linux-kernel - [PATCH 4/6] KVM: SEV: WARN if SEV-ES is marked active but SEV is not

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Message-Id: <20211109215101.2211373-5-seanjc@google.com>
Date:   Tue,  9 Nov 2021 21:50:59 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Peter Gonda <pgonda@...gle.com>,
        Marc Orr <marcorr@...gle.com>,
        Nathan Tempelman <natet@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 4/6] KVM: SEV: WARN if SEV-ES is marked active but SEV is not

WARN if the VM is tagged as SEV-ES but not SEV.  KVM relies on SEV and
SEV-ES being set atomically, and guards common flows with "is SEV", i.e.
observing SEV-ES without SEV means KVM has a fatal bug.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 0d7bbe548ac3..a345f557be4a 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -242,7 +242,7 @@ static inline bool sev_es_guest(struct kvm *kvm)
 #ifdef CONFIG_KVM_AMD_SEV
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 
-	return sev_guest(kvm) && sev->es_active;
+	return sev->es_active && !WARN_ON_ONCE(!sev->active);
 #else
 	return false;
 #endif
-- 
2.34.0.rc0.344.g81b53c2807-goog