diff mbox series

[v3,2/2] arm64: kvm: Introduce MTE VCPU feature

Message ID 20200925093607.3051-3-steven.price@arm.com
State New
Headers show
Series MTE support for KVM guest | expand

Commit Message

Steven Price Sept. 25, 2020, 9:36 a.m. UTC
Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
for a VM. This exposes the feature to the guest and automatically tags
memory pages touched by the VM as PG_mte_tagged (and clears the tags
storage) to ensure that the guest cannot see stale tags, and so that the
tags are correctly saved/restored across swap.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_emulate.h |  3 +++
 arch/arm64/include/asm/kvm_host.h    |  3 +++
 arch/arm64/kvm/arm.c                 |  9 +++++++++
 arch/arm64/kvm/mmu.c                 | 15 +++++++++++++++
 arch/arm64/kvm/sys_regs.c            |  6 +++++-
 include/uapi/linux/kvm.h             |  1 +
 6 files changed, 36 insertions(+), 1 deletion(-)

Comments

Andrew Jones Oct. 2, 2020, 2:30 p.m. UTC | #1
On Fri, Sep 25, 2020 at 10:36:07AM +0100, Steven Price wrote:
> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
> for a VM. This exposes the feature to the guest and automatically tags
> memory pages touched by the VM as PG_mte_tagged (and clears the tags
> storage) to ensure that the guest cannot see stale tags, and so that the
> tags are correctly saved/restored across swap.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_emulate.h |  3 +++
>  arch/arm64/include/asm/kvm_host.h    |  3 +++
>  arch/arm64/kvm/arm.c                 |  9 +++++++++
>  arch/arm64/kvm/mmu.c                 | 15 +++++++++++++++
>  arch/arm64/kvm/sys_regs.c            |  6 +++++-
>  include/uapi/linux/kvm.h             |  1 +
>  6 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 49a55be2b9a2..4923a566ae6e 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -79,6 +79,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>  	    vcpu_el1_is_32bit(vcpu))
>  		vcpu->arch.hcr_el2 |= HCR_TID2;
> +
> +	if (vcpu->kvm->arch.mte_enabled)
> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>  }
>  
>  static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 4f4360dd149e..1379300c1487 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -110,6 +110,9 @@ struct kvm_arch {
>  	 * supported.
>  	 */
>  	bool return_nisv_io_abort_to_user;
> +
> +	/* Memory Tagging Extension enabled for the guest */
> +	bool mte_enabled;
>  };
>  
>  struct kvm_vcpu_fault_info {
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 46dc3d75cf13..624edca0a1fa 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -87,6 +87,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>  		r = 0;
>  		kvm->arch.return_nisv_io_abort_to_user = true;
>  		break;
> +	case KVM_CAP_ARM_MTE:
> +		if (!system_supports_mte() || kvm->created_vcpus)
> +			return -EINVAL;
> +		r = 0;
> +		kvm->arch.mte_enabled = true;
> +		break;
>  	default:
>  		r = -EINVAL;
>  		break;
> @@ -206,6 +212,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  		 */
>  		r = 1;
>  		break;
> +	case KVM_CAP_ARM_MTE:
> +		r = system_supports_mte();
> +		break;
>  	default:
>  		r = kvm_arch_vm_ioctl_check_extension(kvm, ext);
>  		break;
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index ba00bcc0c884..befb9e1f0aa6 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1949,6 +1949,21 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (vma_pagesize == PAGE_SIZE && !force_pte)
>  		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>  							   &pfn, &fault_ipa);
> +	if (system_supports_mte() && kvm->arch.mte_enabled && pfn_valid(pfn)) {

'system_supports_mte() && kvm->arch.mte_enabled' is redundant, but I
assume system_supports_mte() is there to improve the efficiency of the
branch, as it's using cpus_have_const_cap(). Maybe a helper like

 static inline bool kvm_arm_mte_enabled(struct kvm *kvm)
 {
   return system_supports_mte() && kvm->arch.mte_enabled;
 }

would allow both the more efficient branch and look less confusing
where it gets used.

> +		/*
> +		 * VM will be able to see the page's tags, so we must ensure
> +		 * they have been initialised.
> +		 */
> +		struct page *page = pfn_to_page(pfn);
> +		long i, nr_pages = compound_nr(page);
> +
> +		/* if PG_mte_tagged is set, tags have already been initialised */
> +		for (i = 0; i < nr_pages; i++, page++) {
> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> +				mte_clear_page_tags(page_address(page));
> +		}
> +	}
> +
>  	if (writable)
>  		kvm_set_pfn_dirty(pfn);
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index a655f172b5ad..5010a47152b4 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1132,7 +1132,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>  			val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
>  		val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT);
>  	} else if (id == SYS_ID_AA64PFR1_EL1) {
> -		val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
> +		if (!vcpu->kvm->arch.mte_enabled)
> +			val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
>  	} else if (id == SYS_ID_AA64ISAR1_EL1 && !vcpu_has_ptrauth(vcpu)) {
>  		val &= ~((0xfUL << ID_AA64ISAR1_APA_SHIFT) |
>  			 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
> @@ -1394,6 +1395,9 @@ static bool access_mte_regs(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
>  				   const struct sys_reg_desc *rd)
>  {
> +	if (vcpu->kvm->arch.mte_enabled)
> +		return 0;
> +
>  	return REG_HIDDEN_USER | REG_HIDDEN_GUEST;
>  }
>  
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index f6d86033c4fa..87678ed82ab4 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1035,6 +1035,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_LAST_CPU 184
>  #define KVM_CAP_SMALLER_MAXPHYADDR 185
>  #define KVM_CAP_S390_DIAG318 186
> +#define KVM_CAP_ARM_MTE 188
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> -- 
> 2.20.1
> 
>

Besides the helper suggestion nit

Reviewed-by: Andrew Jones <drjones@redhat.com>
Steven Price Oct. 2, 2020, 3:30 p.m. UTC | #2
On 02/10/2020 15:30, Andrew Jones wrote:
> On Fri, Sep 25, 2020 at 10:36:07AM +0100, Steven Price wrote:
>> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
>> for a VM. This exposes the feature to the guest and automatically tags
>> memory pages touched by the VM as PG_mte_tagged (and clears the tags
>> storage) to ensure that the guest cannot see stale tags, and so that the
>> tags are correctly saved/restored across swap.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h |  3 +++
>>   arch/arm64/include/asm/kvm_host.h    |  3 +++
>>   arch/arm64/kvm/arm.c                 |  9 +++++++++
>>   arch/arm64/kvm/mmu.c                 | 15 +++++++++++++++
>>   arch/arm64/kvm/sys_regs.c            |  6 +++++-
>>   include/uapi/linux/kvm.h             |  1 +
>>   6 files changed, 36 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 49a55be2b9a2..4923a566ae6e 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -79,6 +79,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>>   	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>>   	    vcpu_el1_is_32bit(vcpu))
>>   		vcpu->arch.hcr_el2 |= HCR_TID2;
>> +
>> +	if (vcpu->kvm->arch.mte_enabled)
>> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>>   }
>>   
>>   static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 4f4360dd149e..1379300c1487 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -110,6 +110,9 @@ struct kvm_arch {
>>   	 * supported.
>>   	 */
>>   	bool return_nisv_io_abort_to_user;
>> +
>> +	/* Memory Tagging Extension enabled for the guest */
>> +	bool mte_enabled;
>>   };
>>   
>>   struct kvm_vcpu_fault_info {
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 46dc3d75cf13..624edca0a1fa 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -87,6 +87,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>>   		r = 0;
>>   		kvm->arch.return_nisv_io_abort_to_user = true;
>>   		break;
>> +	case KVM_CAP_ARM_MTE:
>> +		if (!system_supports_mte() || kvm->created_vcpus)
>> +			return -EINVAL;
>> +		r = 0;
>> +		kvm->arch.mte_enabled = true;
>> +		break;
>>   	default:
>>   		r = -EINVAL;
>>   		break;
>> @@ -206,6 +212,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>>   		 */
>>   		r = 1;
>>   		break;
>> +	case KVM_CAP_ARM_MTE:
>> +		r = system_supports_mte();
>> +		break;
>>   	default:
>>   		r = kvm_arch_vm_ioctl_check_extension(kvm, ext);
>>   		break;
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index ba00bcc0c884..befb9e1f0aa6 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -1949,6 +1949,21 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	if (vma_pagesize == PAGE_SIZE && !force_pte)
>>   		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>>   							   &pfn, &fault_ipa);
>> +	if (system_supports_mte() && kvm->arch.mte_enabled && pfn_valid(pfn)) {
> 
> 'system_supports_mte() && kvm->arch.mte_enabled' is redundant, but I
> assume system_supports_mte() is there to improve the efficiency of the
> branch, as it's using cpus_have_const_cap().

system_supports_mte() compiles to 0 when MTE support isn't built in, so 
this code can be removed by the compiler, whereas with 
kvm->arch.mte_enabled I doubt the compiler can deduce that it is never set.

> Maybe a helper like
> 
>   static inline bool kvm_arm_mte_enabled(struct kvm *kvm)
>   {
>     return system_supports_mte() && kvm->arch.mte_enabled;
>   }
> 
> would allow both the more efficient branch and look less confusing
> where it gets used.

I wasn't sure it was worth having a helper since this was the only place 
checking this condition. It's also a bit tricky putting this in a 
logical header file, kvm_host.h doesn't work because struct kvm hasn't 
been defined by then.

Steve

>> +		/*
>> +		 * VM will be able to see the page's tags, so we must ensure
>> +		 * they have been initialised.
>> +		 */
>> +		struct page *page = pfn_to_page(pfn);
>> +		long i, nr_pages = compound_nr(page);
>> +
>> +		/* if PG_mte_tagged is set, tags have already been initialised */
>> +		for (i = 0; i < nr_pages; i++, page++) {
>> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
>> +				mte_clear_page_tags(page_address(page));
>> +		}
>> +	}
>> +
>>   	if (writable)
>>   		kvm_set_pfn_dirty(pfn);
>>   
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index a655f172b5ad..5010a47152b4 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1132,7 +1132,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>>   			val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
>>   		val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT);
>>   	} else if (id == SYS_ID_AA64PFR1_EL1) {
>> -		val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
>> +		if (!vcpu->kvm->arch.mte_enabled)
>> +			val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
>>   	} else if (id == SYS_ID_AA64ISAR1_EL1 && !vcpu_has_ptrauth(vcpu)) {
>>   		val &= ~((0xfUL << ID_AA64ISAR1_APA_SHIFT) |
>>   			 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
>> @@ -1394,6 +1395,9 @@ static bool access_mte_regs(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>>   static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
>>   				   const struct sys_reg_desc *rd)
>>   {
>> +	if (vcpu->kvm->arch.mte_enabled)
>> +		return 0;
>> +
>>   	return REG_HIDDEN_USER | REG_HIDDEN_GUEST;
>>   }
>>   
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index f6d86033c4fa..87678ed82ab4 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1035,6 +1035,7 @@ struct kvm_ppc_resize_hpt {
>>   #define KVM_CAP_LAST_CPU 184
>>   #define KVM_CAP_SMALLER_MAXPHYADDR 185
>>   #define KVM_CAP_S390_DIAG318 186
>> +#define KVM_CAP_ARM_MTE 188
>>   
>>   #ifdef KVM_CAP_IRQ_ROUTING
>>   
>> -- 
>> 2.20.1
>>
>>
> 
> Besides the helper suggestion nit
> 
> Reviewed-by: Andrew Jones <drjones@redhat.com>
>
Andrew Jones Oct. 2, 2020, 4:20 p.m. UTC | #3
On Fri, Oct 02, 2020 at 04:30:47PM +0100, Steven Price wrote:
> On 02/10/2020 15:30, Andrew Jones wrote:
> > On Fri, Sep 25, 2020 at 10:36:07AM +0100, Steven Price wrote:
> > > +	if (system_supports_mte() && kvm->arch.mte_enabled && pfn_valid(pfn)) {
> > 
> > 'system_supports_mte() && kvm->arch.mte_enabled' is redundant, but I
> > assume system_supports_mte() is there to improve the efficiency of the
> > branch, as it's using cpus_have_const_cap().
> 
> system_supports_mte() compiles to 0 when MTE support isn't built in, so this
> code can be removed by the compiler,

I know. That's what I meant by "improve the efficiency of the branch"


> whereas with kvm->arch.mte_enabled I
> doubt the compiler can deduce that it is never set.
> 
> > Maybe a helper like
> > 
> >   static inline bool kvm_arm_mte_enabled(struct kvm *kvm)
> >   {
> >     return system_supports_mte() && kvm->arch.mte_enabled;
> >   }
> > 
> > would allow both the more efficient branch and look less confusing
> > where it gets used.
> 
> I wasn't sure it was worth having a helper since this was the only place
> checking this condition. It's also a bit tricky putting this in a logical
> header file, kvm_host.h doesn't work because struct kvm hasn't been defined
> by then.

OK, but I feel like we're setting ourselves up to revisit these types of
conditions again when our memories fade or when new developers see them
for the first time and ask.

Thanks,
drew

> 
> Steve
> 
> > > +		/*
> > > +		 * VM will be able to see the page's tags, so we must ensure
> > > +		 * they have been initialised.
> > > +		 */
> > > +		struct page *page = pfn_to_page(pfn);
> > > +		long i, nr_pages = compound_nr(page);
> > > +
> > > +		/* if PG_mte_tagged is set, tags have already been initialised */
> > > +		for (i = 0; i < nr_pages; i++, page++) {
> > > +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> > > +				mte_clear_page_tags(page_address(page));
> > > +		}
> > > +	}
> > > +
> > >   	if (writable)
> > >   		kvm_set_pfn_dirty(pfn);
> > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > > index a655f172b5ad..5010a47152b4 100644
> > > --- a/arch/arm64/kvm/sys_regs.c
> > > +++ b/arch/arm64/kvm/sys_regs.c
> > > @@ -1132,7 +1132,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
> > >   			val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
> > >   		val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT);
> > >   	} else if (id == SYS_ID_AA64PFR1_EL1) {
> > > -		val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
> > > +		if (!vcpu->kvm->arch.mte_enabled)
> > > +			val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
> > >   	} else if (id == SYS_ID_AA64ISAR1_EL1 && !vcpu_has_ptrauth(vcpu)) {
> > >   		val &= ~((0xfUL << ID_AA64ISAR1_APA_SHIFT) |
> > >   			 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
> > > @@ -1394,6 +1395,9 @@ static bool access_mte_regs(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> > >   static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> > >   				   const struct sys_reg_desc *rd)
> > >   {
> > > +	if (vcpu->kvm->arch.mte_enabled)
> > > +		return 0;
> > > +
> > >   	return REG_HIDDEN_USER | REG_HIDDEN_GUEST;
> > >   }
> > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > > index f6d86033c4fa..87678ed82ab4 100644
> > > --- a/include/uapi/linux/kvm.h
> > > +++ b/include/uapi/linux/kvm.h
> > > @@ -1035,6 +1035,7 @@ struct kvm_ppc_resize_hpt {
> > >   #define KVM_CAP_LAST_CPU 184
> > >   #define KVM_CAP_SMALLER_MAXPHYADDR 185
> > >   #define KVM_CAP_S390_DIAG318 186
> > > +#define KVM_CAP_ARM_MTE 188
> > >   #ifdef KVM_CAP_IRQ_ROUTING
> > > -- 
> > > 2.20.1
> > > 
> > > 
> > 
> > Besides the helper suggestion nit
> > 
> > Reviewed-by: Andrew Jones <drjones@redhat.com>
> > 
> 
>
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 49a55be2b9a2..4923a566ae6e 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -79,6 +79,9 @@  static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
 	    vcpu_el1_is_32bit(vcpu))
 		vcpu->arch.hcr_el2 |= HCR_TID2;
+
+	if (vcpu->kvm->arch.mte_enabled)
+		vcpu->arch.hcr_el2 |= HCR_ATA;
 }
 
 static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 4f4360dd149e..1379300c1487 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -110,6 +110,9 @@  struct kvm_arch {
 	 * supported.
 	 */
 	bool return_nisv_io_abort_to_user;
+
+	/* Memory Tagging Extension enabled for the guest */
+	bool mte_enabled;
 };
 
 struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 46dc3d75cf13..624edca0a1fa 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -87,6 +87,12 @@  int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		r = 0;
 		kvm->arch.return_nisv_io_abort_to_user = true;
 		break;
+	case KVM_CAP_ARM_MTE:
+		if (!system_supports_mte() || kvm->created_vcpus)
+			return -EINVAL;
+		r = 0;
+		kvm->arch.mte_enabled = true;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -206,6 +212,9 @@  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 */
 		r = 1;
 		break;
+	case KVM_CAP_ARM_MTE:
+		r = system_supports_mte();
+		break;
 	default:
 		r = kvm_arch_vm_ioctl_check_extension(kvm, ext);
 		break;
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index ba00bcc0c884..befb9e1f0aa6 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1949,6 +1949,21 @@  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (vma_pagesize == PAGE_SIZE && !force_pte)
 		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
 							   &pfn, &fault_ipa);
+	if (system_supports_mte() && kvm->arch.mte_enabled && pfn_valid(pfn)) {
+		/*
+		 * VM will be able to see the page's tags, so we must ensure
+		 * they have been initialised.
+		 */
+		struct page *page = pfn_to_page(pfn);
+		long i, nr_pages = compound_nr(page);
+
+		/* if PG_mte_tagged is set, tags have already been initialised */
+		for (i = 0; i < nr_pages; i++, page++) {
+			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
+				mte_clear_page_tags(page_address(page));
+		}
+	}
+
 	if (writable)
 		kvm_set_pfn_dirty(pfn);
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index a655f172b5ad..5010a47152b4 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1132,7 +1132,8 @@  static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 			val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
 		val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT);
 	} else if (id == SYS_ID_AA64PFR1_EL1) {
-		val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
+		if (!vcpu->kvm->arch.mte_enabled)
+			val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
 	} else if (id == SYS_ID_AA64ISAR1_EL1 && !vcpu_has_ptrauth(vcpu)) {
 		val &= ~((0xfUL << ID_AA64ISAR1_APA_SHIFT) |
 			 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
@@ -1394,6 +1395,9 @@  static bool access_mte_regs(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
 {
+	if (vcpu->kvm->arch.mte_enabled)
+		return 0;
+
 	return REG_HIDDEN_USER | REG_HIDDEN_GUEST;
 }
 
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index f6d86033c4fa..87678ed82ab4 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1035,6 +1035,7 @@  struct kvm_ppc_resize_hpt {
 #define KVM_CAP_LAST_CPU 184
 #define KVM_CAP_SMALLER_MAXPHYADDR 185
 #define KVM_CAP_S390_DIAG318 186
+#define KVM_CAP_ARM_MTE 188
 
 #ifdef KVM_CAP_IRQ_ROUTING