linux-kernel - [PATCH 1/2] KVM: x86: Fixup "Get active PCID only when writing a CR3 value"

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Message-Id: <20210309021900.1001843-2-seanjc@google.com>
Date:   Mon,  8 Mar 2021 18:18:59 -0800
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,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 1/2] KVM: x86: Fixup "Get active PCID only when writing a CR3 value"

From: Sean Christopherson <sean.j.christopherson@...el.com>

Fix SME and PCID, which got horribly mangled on application.

Fixes: a16241ae56fa ("KVM: x86: Get active PCID only when writing a CR3 value")
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7876ddf896b8..271196400495 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3907,15 +3907,20 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
 	struct vcpu_svm *svm = to_svm(vcpu);
 	unsigned long cr3;
 
-	cr3 = __sme_set(root_hpa);
 	if (npt_enabled) {
-		svm->vmcb->control.nested_cr3 = root_hpa;
+		svm->vmcb->control.nested_cr3 = __sme_set(root_hpa);
 		vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
 
 		/* Loading L2's CR3 is handled by enter_svm_guest_mode.  */
 		if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
 			return;
 		cr3 = vcpu->arch.cr3;
+	} else if (vcpu->arch.mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
+		cr3 = __sme_set(root_hpa) | kvm_get_active_pcid(vcpu);
+	} else {
+		/* PCID in the guest should be impossible with a 32-bit MMU. */
+		WARN_ON_ONCE(kvm_get_active_pcid(vcpu));
+		cr3 = root_hpa;
 	}
 
 	svm->vmcb->save.cr3 = cr3;
-- 
2.30.1.766.gb4fecdf3b7-goog