linux-kernel - [PATCH RFC 36/37] KVM: arm64: Disable MTE is tag storage is enabled

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Message-Id: <20230823131350.114942-37-alexandru.elisei@arm.com>
Date:   Wed, 23 Aug 2023 14:13:49 +0100
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 36/37] KVM: arm64: Disable MTE is tag storage is enabled

KVM allows MTE enabled VMs to be created when the backing memory is does
not have MTE enabled.  Without changes to how KVM allocates memory for a
VM, it is impossible 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 72dc53a75d1c..1f39c2d5223d 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -38,6 +38,7 @@
 #include <asm/kvm_mmu.h>
 #include <asm/kvm_pkvm.h>
 #include <asm/kvm_emulate.h>
+#include <asm/memory_metadata.h>
 #include <asm/sections.h>
 
 #include <kvm/arm_hypercalls.h>
@@ -85,7 +86,8 @@ 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() || metadata_storage_enabled() ||
+		    kvm->created_vcpus) {
 			r = -EINVAL;
 		} else {
 			r = 0;
@@ -277,7 +279,7 @@ 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() && !metadata_storage_enabled();
 		break;
 	case KVM_CAP_STEAL_TIME:
 		r = kvm_arm_pvtime_supported();
-- 
2.41.0