linux-kernel - [PATCH 2/3] KVM: x86: Propagate AMD's IbrsSameMode to the guest

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Message-ID: <20250221163352.3818347-3-yosry.ahmed@linux.dev>
Date: Fri, 21 Feb 2025 16:33:51 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: x86@...nel.org,
	Sean Christopherson <seanjc@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Jim Mattson <jmattson@...gle.com>,
	"Kaplan, David" <David.Kaplan@....com>,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH 2/3] KVM: x86: Propagate AMD's IbrsSameMode to the guest

If IBRS provides same mode (kernel/user or host/guest) protection on the
host, then by definition it also provides same mode protection in the
guest. In fact, all different modes from the guest's perspective are the
same mode from the host's perspective anyway.

Propagate IbrsSameMode to the guests.

Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 arch/x86/kvm/cpuid.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index edef30359c198..05d7bbfbb8885 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1103,6 +1103,7 @@ void kvm_set_cpu_caps(void)
 		F(AMD_SSB_NO),
 		F(AMD_STIBP),
 		F(AMD_STIBP_ALWAYS_ON),
+		F(AMD_IBRS_SAME_MODE),
 		F(AMD_PSFD),
 		F(AMD_IBPB_RET),
 	);
-- 
2.48.1.601.g30ceb7b040-goog