It's now safe for the VMM to enable MTE in a guest, so expose the
capability to user space.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/arm.c      | 9 +++++++++
 arch/arm64/kvm/reset.c    | 4 ++++
 arch/arm64/kvm/sys_regs.c | 3 +++
 3 files changed, 16 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e720148232a0..28ce26a68f09 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c

@@ -93,6 +93,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
                r = 0;
                kvm->arch.return_nisv_io_abort_to_user = true;
                break;
+       case KVM_CAP_ARM_MTE:
+               if (!system_supports_mte() || kvm->created_vcpus)
+                       return -EINVAL;
+               r = 0;
+               kvm->arch.mte_enabled = true;
+               break;
        default:
                r = -EINVAL;
                break;

@@ -237,6 +243,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
                 */
                r = 1;
                break;
+       case KVM_CAP_ARM_MTE:
+               r = system_supports_mte();
+               break;
        case KVM_CAP_STEAL_TIME:
                r = kvm_arm_pvtime_supported();
                break;

diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index d37ebee085cf..9e6922b9503a 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c

@@ -244,6 +244,10 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
        switch (vcpu->arch.target) {
        default:
                if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
+                       if (vcpu->kvm->arch.mte_enabled) {
+                               ret = -EINVAL;
+                               goto out;
+                       }
                        pstate = VCPU_RESET_PSTATE_SVC;
                } else {
                        pstate = VCPU_RESET_PSTATE_EL1;

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 5c75b24eae21..f6f126eb6ac1 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c

@@ -1312,6 +1312,9 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
                                   const struct sys_reg_desc *rd)
 {
+       if (kvm_has_mte(vcpu->kvm))
+               return 0;
+
        return REG_HIDDEN;
 }

--

2.20.1

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