linux-kernel - [PATCH v6 10/17] KVM: x86: nSVM: always intercept x2apic msrs

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Date:   Thu, 19 May 2022 05:27:02 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
CC:     <pbonzini@...hat.com>, <mlevitsk@...hat.com>, <seanjc@...gle.com>,
        <joro@...tes.org>, <jon.grimm@....com>, <wei.huang2@....com>,
        <terry.bowman@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v6 10/17] KVM: x86: nSVM: always intercept x2apic msrs

From: Maxim Levitsky <mlevitsk@...hat.com>

As a preparation for x2avic, this patch ensures that x2apic msrs
are always intercepted for the nested guest.

Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 5 +++++
 arch/x86/kvm/svm/svm.h    | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index f209c1ca540c..b61f8939c210 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -230,6 +230,11 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
 			break;
 
 		p      = msrpm_offsets[i];
+
+		/* x2apic msrs are intercepted always for the nested guest */
+		if (is_x2apic_msrpm_offset(p))
+			continue;
+
 		offset = svm->nested.ctl.msrpm_base_pa + (p * 4);
 
 		if (kvm_vcpu_read_guest(&svm->vcpu, offset, &value, 4))
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 16f1d117c98b..7e53474c8834 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -517,6 +517,15 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
 	return svm->nested.ctl.nested_ctl & SVM_NESTED_CTL_NP_ENABLE;
 }
 
+static inline bool is_x2apic_msrpm_offset(u32 offset)
+{
+	/* 4 msrs per u8, and 4 u8 in u32 */
+	u32 msr = offset * 16;
+
+	return (msr >= APIC_BASE_MSR) &&
+	       (msr < (APIC_BASE_MSR + 0x100));
+}
+
 /* svm.c */
 #define MSR_INVALID				0xffffffffU
 
-- 
2.25.1