[RFC,v2,25/27] KVM: arm64: Disable MTE if tag storage is enabled

Commit Message

Alexandru Elisei Nov. 19, 2023, 4:57 p.m. UTC

KVM allows MTE enabled VMs to be created when the backing VMA does not have
MTE enabled.  Without changes to how KVM allocates memory for a VM, it is
impossible at the moment to discern when the corresponding tag storage
needs to be reserved.

For now, disable MTE in KVM if tag storage is enabled.

Signed-off-by: Alexandru Elisei <[e-mail]>
---
 arch/arm64/kvm/arm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e5f75f1f1085..5b33c532c62a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -29,6 +29,7 @@ 
 #include <linux/uaccess.h>
 #include <asm/ptrace.h>
 #include <asm/mman.h>
+#include <asm/mte_tag_storage.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
@@ -86,7 +87,8 @@  int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		break;
 	case KVM_CAP_ARM_MTE:
 		mutex_lock(&kvm->lock);
-		if (!system_supports_mte() || kvm->created_vcpus) {
+		if (!system_supports_mte() || tag_storage_enabled() ||
+		    kvm->created_vcpus) {
 			r = -EINVAL;
 		} else {
 			r = 0;
@@ -279,7 +281,7 @@  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = 1;
 		break;
 	case KVM_CAP_ARM_MTE:
-		r = system_supports_mte();
+		r = system_supports_mte() && !tag_storage_enabled();
 		break;
 	case KVM_CAP_STEAL_TIME:
 		r = kvm_arm_pvtime_supported();