From patchwork Fri Dec 17 15:30:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jing Liu X-Patchwork-Id: 12685125 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 1BAA7C433FE for ; Fri, 17 Dec 2021 15:30:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238535AbhLQPat (ORCPT ); Fri, 17 Dec 2021 10:30:49 -0500 Received: from mga03.intel.com ([134.134.136.65]:10848 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238255AbhLQPaJ (ORCPT ); Fri, 17 Dec 2021 10:30:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1639755009; x=1671291009; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=U3csfgTLbEXdbK8cw/YgoQNoInbEKp5oorFH3mqVag0=; b=oGwZ21HUIzb6QiNHFVrFGfLUtMmpaZMtTgTTIyG1at0HfVWpNS7bclNN VZm04JyAES6hGci8JeHnH+b/SvQ4xH/SDwTYfZXvUcbCDKVeGZZqU2sBq DR7ZZHQjBml/+C6Dqg+T/LuF8snznbt71tGQn2mMYhgIJykC/0AjE13F4 S4hh21zKi3k9/3V47YO5Os+Nx3V0iYfRBXxV99mEs238FVtX0QpBINVES fTgKTRdrA6k4jWqOQaiSkfGkvwyoDHnJWrd6miWwugLV5GLndd1YiWx7A z3Zsr4p7DQ+ct4LG8yTYD3pPDL+YknrZAZuWWqvZzlsIcI+VB48vxt6SZ w==; X-IronPort-AV: E=McAfee;i="6200,9189,10200"; a="239723478" X-IronPort-AV: E=Sophos;i="5.88,213,1635231600"; d="scan'208";a="239723478" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Dec 2021 07:30:06 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,213,1635231600"; d="scan'208";a="615588478" Received: from 984fee00a228.jf.intel.com ([10.165.56.59]) by orsmga004.jf.intel.com with ESMTP; 17 Dec 2021 07:30:06 -0800 From: Jing Liu To: x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, pbonzini@redhat.com Cc: seanjc@google.com, jun.nakajima@intel.com, kevin.tian@intel.com, jing2.liu@linux.intel.com, jing2.liu@intel.com, guang.zeng@intel.com, wei.w.wang@intel.com, yang.zhong@intel.com Subject: [PATCH v2 22/23] kvm: x86: Disable interception for IA32_XFD on demand Date: Fri, 17 Dec 2021 07:30:02 -0800 Message-Id: <20211217153003.1719189-23-jing2.liu@intel.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20211217153003.1719189-1-jing2.liu@intel.com> References: <20211217153003.1719189-1-jing2.liu@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Always intercepting IA32_XFD causes non-negligible overhead when this register is updated frequently in the guest. Disable r/w emulation after intercepting the first WRMSR(IA32_XFD) with a non-zero value. Disable WRMSR emulation implies that IA32_XFD becomes out-of-sync with the software states in fpstate and the per-cpu xfd cache. Call fpu_sync_guest_vmexit_xfd_state() to bring them back in-sync, before preemption is enabled. p.s. We have confirmed that SDM is being revised to say that when setting IA32_XFD[18] the AMX register state is not guaranteed to be preserved. This clarification avoids adding mess for a creative guest which sets IA32_XFD[18]=1 before saving active AMX state to its own storage. Signed-off-by: Kevin Tian Signed-off-by: Yang Zhong Signed-off-by: Jing Liu --- arch/x86/include/asm/kvm-x86-ops.h | 1 + arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/vmx/vmx.c | 10 ++++++++++ arch/x86/kvm/vmx/vmx.h | 2 +- arch/x86/kvm/x86.c | 6 ++++++ 5 files changed, 20 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h index cefe1d81e2e8..60c27f9990e9 100644 --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -30,6 +30,7 @@ KVM_X86_OP(update_exception_bitmap) KVM_X86_OP(get_msr) KVM_X86_OP(set_msr) KVM_X86_OP(get_segment_base) +KVM_X86_OP_NULL(set_xfd_passthrough) KVM_X86_OP(get_segment) KVM_X86_OP(get_cpl) KVM_X86_OP(set_segment) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 860ed500580c..b513c12fa39e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -640,6 +640,7 @@ struct kvm_vcpu_arch { u64 smi_count; bool tpr_access_reporting; bool xsaves_enabled; + bool xfd_out_of_sync; u64 ia32_xss; u64 microcode_version; u64 arch_capabilities; @@ -1329,6 +1330,7 @@ struct kvm_x86_ops { void (*update_exception_bitmap)(struct kvm_vcpu *vcpu); int (*get_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr); int (*set_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr); + void (*set_xfd_passthrough)(struct kvm_vcpu *vcpu); u64 (*get_segment_base)(struct kvm_vcpu *vcpu, int seg); void (*get_segment)(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 483075045253..97a823a3f23f 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -162,6 +162,7 @@ static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = { MSR_FS_BASE, MSR_GS_BASE, MSR_KERNEL_GS_BASE, + MSR_IA32_XFD, #endif MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, @@ -1929,6 +1930,14 @@ static u64 vcpu_supported_debugctl(struct kvm_vcpu *vcpu) return debugctl; } +#ifdef CONFIG_X86_64 +static void vmx_set_xfd_passthrough(struct kvm_vcpu *vcpu) +{ + vmx_disable_intercept_for_msr(vcpu, MSR_IA32_XFD, MSR_TYPE_RW); + vcpu->arch.xfd_out_of_sync = true; +} +#endif + /* * Writes msr value into the appropriate "register". * Returns 0 on success, non-0 otherwise. @@ -7664,6 +7673,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = { #ifdef CONFIG_X86_64 .set_hv_timer = vmx_set_hv_timer, .cancel_hv_timer = vmx_cancel_hv_timer, + .set_xfd_passthrough = vmx_set_xfd_passthrough, #endif .setup_mce = vmx_setup_mce, diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 4df2ac24ffc1..bf9d3051cd6c 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -340,7 +340,7 @@ struct vcpu_vmx { struct lbr_desc lbr_desc; /* Save desired MSR intercept (read: pass-through) state */ -#define MAX_POSSIBLE_PASSTHROUGH_MSRS 13 +#define MAX_POSSIBLE_PASSTHROUGH_MSRS 14 struct { DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS); DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 796a9f2d1f23..13ba1e066b55 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3686,6 +3686,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) return 1; fpu_update_guest_xfd(&vcpu->arch.guest_fpu, data); + + if (data && kvm_x86_ops.set_xfd_passthrough) + static_call(kvm_x86_set_xfd_passthrough)(vcpu); break; case MSR_IA32_XFD_ERR: if (!msr_info->host_initiated && @@ -10023,6 +10026,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) if (vcpu->arch.guest_fpu.xfd_err) wrmsrl(MSR_IA32_XFD_ERR, 0); + if (vcpu->arch.xfd_out_of_sync) + fpu_sync_guest_vmexit_xfd_state(); + /* * Consume any pending interrupts, including the possible source of * VM-Exit on SVM and any ticks that occur between VM-Exit and now.