linux-kernel - [PATCH] kvm/svm: PKU not currently supported

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Message-Id: <20191219152332.28857-1-john.allen@amd.com>
Date:   Thu, 19 Dec 2019 09:23:32 -0600
From:   John Allen <john.allen@....com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, pbonzini@...hat.com,
        rkrcmar@...hat.com, John Allen <john.allen@....com>
Subject: [PATCH] kvm/svm: PKU not currently supported

Current SVM implementation does not have support for handling PKU. Guests
running on a host with future AMD cpus that support the feature will read
garbage from the PKRU register and will hit segmentation faults on boot as
memory is getting marked as protected that should not be. Ensure that cpuid
from SVM does not advertise the feature.

Signed-off-by: John Allen <john.allen@....com>
---
 arch/x86/kvm/svm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 122d4ce3b1ab..f911aa1b41c8 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5933,6 +5933,8 @@ static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
 		if (avic)
 			entry->ecx &= ~bit(X86_FEATURE_X2APIC);
 		break;
+	case 0x7:
+		entry->ecx &= ~bit(X86_FEATURE_PKU);
 	case 0x80000001:
 		if (nested)
 			entry->ecx |= (1 << 2); /* Set SVM bit */
-- 
2.24.0