Re: [PATCH v12 01/84] KVM: arm64: Release pfn, i.e. put page, if copying MTE tags hits ZONE_DEVICE

Marc Zyngier
2024-08-01T10:08:40Z

+ Steven Price for this patch (and the following one), as this really
is his turf.

On Sat, 27 Jul 2024 00:51:10 +0100,
Sean Christopherson <seanjc@google.com> wrote:
>
> Put the page reference acquired by gfn_to_pfn_prot() if
> kvm_vm_ioctl_mte_copy_tags() runs into ZONE_DEVICE memory. KVM's less-
> than-stellar heuristics for dealing with pfn-mapped memory means that KVM
> can get a page reference to ZONE_DEVICE memory.
>
> Fixes: f0376edb1ddc ("KVM: arm64: Add ioctl to fetch/store tags in a guest")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/arm64/kvm/guest.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 11098eb7eb44..e1f0ff08836a 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -1059,6 +1059,7 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> page = pfn_to_online_page(pfn);
> if (!page) {
> /* Reject ZONE_DEVICE memory */
> + kvm_release_pfn_clean(pfn);
> ret = -EFAULT;
> goto out;
> }
> --
> 2.46.0.rc1.232.g9752f9e123-goog
>
>

--
Without deviation from the norm, progress is not possible.