[PATCH v2 08/15] svm: Add support for setup/destroy virutal APIC backing page for AVIC

["Suthikulpanit, Suravee" <Suravee.Suthikulpanit@xxxxxxx>]

Activate/deactivate AVIC requires setting/unsetting the memory region used
for virtual APIC backing page (APIC_ACCESS_PAGE_PRIVATE_MEMSLOT).
So, re-factor avic_init_access_page() to avic_setup_access_page()
and add srcu_read_lock/unlock, which are needed to allow this function
to be called during run-time.

Also, introduce avic_destroy_access_page() to unset the page when
deactivate AVIC.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 arch/x86/kvm/svm.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 43 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index b674cd0..47f2439 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1468,7 +1468,9 @@ static u64 svm_write_l1_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 static void avic_init_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb *vmcb = svm->vmcb;
-	struct kvm_svm *kvm_svm = to_kvm_svm(svm->vcpu.kvm);
+	struct kvm *kvm = svm->vcpu.kvm;
+	struct kvm_svm *kvm_svm = to_kvm_svm(kvm);
+
 	phys_addr_t bpa = __sme_set(page_to_phys(svm->avic_backing_page));
 	phys_addr_t lpa = __sme_set(page_to_phys(kvm_svm->avic_logical_id_table_page));
 	phys_addr_t ppa = __sme_set(page_to_phys(kvm_svm->avic_physical_id_table_page));
@@ -1477,7 +1479,13 @@ static void avic_init_vmcb(struct vcpu_svm *svm)
 	vmcb->control.avic_logical_id = lpa & AVIC_HPA_MASK;
 	vmcb->control.avic_physical_id = ppa & AVIC_HPA_MASK;
 	vmcb->control.avic_physical_id |= AVIC_MAX_PHYSICAL_ID_COUNT;
-	vmcb->control.int_ctl |= AVIC_ENABLE_MASK;
+
+	mutex_lock(&kvm->arch.apicv_lock);
+	if (kvm->arch.apicv_state == APICV_ACTIVATED)
+		vmcb->control.int_ctl |= AVIC_ENABLE_MASK;
+	else
+		vmcb->control.int_ctl &= ~AVIC_ENABLE_MASK;
+	mutex_unlock(&kvm->arch.apicv_lock);
 }
 
 static void init_vmcb(struct vcpu_svm *svm)
@@ -1660,19 +1668,24 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
  * field of the VMCB. Therefore, we set up the
  * APIC_ACCESS_PAGE_PRIVATE_MEMSLOT (4KB) here.
  */
-static int avic_init_access_page(struct kvm_vcpu *vcpu)
+static int avic_setup_access_page(struct kvm_vcpu *vcpu, bool init)
 {
 	struct kvm *kvm = vcpu->kvm;
 	int ret = 0;
 
 	mutex_lock(&kvm->slots_lock);
+
 	if (kvm->arch.apic_access_page_done)
 		goto out;
 
+	if (!init)
+		srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
 	ret = __x86_set_memory_region(kvm,
 				      APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
 				      APIC_DEFAULT_PHYS_BASE,
 				      PAGE_SIZE);
+	if (!init)
+		vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
 	if (ret)
 		goto out;
 
@@ -1682,14 +1695,39 @@ static int avic_init_access_page(struct kvm_vcpu *vcpu)
 	return ret;
 }
 
+static void avic_destroy_access_page(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+
+	mutex_lock(&kvm->slots_lock);
+
+	if (!kvm->arch.apic_access_page_done)
+		goto out;
+
+	srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
+	__x86_set_memory_region(kvm,
+				APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
+				APIC_DEFAULT_PHYS_BASE,
+				0);
+	vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
+	kvm->arch.apic_access_page_done = false;
+out:
+	mutex_unlock(&kvm->slots_lock);
+}
+
 static int avic_init_backing_page(struct kvm_vcpu *vcpu)
 {
-	int ret;
+	int ret = 0;
 	u64 *entry, new_entry;
 	int id = vcpu->vcpu_id;
+	struct kvm *kvm = vcpu->kvm;
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	ret = avic_init_access_page(vcpu);
+	mutex_lock(&kvm->arch.apicv_lock);
+	if (kvm->arch.apicv_state == APICV_ACTIVATED)
+		ret = avic_setup_access_page(vcpu, true);
+	mutex_unlock(&kvm->arch.apicv_lock);
+
 	if (ret)
 		return ret;
 
-- 
1.8.3.1