linux-kernel - [PATCH v3 21/62] iommu/amd: KVM: SVM: Use pi_desc_addr to derive ga_root

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Message-ID: <20250611224604.313496-23-seanjc@google.com>
Date: Wed, 11 Jun 2025 15:45:24 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, 
	David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Sairaj Kodilkar <sarunkod@....com>, Vasant Hegde <vasant.hegde@....com>, 
	Maxim Levitsky <mlevitsk@...hat.com>, Joao Martins <joao.m.martins@...cle.com>, 
	Francesco Lavra <francescolavra.fl@...il.com>, David Matlack <dmatlack@...gle.com>
Subject: [PATCH v3 21/62] iommu/amd: KVM: SVM: Use pi_desc_addr to derive ga_root_ptr

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@...hat.com>
Reviewed-by: Joao Martins <joao.m.martins@...cle.com>
Reviewed-by: Vasant Hegde <vasant.hegde@....com>
Tested-by: Sairaj Kodilkar <sarunkod@....com>
Signed-off-by: Sean Christopherson <seanjc@...gle.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