linux-kernel - [PATCH 5.11 573/601] KVM: SVM: Disable SEV/SEV-ES if NPT is disabled

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Message-Id: <20210512144846.717365824@linuxfoundation.org>
Date:   Wed, 12 May 2021 16:50:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tom Lendacky <thomas.lendacky@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 573/601] KVM: SVM: Disable SEV/SEV-ES if NPT is disabled

From: Sean Christopherson <seanjc@...gle.com>

[ Upstream commit fa13680f5668cff05302a2f4753c49334a83a064 ]

Disable SEV and SEV-ES if NPT is disabled.  While the APM doesn't clearly
state that NPT is mandatory, it's alluded to by:

  The guest page tables, managed by the guest, may mark data memory pages
  as either private or shared, thus allowing selected pages to be shared
  outside the guest.

And practically speaking, shadow paging can't work since KVM can't read
the guest's page tables.

Fixes: e9df09428996 ("KVM: SVM: Add sev module_param")
Cc: Brijesh Singh <brijesh.singh@....com
Cc: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Message-Id: <20210422021125.3417167-4-seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/svm/svm.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 99592e03658b..15a69500819d 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -980,7 +980,16 @@ static __init int svm_hardware_setup(void)
 		kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE);
 	}
 
-	if (IS_ENABLED(CONFIG_KVM_AMD_SEV) && sev) {
+	if (!boot_cpu_has(X86_FEATURE_NPT))
+		npt_enabled = false;
+
+	if (npt_enabled && !npt)
+		npt_enabled = false;
+
+	kvm_configure_mmu(npt_enabled, get_max_npt_level(), PG_LEVEL_1G);
+	pr_info("kvm: Nested Paging %sabled\n", npt_enabled ? "en" : "dis");
+
+	if (IS_ENABLED(CONFIG_KVM_AMD_SEV) && sev && npt_enabled) {
 		sev_hardware_setup();
 	} else {
 		sev = false;
@@ -995,15 +1004,6 @@ static __init int svm_hardware_setup(void)
 			goto err;
 	}
 
-	if (!boot_cpu_has(X86_FEATURE_NPT))
-		npt_enabled = false;
-
-	if (npt_enabled && !npt)
-		npt_enabled = false;
-
-	kvm_configure_mmu(npt_enabled, get_max_npt_level(), PG_LEVEL_1G);
-	pr_info("kvm: Nested Paging %sabled\n", npt_enabled ? "en" : "dis");
-
 	if (nrips) {
 		if (!boot_cpu_has(X86_FEATURE_NRIPS))
 			nrips = false;
-- 
2.30.2