It can't do > a mfmsr because mfmsr is a privileged instruction. > > The solution here is to create a cpu attribute: > > /sys/devices/system/cpu/svm > > which will read 0 or 1 based on the S bit of the current CPU. > > Signed-off-by: Ryan Grimm > Signed-off-by: Thiago Jung Bauermann > --- > arch/powerpc/kernel/sysfs.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > index e2147d7c9e72..80a676da11cb 100644 > --- a/arch/powerpc/kernel/sysfs.c > +++ b/arch/powerpc/kernel/sysfs.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > > #include "cacheinfo.h" > #include "setup.h" > @@ -715,6 +716,23 @@ static struct device_attribute pa6t_attrs[] = { > #endif /* HAS_PPC_PMC_PA6T */ > #endif /* HAS_PPC_PMC_CLASSIC */ > > +#ifdef CONFIG_PPC_SVM > +static ssize_t show_svm(struct device *dev, struct device_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%u\n", is_secure_guest()); > +} > +static DEVICE_ATTR(svm, 0444, show_svm, NULL); > + > +static void create_svm_file(void) > +{ > + device_create_file(cpu_subsys.dev_root, &dev_attr_svm); > +} > +#else > +static void create_svm_file(void) > +{ > +} > +#endif /* CONFIG_PPC_SVM */ > + > static int register_cpu_online(unsigned int cpu) > { > struct cpu *c = &per_cpu(cpu_devices, cpu); > @@ -1058,6 +1076,8 @@ static int __init topology_init(void) > sysfs_create_dscr_default(); > #endif /* CONFIG_PPC64 */ > > + create_svm_file(); > + > return 0; > } > subsys_initcall(topology_init);