Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
From:   Alexandru Elisei <alexandru.elisei@arm.com>
To:     catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev,
        maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com,
        yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org,
        mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org,
        rppt@kernel.org, hughd@google.com
Cc:     pcc@google.com, steven.price@arm.com, anshuman.khandual@arm.com,
        vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com,
        kcc@google.com, hyesoo.yu@samsung.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org,
        linux-trace-kernel@vger.kernel.org
Subject: [PATCH RFC v2 25/27] KVM: arm64: Disable MTE if tag storage is enabled
Date:   Sun, 19 Nov 2023 16:57:19 +0000
Message-Id: <20231119165721.9849-26-alexandru.elisei@arm.com>
In-Reply-To: <20231119165721.9849-1-alexandru.elisei@arm.com>
References: <20231119165721.9849-1-alexandru.elisei@arm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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