On Mon, May 17, 2021 at 01:32:38PM +0100, Steven Price wrote:
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 24223adae150..b3edde68bc3e 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -184,6 +184,17 @@ struct kvm_vcpu_events {
> __u32 reserved[12];
> };
>
> +struct kvm_arm_copy_mte_tags {
> + __u64 guest_ipa;
> + __u64 length;
> + void __user *addr;
> + __u64 flags;
> + __u64 reserved[2];
I forgot the past discussions, what's the reserved for? Future
expansion?
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index e89a5e275e25..4b6c83beb75d 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1309,6 +1309,65 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
> }
> }
>
> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> + struct kvm_arm_copy_mte_tags *copy_tags)
> +{
> + gpa_t guest_ipa = copy_tags->guest_ipa;
> + size_t length = copy_tags->length;
> + void __user *tags = copy_tags->addr;
> + gpa_t gfn;
> + bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
> + int ret = 0;
> +
> + if (copy_tags->reserved[0] || copy_tags->reserved[1])
> + return -EINVAL;
> +
> + if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
> + return -EINVAL;
> +
> + if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
> + return -EINVAL;
> +
> + gfn = gpa_to_gfn(guest_ipa);
> +
> + mutex_lock(&kvm->slots_lock);
> +
> + while (length > 0) {
> + kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
> + void *maddr;
> + unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
> +
> + if (is_error_noslot_pfn(pfn)) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + maddr = page_address(pfn_to_page(pfn));
> +
> + if (!write) {
> + num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
> + kvm_release_pfn_clean(pfn);
Do we need to check if PG_mte_tagged is set? If the page was not faulted
into the guest address space but the VMM has the page, does the
gfn_to_pfn_prot() guarantee that a kvm_set_spte_gfn() was called? If
not, this may read stale tags.
> + } else {
> + num_tags = mte_copy_tags_from_user(maddr, tags,
> + num_tags);
> + kvm_release_pfn_dirty(pfn);
> + }
Same question here, if the we can't guarantee the stage 2 pte being set,
we'd need to set PG_mte_tagged.
> +
> + if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + gfn++;
> + tags += num_tags;
> + length -= PAGE_SIZE;
> + }
> +
> +out:
> + mutex_unlock(&kvm->slots_lock);
> + return ret;
> +}
> +
--
Catalin
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