[RFC PATCH v3 11/27] KVM: SVM: Disable IPIv for Secure AVIC

["Naveen N Rao (AMD)" <naveen@kernel.org>]

Secure AVIC does not have IPI virtualization (except for Self-IPIs which
is not relevant for KVM), i.e., guest ICR writes are not accelerated by
the hardware but results in a #VC that the guest is expected to handle
with the help of the hypervisor. This also means there are no AVIC
Physical/Logical ID tables to be setup.

Add a helper avic_ipiv_is_supported() to query support for IPIv and use
the same to short-circuit various AVIC flows related to AVIC data
structures such as the Physical and Logical ID tables for Secure AVIC.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
---
 arch/x86/kvm/svm/svm.h  |  1 +
 arch/x86/kvm/svm/avic.c | 23 ++++++++++++++++++++++-
 arch/x86/kvm/svm/sev.c  |  4 +++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 1157d022bac1..e48744f6d756 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -131,6 +131,7 @@ struct kvm_svm {
 	u32 *avic_logical_id_table;
 	u64 *avic_physical_id_table;
 	struct hlist_node hnode;
+	bool avic_ipiv_is_not_supported;
 
 #ifdef CONFIG_KVM_AMD_SEV
 	struct kvm_sev_info sev_info;
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index c9e375c5a9c1..0a4e91e15e74 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -76,6 +76,12 @@ static bool avic_ipiv_is_soft_disabled(void)
 	return !enable_ipiv;
 }
 
+/* IPIv is not supported in Secure AVIC mode, no AVIC tables necessary */
+static bool avic_ipiv_is_supported(struct kvm *kvm)
+{
+	return !to_kvm_svm(kvm)->avic_ipiv_is_not_supported;
+}
+
 static int avic_param_set(const char *val, const struct kernel_param *kp)
 {
 	if (val && sysfs_streq(val, "auto")) {
@@ -364,7 +370,7 @@ int avic_vcpu_precreate(struct kvm *kvm)
 {
 	int r;
 
-	if (!irqchip_in_kernel(kvm) || WARN_ON_ONCE(!enable_apicv))
+	if (!irqchip_in_kernel(kvm) || WARN_ON_ONCE(!enable_apicv) || !avic_ipiv_is_supported(kvm))
 		return 0;
 
 	/*
@@ -435,6 +441,9 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
 	u32 id = vcpu->vcpu_id;
 	u64 new_entry;
 
+	if (!avic_ipiv_is_supported(vcpu->kvm))
+		return 0;
+
 	/*
 	 * Inhibit AVIC if the vCPU ID is bigger than what is supported by AVIC
 	 * hardware.  Immediately clear apicv_active, i.e. don't wait until the
@@ -1069,6 +1078,9 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu,
 
 	lockdep_assert_preemption_disabled();
 
+	if (!avic_ipiv_is_supported(vcpu->kvm))
+		return;
+
 	if (WARN_ON(h_physical_id & ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK))
 		return;
 
@@ -1113,6 +1125,9 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu,
 
 void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+	if (!avic_ipiv_is_supported(vcpu->kvm))
+		return;
+
 	/*
 	 * No need to update anything if the vCPU is blocking, i.e. if the vCPU
 	 * is being scheduled in after being preempted.  The CPU entries in the
@@ -1135,6 +1150,9 @@ static void __avic_vcpu_put(struct kvm_vcpu *vcpu, enum avic_vcpu_action action)
 
 	lockdep_assert_preemption_disabled();
 
+	if (!avic_ipiv_is_supported(vcpu->kvm))
+		return;
+
 	if (WARN_ON_ONCE(vcpu->vcpu_id * sizeof(entry) >=
 			 PAGE_SIZE << avic_get_physical_id_table_order(vcpu->kvm)))
 		return;
@@ -1185,6 +1203,9 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
 	 */
 	u64 entry = to_svm(vcpu)->avic_physical_id_entry;
 
+	if (!avic_ipiv_is_supported(vcpu->kvm))
+		return;
+
 	/*
 	 * Nothing to do if IsRunning == '0' due to vCPU blocking, i.e. if the
 	 * vCPU is preempted while its in the process of blocking.  WARN if the
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a47bb417bd98..a12e7e9f9fa1 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -566,8 +566,10 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
 	INIT_LIST_HEAD(&sev->mirror_vms);
 	sev->need_init = false;
 
-	if (snp_is_secure_avic_enabled(kvm))
+	if (snp_is_secure_avic_enabled(kvm)) {
 		kvm->arch.apicv_has_irq_bypass = false;
+		to_kvm_svm(kvm)->avic_ipiv_is_not_supported = true;
+	}
 
 	kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_SEV);
 
-- 
2.54.0