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

Alexandru Elisei
2023-11-19T17:00:32Z

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 <alexandru.elisei@arm.com>
---
arch/arm64/kvm/arm.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

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();
--
2.42.1