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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1DD5C77B73 for ; Thu, 27 Apr 2023 03:46:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242937AbjD0Dq0 (ORCPT ); Wed, 26 Apr 2023 23:46:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242825AbjD0DqQ (ORCPT ); Wed, 26 Apr 2023 23:46:16 -0400 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A5E0420E; Wed, 26 Apr 2023 20:46:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1682567175; x=1714103175; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=vxDIREfs/gWOTr6RZRuTNYwYFcISY67IkdEr84O8tCQ=; b=TC3r27VlFwBaIBn/KKWGomfmiSTab+7ZVyMkCtakCeVYs8JbChUoRA8/ VS6+unOVz0gcWFHm4picxktevtKE3vjC2kuHqYCaQhbq+S4hClzzyFn1v 7+H2jQXK5Tmo3SMTvywLibMX0vFSZYV1KE/rnlz0pXkrX0OyBFNH4iwmY VL2fH34Q0tRl221wtyIg2eYe55XyiWt09Uvyose26PVmcUKm66S626pl8 lpcTZiqrEJbmHryhyRSVEp+bxQjRE0xj/zxb69f2PtcHpgbMfldvfvSGJ 949paqPTWQA3V+Oe0iqCvic4/7dMSBSJGGRf8c+qS8PU+8yojlzFRhjbk w==; X-IronPort-AV: E=McAfee;i="6600,9927,10692"; a="326916673" X-IronPort-AV: E=Sophos;i="5.99,230,1677571200"; d="scan'208";a="326916673" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Apr 2023 20:46:14 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10692"; a="726856647" X-IronPort-AV: E=Sophos;i="5.99,230,1677571200"; d="scan'208";a="726856647" Received: from binbinwu-mobl.ccr.corp.intel.com (HELO [10.238.10.34]) ([10.238.10.34]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Apr 2023 20:46:12 -0700 Message-ID: Date: Thu, 27 Apr 2023 11:46:08 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2 09/21] KVM:x86: Load guest FPU state when accessing xsaves-managed MSRs To: Yang Weijiang , seanjc@google.com, pbonzini@redhat.com, peterz@infradead.org, john.allen@amd.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: rick.p.edgecombe@intel.com, Sean Christopherson References: <20230421134615.62539-1-weijiang.yang@intel.com> <20230421134615.62539-10-weijiang.yang@intel.com> From: Binbin Wu In-Reply-To: <20230421134615.62539-10-weijiang.yang@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 4/21/2023 9:46 PM, Yang Weijiang wrote: > From: Sean Christopherson > > Load the guest's FPU state if userspace is accessing MSRs whose values are > managed by XSAVES so that the MSR helpers, e.g. kvm_{get,set}_xsave_msr(), So far, kvm_{get,set}_xsave_msr() is not introduced yet. IMO, it is a bit confusing to understand the whole picture without the following patches. May be add some description or adjust the order? > can simply do {RD,WR}MSR to access the guest's value. > > If new feature MSRs supported in XSS are passed through to the guest they > are saved and restored by XSAVES/XRSTORS, i.e. in the guest's FPU state. > > Because is also used for the KVM_GET_MSRS device ioctl(), explicitly check > @vcpu is non-null before attempting to load guest state. The XSS supporting > MSRs cannot be retrieved via the device ioctl() without loading guest FPU > state (which doesn't exist). > > Note that guest_cpuid_has() is not queried as host userspace is allowed > to access MSRs that have not been exposed to the guest, e.g. it might do > KVM_SET_MSRS prior to KVM_SET_CPUID2. > > Signed-off-by: Sean Christopherson > Co-developed-by: Yang Weijiang > Signed-off-by: Yang Weijiang > --- > arch/x86/kvm/x86.c | 29 ++++++++++++++++++++++++++++- > 1 file changed, 28 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index d2975ca96ac5..7788646bbf1f 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -130,6 +130,9 @@ static int __set_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); > static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); > > static DEFINE_MUTEX(vendor_module_lock); > +static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu); > +static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu); > + > struct kvm_x86_ops kvm_x86_ops __read_mostly; > > #define KVM_X86_OP(func) \ > @@ -4336,6 +4339,21 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > } > EXPORT_SYMBOL_GPL(kvm_get_msr_common); > > +static const u32 xsave_msrs[] = { > + MSR_IA32_U_CET, MSR_IA32_PL3_SSP, > +}; > + > +static bool is_xsaves_msr(u32 index) > +{ > + int i; > + > + for (i = 0; i < ARRAY_SIZE(xsave_msrs); i++) { > + if (index == xsave_msrs[i]) > + return true; > + } > + return false; > +} > + > /* > * Read or write a bunch of msrs. All parameters are kernel addresses. > * > @@ -4346,11 +4364,20 @@ static int __msr_io(struct kvm_vcpu *vcpu, struct kvm_msrs *msrs, > int (*do_msr)(struct kvm_vcpu *vcpu, > unsigned index, u64 *data)) > { > + bool fpu_loaded = false; > int i; > > - for (i = 0; i < msrs->nmsrs; ++i) > + for (i = 0; i < msrs->nmsrs; ++i) { > + if (vcpu && !fpu_loaded && kvm_caps.supported_xss && > + is_xsaves_msr(entries[i].index)) { > + kvm_load_guest_fpu(vcpu); > + fpu_loaded = true; > + } > if (do_msr(vcpu, entries[i].index, &entries[i].data)) > break; > + } > + if (fpu_loaded) > + kvm_put_guest_fpu(vcpu); > > return i; > }