linux-kernel - [PATCH v2 03/12] KVM: SVM: Detect X2APIC virtualization (x2AVIC) support

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Date:   Tue, 12 Apr 2022 06:58:13 -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 v2 03/12] KVM: SVM: Detect X2APIC virtualization (x2AVIC) support

Add CPUID check for the x2APIC virtualization (x2AVIC) feature.
If available, the SVM driver can support both AVIC and x2AVIC modes
when load the kvm_amd driver with avic=1. The operating mode will be
determined at runtime depending on the guest APIC mode.

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/include/asm/svm.h |  3 +++
 arch/x86/kvm/svm/avic.c    | 34 ++++++++++++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c     |  8 ++------
 arch/x86/kvm/svm/svm.h     |  1 +
 4 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index f70a5108d464..2c2a104b777e 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -195,6 +195,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 #define AVIC_ENABLE_SHIFT 31
 #define AVIC_ENABLE_MASK (1 << AVIC_ENABLE_SHIFT)
 
+#define X2APIC_MODE_SHIFT 30
+#define X2APIC_MODE_MASK (1 << X2APIC_MODE_SHIFT)
+
 #define LBR_CTL_ENABLE_MASK BIT_ULL(0)
 #define VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK BIT_ULL(1)
 
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 655a7d20f8ee..fefac51063d3 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -40,6 +40,12 @@
 #define AVIC_GATAG_TO_VMID(x)		((x >> AVIC_VCPU_ID_BITS) & AVIC_VM_ID_MASK)
 #define AVIC_GATAG_TO_VCPUID(x)		(x & AVIC_VCPU_ID_MASK)
 
+enum avic_modes {
+	AVIC_MODE_NONE = 0,
+	AVIC_MODE_X1,
+	AVIC_MODE_X2,
+};
+
 /* Note:
  * This hash table is used to map VM_ID to a struct kvm_svm,
  * when handling AMD IOMMU GALOG notification to schedule in
@@ -50,6 +56,7 @@ static DEFINE_HASHTABLE(svm_vm_data_hash, SVM_VM_DATA_HASH_BITS);
 static u32 next_vm_id = 0;
 static bool next_vm_id_wrapped = 0;
 static DEFINE_SPINLOCK(svm_vm_data_hash_lock);
+static enum avic_modes avic_mode;
 
 /*
  * This is a wrapper of struct amd_iommu_ir_data.
@@ -1004,3 +1011,30 @@ void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)
 
 	avic_vcpu_load(vcpu);
 }
+
+/*
+ * Note:
+ * - The module param avic enable both xAPIC and x2APIC mode.
+ * - Hypervisor can support both xAVIC and x2AVIC in the same guest.
+ * - The mode can be switched at run-time.
+ */
+bool avic_hardware_setup(struct kvm_x86_ops *x86_ops)
+{
+	if (!npt_enabled)
+		return false;
+
+	if (boot_cpu_has(X86_FEATURE_AVIC)) {
+		avic_mode = AVIC_MODE_X1;
+		pr_info("AVIC enabled\n");
+	}
+
+	if (boot_cpu_has(X86_FEATURE_X2AVIC)) {
+		avic_mode = AVIC_MODE_X2;
+		pr_info("x2AVIC enabled\n");
+	}
+
+	if (avic_mode != AVIC_MODE_NONE)
+		amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
+
+	return !!avic_mode;
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index bd4c64b362d2..5ec770a1b4e8 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4806,13 +4806,9 @@ static __init int svm_hardware_setup(void)
 			nrips = false;
 	}
 
-	enable_apicv = avic = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC);
+	enable_apicv = avic = avic && avic_hardware_setup(&svm_x86_ops);
 
-	if (enable_apicv) {
-		pr_info("AVIC enabled\n");
-
-		amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
-	} else {
+	if (!enable_apicv) {
 		svm_x86_ops.vcpu_blocking = NULL;
 		svm_x86_ops.vcpu_unblocking = NULL;
 	}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index f77a7d2d39dd..c44326eeb3f2 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -571,6 +571,7 @@ extern struct kvm_x86_nested_ops svm_nested_ops;
 
 /* avic.c */
 
+bool avic_hardware_setup(struct kvm_x86_ops *ops);
 int avic_ga_log_notifier(u32 ga_tag);
 void avic_vm_destroy(struct kvm *kvm);
 int avic_vm_init(struct kvm *kvm);
-- 
2.25.1