The kernel allows heterogeneous systems where FEAT_SPE is not present on
all CPUs. This presents a challenge for KVM, as it will have to touch the
SPE registers when emulating SPE for a guest, and those accesses will cause
an undefined exception if SPE is not present on the CPU.
Avoid this situation by keeping a cpumask of CPUs that the VCPU is
allowed run on, which for SPE is the reunion of all CPUs that support
SPE, and refuse to run the VCPU on a CPU which is not part of the
cpumask.
Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
---
arch/arm64/include/asm/kvm_host.h | 3 +++
arch/arm64/kvm/arm.c | 15 +++++++++++++++
arch/arm64/kvm/spe.c | 2 ++
3 files changed, 20 insertions(+)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8b3faed48914..96ce98f6135d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -405,6 +405,9 @@ struct kvm_vcpu_arch {
u64 last_steal;
gpa_t base;
} steal;
+
+ cpumask_var_t supported_cpus;
+ bool cpu_not_supported;
};
/* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index b2997b919be2..8a7c01d1df58 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -351,6 +351,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
+ if (!zalloc_cpumask_var(&vcpu->arch.supported_cpus, GFP_KERNEL))
+ return -ENOMEM;
+
/* Set up the timer */
kvm_timer_vcpu_init(vcpu);
@@ -378,6 +381,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm)))
static_branch_dec(&userspace_irqchip_in_use);
+ free_cpumask_var(vcpu->arch.supported_cpus);
kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
kvm_timer_vcpu_terminate(vcpu);
kvm_pmu_vcpu_destroy(vcpu);
@@ -456,6 +460,10 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
if (vcpu_has_ptrauth(vcpu))
vcpu_ptrauth_disable(vcpu);
kvm_arch_vcpu_load_debug_state_flags(vcpu);
+
+ if (!cpumask_empty(vcpu->arch.supported_cpus) &&
+ !cpumask_test_cpu(smp_processor_id(), vcpu->arch.supported_cpus))
+ vcpu->arch.cpu_not_supported = true;
}
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -893,6 +901,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
*/
preempt_disable();
+ if (unlikely(vcpu->arch.cpu_not_supported)) {
+ vcpu->arch.cpu_not_supported = false;
+ ret = -ENOEXEC;
+ preempt_enable();
+ continue;
+ }
+
kvm_pmu_flush_hwstate(vcpu);
local_irq_disable();
diff --git a/arch/arm64/kvm/spe.c b/arch/arm64/kvm/spe.c
index 7c6f94358cc1..f3863728bab6 100644
--- a/arch/arm64/kvm/spe.c
+++ b/arch/arm64/kvm/spe.c
@@ -40,5 +40,7 @@ int kvm_spe_vcpu_enable_spe(struct kvm_vcpu *vcpu)
if (vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT))
return -EINVAL;
+ cpumask_copy(vcpu->arch.supported_cpus, &supported_cpus);
+
return 0;
}
--
2.33.1
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