[PATCH 3/6] svm: Add support for APIC_ACCESS_PAGE_PRIVATE_MEMSLOT setup/destroy

[Suthikulpanit, Suravee]

Activate/deactivate AVIC requires setting/unsetting the memory region used
for 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.suthikulpa...@amd.com>
---
 arch/x86/kvm/svm.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 4cf93a729ad8..f41f34f70dde 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1666,7 +1666,7 @@ 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;
@@ -1675,10 +1675,14 @@ static int avic_init_access_page(struct kvm_vcpu *vcpu)
        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;
 
@@ -1688,6 +1692,26 @@ 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;
@@ -1695,7 +1719,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
        int id = vcpu->vcpu_id;
        struct vcpu_svm *svm = to_svm(vcpu);
 
-       ret = avic_init_access_page(vcpu);
+       ret = avic_setup_access_page(vcpu, true);
        if (ret)
                return ret;
 
-- 
2.17.1