[PATCH RFC 6/7] ARM64: KVM: Support heterogeneous system

[Shannon Zhao <zhaoshenglong@xxxxxxxxxx>]

From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>

When initializing KVM, check whether physical hardware is a
heterogeneous system through the MIDR values. If so, force userspace to
set the KVM_ARM_VCPU_CROSS feature bit. Otherwise, it should fail to
initialize VCPUs.

Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
---
 arch/arm/kvm/arm.c       | 26 ++++++++++++++++++++++++++
 include/uapi/linux/kvm.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index bdceb19..21ec070 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -46,6 +46,7 @@
 #include <asm/kvm_coproc.h>
 #include <asm/kvm_psci.h>
 #include <asm/sections.h>
+#include <asm/cputype.h>
 
 #ifdef REQUIRES_VIRT
 __asm__(".arch_extension	virt");
@@ -65,6 +66,7 @@ static unsigned int kvm_vmid_bits __read_mostly;
 static DEFINE_SPINLOCK(kvm_vmid_lock);
 
 static bool vgic_present;
+static bool heterogeneous_system;
 
 static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
 
@@ -210,6 +212,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_ARM_CROSS_VCPU:
 		r = 1;
 		break;
+	case KVM_CAP_ARM_HETEROGENEOUS:
+		r = heterogeneous_system;
+		break;
 	case KVM_CAP_COALESCED_MMIO:
 		r = KVM_COALESCED_MMIO_PAGE_OFFSET;
 		break;
@@ -812,6 +817,12 @@ static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
 	int phys_target = kvm_target_cpu();
 	bool cross_vcpu = kvm_vcpu_has_feature_cross_cpu(init);
 
+	if (heterogeneous_system && !cross_vcpu) {
+		kvm_err("%s:Host is a heterogeneous system, set KVM_ARM_VCPU_CROSS bit\n",
+			__func__);
+		return -EINVAL;
+	}
+
 	if (!cross_vcpu && init->target != phys_target)
 		return -EINVAL;
 
@@ -1397,6 +1408,11 @@ static void check_kvm_target_cpu(void *ret)
 	*(int *)ret = kvm_target_cpu();
 }
 
+static void get_physical_cpu_midr(void *midr)
+{
+	*(u32 *)midr = read_cpuid_id();
+}
+
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr)
 {
 	struct kvm_vcpu *vcpu;
@@ -1417,6 +1433,7 @@ int kvm_arch_init(void *opaque)
 {
 	int err;
 	int ret, cpu;
+	u32 current_midr, midr;
 
 	if (!is_hyp_mode_available()) {
 		kvm_err("HYP mode not available\n");
@@ -1431,6 +1448,15 @@ int kvm_arch_init(void *opaque)
 		}
 	}
 
+	current_midr = read_cpuid_id();
+	for_each_online_cpu(cpu) {
+		smp_call_function_single(cpu, get_physical_cpu_midr, &midr, 1);
+		if (current_midr != midr) {
+			heterogeneous_system = true;
+			break;
+		}
+	}
+
 	err = init_common_resources();
 	if (err)
 		return err;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 46115a2..cc2b63d 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -872,6 +872,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_MSI_DEVID 131
 #define KVM_CAP_PPC_HTM 132
 #define KVM_CAP_ARM_CROSS_VCPU 133
+#define KVM_CAP_ARM_HETEROGENEOUS 134
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.0.4


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