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From:   Binbin Wu <binbin.wu@linux.intel.com>
To:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     seanjc@google.com, pbonzini@redhat.com, chao.gao@intel.com,
        kai.huang@intel.com, David.Laight@ACULAB.COM,
        robert.hu@linux.intel.com, guang.zeng@intel.com,
        binbin.wu@linux.intel.com
Subject: [PATCH v11 16/16] KVM: x86: Advertise LASS CPUID to user space
Date:   Wed, 13 Sep 2023 20:42:27 +0800
Message-Id: <20230913124227.12574-17-binbin.wu@linux.intel.com>
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From: Zeng Guang <guang.zeng@intel.com>

Linear address space separation (LASS) is an independent mechanism
to enforce the mode-based protection that can prevent user-mode
accesses to supervisor-mode addresses, and vice versa. Because the
LASS protections are applied before paging, malicious software can
not acquire any paging-based timing information to compromise the
security of system.

The CPUID bit definition to support LASS:
CPUID.(EAX=07H.ECX=1):EAX.LASS[bit 6]

Advertise LASS to user space to support LASS virtualization.

Note: KVM LASS feature exposure also depends on cpuid capability
held by host kernel. It will be masked to guest if host vsyscall
is in emulate mode which actually disables LASS.

Signed-off-by: Zeng Guang <guang.zeng@intel.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
---
 arch/x86/kvm/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index a0db266bab73..81a52218c20f 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -675,7 +675,7 @@ void kvm_set_cpu_caps(void)
 		kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD);
 
 	kvm_cpu_cap_mask(CPUID_7_1_EAX,
-		F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD) |
+		F(AVX_VNNI) | F(AVX512_BF16) | F(LASS) | F(CMPCCXADD) |
 		F(FZRM) | F(FSRS) | F(FSRC) |
 		F(AMX_FP16) | F(AVX_IFMA) | F(LAM)
 	);
-- 
2.25.1