On Wed, 10 Aug 2022 20:30:32 +0100,
Peter Collingbourne <pcc@xxxxxxxxxx> wrote:
>
> Certain VMMs such as crosvm have features (e.g. sandboxing) that depend
> on being able to map guest memory as MAP_SHARED. The current restriction
> on sharing MAP_SHARED pages with the guest is preventing the use of
> those features with MTE. Now that the races between tasks concurrently
> clearing tags on the same page have been fixed, remove this restriction.
>
> Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx>
> ---
> arch/arm64/kvm/mmu.c | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index d54be80e31dd..fc65dc20655d 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1075,14 +1075,6 @@ static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
>
> static bool kvm_vma_mte_allowed(struct vm_area_struct *vma)
> {
> - /*
> - * VM_SHARED mappings are not allowed with MTE to avoid races
> - * when updating the PG_mte_tagged page flag, see
> - * sanitise_mte_tags for more details.
> - */
> - if (vma->vm_flags & VM_SHARED)
> - return false;
> -
> return vma->vm_flags & VM_MTE_ALLOWED;
> }
>
Can you provide a pointer to some VMM making use of this functionality
and enabling MTE? A set of crosvm patches (for example) would be
useful to evaluate this series.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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