linux-kernel - [PATCH] KVM: x86: Set BHI_NO in guest when host is not affected by BHI

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Message-Id: <20240411072445.522731-1-alexandre.chartre@oracle.com>
Date: Thu, 11 Apr 2024 09:24:45 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: x86@...nel.org, kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, daniel.sneddon@...ux.intel.com,
        pawan.kumar.gupta@...ux.intel.com, tglx@...utronix.de,
        konrad.wilk@...cle.com, peterz@...radead.org,
        gregkh@...uxfoundation.org, seanjc@...gle.com,
        andrew.cooper3@...rix.com, dave.hansen@...ux.intel.com,
        nik.borisov@...e.com, kpsingh@...nel.org, longman@...hat.com,
        bp@...en8.de, pbonzini@...hat.com, alexandre.chartre@...cle.com
Subject: [PATCH] KVM: x86: Set BHI_NO in guest when host is not affected by BHI

When a system is not affected by the BHI bug then KVM should
configure guests with BHI_NO to ensure they won't enable any
BHI mitigation.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 984ea2089efc..f43d3c15a6b7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1678,6 +1678,9 @@ static u64 kvm_get_arch_capabilities(void)
 	if (!boot_cpu_has_bug(X86_BUG_GDS) || gds_ucode_mitigated())
 		data |= ARCH_CAP_GDS_NO;
 
+	if (!boot_cpu_has_bug(X86_BUG_BHI))
+		data |= ARCH_CAP_BHI_NO;
+
 	return data;
 }
 
-- 
2.39.3