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From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 01/11] KVM: nVMX: Check PAUSE_EXITING, not BUS_LOCK_DETECTION, on PAUSE emulation
Date: Fri, 31 Jan 2025 17:55:08 -0800	[thread overview]
Message-ID: <20250201015518.689704-2-seanjc@google.com> (raw)
In-Reply-To: <20250201015518.689704-1-seanjc@google.com>

When emulating PAUSE on behalf of L2, check for interception in vmcs12 by
looking at primary execution controls, not secondary execution controls.
Checking for PAUSE_EXITING in secondary execution controls effectively
results in KVM looking for BUS_LOCK_DETECTION, which KVM doesn't expose to
L1, i.e. is always off in vmcs12, and ultimately results in KVM failing to
"intercept" PAUSE.

Because KVM doesn't handle interception during emulation correctly on VMX,
i.e. the "fixed" code is still quite broken, and not intercepting PAUSE is
relatively benign, for all intents and purposes the bug means that L2 gets
to live when it would otherwise get an unexpected #UD.

Fixes: 4984563823f0 ("KVM: nVMX: Emulate NOPs in L2, and PAUSE if it's not intercepted")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f72835e85b6d..3654c08cfa31 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8092,7 +8092,7 @@ int vmx_check_intercept(struct kvm_vcpu *vcpu,
 		 * the PAUSE.
 		 */
 		if ((info->rep_prefix != REPE_PREFIX) ||
-		    !nested_cpu_has2(vmcs12, CPU_BASED_PAUSE_EXITING))
+		    !nested_cpu_has(vmcs12, CPU_BASED_PAUSE_EXITING))
 			return X86EMUL_CONTINUE;
 
 		break;
-- 
2.48.1.362.g079036d154-goog


  reply	other threads:[~2025-02-01  1:55 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-01  1:55 [PATCH v2 00/11] KVM: x86: Fix emulation of (some) L2 instructions Sean Christopherson
2025-02-01  1:55 ` Sean Christopherson [this message]
2025-02-01  1:55 ` [PATCH v2 02/11] KVM: nSVM: Pass next RIP, not current RIP, for nested VM-Exit on emulation Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 03/11] KVM: nVMX: Allow emulating RDPID on behalf of L2 Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 04/11] KVM: nVMX: Emulate HLT in L2 if it's not intercepted Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 05/11] KVM: nVMX: Consolidate missing X86EMUL_INTERCEPTED logic in L2 emulation Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 06/11] KVM: x86: Plumb the src/dst operand types through to .check_intercept() Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 07/11] KVM: x86: Plumb the emulator's starting RIP into nested intercept checks Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 08/11] KVM: x86: Add a #define for the architectural max instruction length Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 09/11] KVM: nVMX: Allow the caller to provide instruction length on nested VM-Exit Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 10/11] KVM: nVMX: Synthesize nested VM-Exit for supported emulation intercepts Sean Christopherson
2025-02-01  1:55 ` [PATCH v2 11/11] KVM: selftests: Add a nested (forced) emulation intercept test for x86 Sean Christopherson
2025-02-28 17:06 ` [PATCH v2 00/11] KVM: x86: Fix emulation of (some) L2 instructions Sean Christopherson

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