[PATCH v13 42/48] arm64: RMI: Propagate max SVE vector length from RMM

Steven Price
2026-03-18T15:56:58Z

From: Jean-Philippe Brucker <jean-philippe@linaro.org>

RMM provides the maximum vector length it supports for a guest in its
feature register. Make it visible to the rest of KVM and to userspace
via KVM_REG_ARM64_SVE_VLS.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
arch/arm64/include/asm/kvm_host.h | 2 +-
arch/arm64/include/asm/kvm_rmi.h | 1 +
arch/arm64/kvm/guest.c | 2 +-
arch/arm64/kvm/reset.c | 12 ++++++++++--
arch/arm64/kvm/rmi.c | 6 ++++++
5 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1efea996f474..1d5fb001408c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -78,9 +78,9 @@ enum kvm_mode kvm_get_mode(void);
static inline enum kvm_mode kvm_get_mode(void) { return KVM_MODE_NONE; };
#endif

-extern unsigned int __ro_after_init kvm_sve_max_vl;
extern unsigned int __ro_after_init kvm_host_sve_max_vl;
int __init kvm_arm_init_sve(void);
+unsigned int kvm_sve_get_max_vl(struct kvm *kvm);

u32 __attribute_const__ kvm_target_cpu(void);
void kvm_reset_vcpu(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
index 8f871daf6540..b914b9a84bd8 100644
--- a/arch/arm64/include/asm/kvm_rmi.h
+++ b/arch/arm64/include/asm/kvm_rmi.h
@@ -87,6 +87,7 @@ struct realm_rec {
void kvm_init_rmi(void);
u32 kvm_realm_ipa_limit(void);
u8 kvm_realm_max_pmu_counters(void);
+unsigned int kvm_realm_sve_max_vl(void);

u64 kvm_realm_reset_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val);

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 7cf919db1adc..705c2ccc335d 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -375,7 +375,7 @@ static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
if (vq_present(vqs, vq))
max_vq = vq;

- if (max_vq > sve_vq_from_vl(kvm_sve_max_vl))
+ if (max_vq > sve_vq_from_vl(kvm_sve_get_max_vl(vcpu->kvm)))
return -EINVAL;

/*
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 4bbf58892928..08883c9e848f 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -46,7 +46,7 @@ unsigned int __ro_after_init kvm_host_sve_max_vl;
#define VCPU_RESET_PSTATE_SVC (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT | \
PSR_AA32_I_BIT | PSR_AA32_F_BIT)

-unsigned int __ro_after_init kvm_sve_max_vl;
+static unsigned int __ro_after_init kvm_sve_max_vl;

int __init kvm_arm_init_sve(void)
{
@@ -76,9 +76,17 @@ int __init kvm_arm_init_sve(void)
return 0;
}

+unsigned int kvm_sve_get_max_vl(struct kvm *kvm)
+{
+ if (kvm_is_realm(kvm))
+ return kvm_realm_sve_max_vl();
+ else
+ return kvm_sve_max_vl;
+}
+
static void kvm_vcpu_enable_sve(struct kvm_vcpu *vcpu)
{
- vcpu->arch.sve_max_vl = kvm_sve_max_vl;
+ vcpu->arch.sve_max_vl = kvm_sve_get_max_vl(vcpu->kvm);

/*
* Userspace can still customize the vector lengths by writing
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index f29c04d2318a..f2aeda7f5e6e 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -217,6 +217,12 @@ u8 kvm_realm_max_pmu_counters(void)
return u64_get_bits(rmm_feat_reg0, RMI_FEATURE_REGISTER_0_PMU_NUM_CTRS);
}

+unsigned int kvm_realm_sve_max_vl(void)
+{
+ return sve_vl_from_vq(u64_get_bits(rmm_feat_reg0,
+ RMI_FEATURE_REGISTER_0_SVE_VL) + 1);
+}
+
u64 kvm_realm_reset_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
{
u32 bps = u64_get_bits(rmm_feat_reg0, RMI_FEATURE_REGISTER_0_NUM_BPS);
--
2.43.0