KVM: arm64: Track SVE state in the hypervisor vcpu structure

When dealing with a guest with SVE enabled, make sure the host SVE
state is pinned at EL2 S1, and that the hypervisor vCPU state is
correctly initialised (and then unpinned on teardown).

Co-authored-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20250416152648.2982950-2-qperret@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_host.h

@@ -971,20 +971,22 @@ struct kvm_vcpu_arch {
 #define vcpu_sve_zcr_elx(vcpu)						\
 	(unlikely(is_hyp_ctxt(vcpu)) ? ZCR_EL2 : ZCR_EL1)
 
-#define vcpu_sve_state_size(vcpu) ({					\
+#define sve_state_size_from_vl(sve_max_vl) ({				\
 	size_t __size_ret;						\
-	unsigned int __vcpu_vq;						\
+	unsigned int __vq;						\
 									\
-	if (WARN_ON(!sve_vl_valid((vcpu)->arch.sve_max_vl))) {		\
+	if (WARN_ON(!sve_vl_valid(sve_max_vl))) {			\
 		__size_ret = 0;						\
 	} else {							\
-		__vcpu_vq = vcpu_sve_max_vq(vcpu);			\
+		__vq = sve_vq_from_vl(sve_max_vl);			\
-		__size_ret = SVE_SIG_REGS_SIZE(__vcpu_vq);		\
+		__size_ret = SVE_SIG_REGS_SIZE(__vq);			\
 	}								\
 									\
 	__size_ret;							\
 })
 
+#define vcpu_sve_state_size(vcpu) sve_state_size_from_vl((vcpu)->arch.sve_max_vl)
+
 #define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \
 				 KVM_GUESTDBG_USE_SW_BP | \
 				 KVM_GUESTDBG_USE_HW | \

arch/arm64/kvm/hyp/nvhe/hyp-main.c

@@ -123,10 +123,6 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
 
 	hyp_vcpu->vcpu.arch.ctxt	= host_vcpu->arch.ctxt;
 
-	hyp_vcpu->vcpu.arch.sve_state	= kern_hyp_va(host_vcpu->arch.sve_state);
-	/* Limit guest vector length to the maximum supported by the host.  */
-	hyp_vcpu->vcpu.arch.sve_max_vl	= min(host_vcpu->arch.sve_max_vl, kvm_host_sve_max_vl);
-
 	hyp_vcpu->vcpu.arch.mdcr_el2	= host_vcpu->arch.mdcr_el2;
 	hyp_vcpu->vcpu.arch.hcr_el2 &= ~(HCR_TWI | HCR_TWE);
 	hyp_vcpu->vcpu.arch.hcr_el2 |= READ_ONCE(host_vcpu->arch.hcr_el2) &

arch/arm64/kvm/hyp/nvhe/pkvm.c

@@ -372,6 +372,18 @@ static void unpin_host_vcpu(struct kvm_vcpu *host_vcpu)
 		hyp_unpin_shared_mem(host_vcpu, host_vcpu + 1);
 }
 
+static void unpin_host_sve_state(struct pkvm_hyp_vcpu *hyp_vcpu)
+{
+	void *sve_state;
+
+	if (!vcpu_has_feature(&hyp_vcpu->vcpu, KVM_ARM_VCPU_SVE))
+		return;
+
+	sve_state = kern_hyp_va(hyp_vcpu->vcpu.arch.sve_state);
+	hyp_unpin_shared_mem(sve_state,
+			     sve_state + vcpu_sve_state_size(&hyp_vcpu->vcpu));
+}
+
 static void unpin_host_vcpus(struct pkvm_hyp_vcpu *hyp_vcpus[],
 			     unsigned int nr_vcpus)
 {
@@ -384,6 +396,7 @@ static void unpin_host_vcpus(struct pkvm_hyp_vcpu *hyp_vcpus[],
 			continue;
 
 		unpin_host_vcpu(hyp_vcpu->host_vcpu);
+		unpin_host_sve_state(hyp_vcpu);
 	}
 }
 
@@ -398,12 +411,40 @@ static void init_pkvm_hyp_vm(struct kvm *host_kvm, struct pkvm_hyp_vm *hyp_vm,
 	pkvm_init_features_from_host(hyp_vm, host_kvm);
 }
 
-static void pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
+static int pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
 {
 	struct kvm_vcpu *vcpu = &hyp_vcpu->vcpu;
+	unsigned int sve_max_vl;
+	size_t sve_state_size;
+	void *sve_state;
+	int ret = 0;
 
-	if (!vcpu_has_feature(vcpu, KVM_ARM_VCPU_SVE))
+	if (!vcpu_has_feature(vcpu, KVM_ARM_VCPU_SVE)) {
 		vcpu_clear_flag(vcpu, VCPU_SVE_FINALIZED);
+		return 0;
+	}
+
+	/* Limit guest vector length to the maximum supported by the host. */
+	sve_max_vl = min(READ_ONCE(host_vcpu->arch.sve_max_vl), kvm_host_sve_max_vl);
+	sve_state_size = sve_state_size_from_vl(sve_max_vl);
+	sve_state = kern_hyp_va(READ_ONCE(host_vcpu->arch.sve_state));
+
+	if (!sve_state || !sve_state_size) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	ret = hyp_pin_shared_mem(sve_state, sve_state + sve_state_size);
+	if (ret)
+		goto err;
+
+	vcpu->arch.sve_state = sve_state;
+	vcpu->arch.sve_max_vl = sve_max_vl;
+
+	return 0;
+err:
+	clear_bit(KVM_ARM_VCPU_SVE, vcpu->kvm->arch.vcpu_features);
+	return ret;
 }
 
 static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
@@ -432,7 +473,7 @@ static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
 	if (ret)
 		goto done;
 
-	pkvm_vcpu_init_sve(hyp_vcpu, host_vcpu);
+	ret = pkvm_vcpu_init_sve(hyp_vcpu, host_vcpu);
 done:
 	if (ret)
 		unpin_host_vcpu(host_vcpu);