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

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Message-Id: <20231119165721.9849-26-alexandru.elisei@arm.com>
Date:   Sun, 19 Nov 2023 16:57:19 +0000
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     catalin.marinas@....com, will@...nel.org, oliver.upton@...ux.dev,
        maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        yuzenghui@...wei.com, arnd@...db.de, akpm@...ux-foundation.org,
        mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, mhiramat@...nel.org,
        rppt@...nel.org, hughd@...gle.com
Cc:     pcc@...gle.com, steven.price@....com, anshuman.khandual@....com,
        vincenzo.frascino@....com, david@...hat.com, eugenis@...gle.com,
        kcc@...gle.com, hyesoo.yu@...sung.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-trace-kernel@...r.kernel.org
Subject: [PATCH RFC v2 25/27] KVM: arm64: Disable MTE if tag storage is enabled

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@....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