[PATCH v3 21/62] iommu/amd: KVM: SVM: Use pi_desc_addr to derive ga_root_ptr

Sean Christopherson
2025-06-11T22:47:32Z

Use vcpu_data.pi_desc_addr instead of amd_iommu_pi_data.base to get the
GA root pointer. KVM is the only source of amd_iommu_pi_data.base, and
KVM's one and only path for writing amd_iommu_pi_data.base computes the
exact same value for vcpu_data.pi_desc_addr and amd_iommu_pi_data.base,
and fills amd_iommu_pi_data.base if and only if vcpu_data.pi_desc_addr is
valid, i.e. amd_iommu_pi_data.base is fully redundant.

Cc: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/avic.c | 7 +++++--
drivers/iommu/amd/iommu.c | 2 +-
include/linux/amd-iommu.h | 2 --
3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 3cf929ac117f..461300bc5608 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -893,8 +893,11 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,

enable_remapped_mode = false;

- /* Try to enable guest_mode in IRTE */
- pi.base = avic_get_backing_page_address(svm);
+ /*
+ * Try to enable guest_mode in IRTE. Note, the address
+ * of the vCPU's AVIC backing page is passed to the
+ * IOMMU via vcpu_info->pi_desc_addr.
+ */
pi.ga_tag = AVIC_GATAG(to_kvm_svm(kvm)->avic_vm_id,
svm->vcpu.vcpu_id);
pi.is_guest_mode = true;
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index f23635b062f0..512167f7aef4 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3888,7 +3888,7 @@ static int amd_ir_set_vcpu_affinity(struct irq_data *data, void *vcpu_info)
pi_data->ir_data = ir_data;

if (pi_data->is_guest_mode) {
- ir_data->ga_root_ptr = (pi_data->base >> 12);
+ ir_data->ga_root_ptr = (vcpu_pi_info->pi_desc_addr >> 12);
ir_data->ga_vector = vcpu_pi_info->vector;
ir_data->ga_tag = pi_data->ga_tag;
ret = amd_iommu_activate_guest_mode(ir_data);
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 1f9b13d803c5..deeefc92a5cf 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -19,8 +19,6 @@ struct amd_iommu;
*/
struct amd_iommu_pi_data {
u32 ga_tag;
- u64 base;
-
bool is_guest_mode;
struct vcpu_data *vcpu_data;
void *ir_data;
--
2.50.0.rc1.591.g9c95f17f64-goog