Received-SPF: pass (google.com: domain of linux-kernel+bounces-36332-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
From: Yang Weijiang <weijiang.yang@intel.com>
To: seanjc@google.com,
	pbonzini@redhat.com,
	dave.hansen@intel.com,
	kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	x86@kernel.org,
	yuan.yao@linux.intel.com
Cc: peterz@infradead.org,
	chao.gao@intel.com,
	rick.p.edgecombe@intel.com,
	mlevitsk@redhat.com,
	john.allen@amd.com,
	weijiang.yang@intel.com
Subject: [PATCH v9 12/27] KVM: x86: Report XSS as to-be-saved if there are supported features
Date: Tue, 23 Jan 2024 18:41:45 -0800
Message-Id: <20240124024200.102792-13-weijiang.yang@intel.com>
In-Reply-To: <20240124024200.102792-1-weijiang.yang@intel.com>
References: <20240124024200.102792-1-weijiang.yang@intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

From: Sean Christopherson <seanjc@google.com>

Add MSR_IA32_XSS to list of MSRs reported to userspace if supported_xss
is non-zero, i.e. KVM supports at least one XSS based feature.

Before enabling CET virtualization series, guest IA32_MSR_XSS is
guaranteed to be 0, i.e., XSAVES/XRSTORS is executed in non-root mode
with XSS == 0, which equals to the effect of XSAVE/XRSTOR.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/x86.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 594c9e025f95..b3a39886e418 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1464,6 +1464,7 @@ static const u32 msrs_to_save_base[] = {
 	MSR_IA32_UMWAIT_CONTROL,
 
 	MSR_IA32_XFD, MSR_IA32_XFD_ERR,
+	MSR_IA32_XSS,
 };
 
 static const u32 msrs_to_save_pmu[] = {
@@ -7374,6 +7375,10 @@ static void kvm_probe_msr_to_save(u32 msr_index)
 		if (!(kvm_get_arch_capabilities() & ARCH_CAP_TSX_CTRL_MSR))
 			return;
 		break;
+	case MSR_IA32_XSS:
+		if (!kvm_caps.supported_xss)
+			return;
+		break;
 	default:
 		break;
 	}
-- 
2.39.3