On 10/08/2022 20:30, Peter Collingbourne wrote:
> From: Catalin Marinas <catalin.marinas@xxxxxxx>
>
> Currently sanitise_mte_tags() checks if it's an online page before
> attempting to sanitise the tags. Such detection should be done in the
> caller via the VM_MTE_ALLOWED vma flag. Since kvm_set_spte_gfn() does
> not have the vma, leave the page unmapped if not already tagged. Tag
> initialisation will be done on a subsequent access fault in
> user_mem_abort().
Looks correct to me.
Reviewed-by: Steven Price <steven.price@xxxxxxx>
> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: Steven Price <steven.price@xxxxxxx>
> Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
> ---
> arch/arm64/kvm/mmu.c | 40 +++++++++++++++-------------------------
> 1 file changed, 15 insertions(+), 25 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index c9012707f69c..1a3707aeb41f 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1056,23 +1056,14 @@ static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
> * - mmap_lock protects between a VM faulting a page in and the VMM performing
> * an mprotect() to add VM_MTE
> */
> -static int sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
> - unsigned long size)
> +static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
> + unsigned long size)
> {
> unsigned long i, nr_pages = size >> PAGE_SHIFT;
> - struct page *page;
> + struct page *page = pfn_to_page(pfn);
>
> if (!kvm_has_mte(kvm))
> - return 0;
> -
> - /*
> - * pfn_to_online_page() is used to reject ZONE_DEVICE pages
> - * that may not support tags.
> - */
> - page = pfn_to_online_page(pfn);
> -
> - if (!page)
> - return -EFAULT;
> + return;
>
> for (i = 0; i < nr_pages; i++, page++) {
> if (!page_mte_tagged(page)) {
> @@ -1080,8 +1071,6 @@ static int sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
> set_page_mte_tagged(page);
> }
> }
> -
> - return 0;
> }
>
> static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> @@ -1092,7 +1081,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> bool write_fault, writable, force_pte = false;
> bool exec_fault;
> bool device = false;
> - bool shared;
> unsigned long mmu_seq;
> struct kvm *kvm = vcpu->kvm;
> struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
> @@ -1142,8 +1130,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> vma_shift = get_vma_page_shift(vma, hva);
> }
>
> - shared = (vma->vm_flags & VM_SHARED);
> -
> switch (vma_shift) {
> #ifndef __PAGETABLE_PMD_FOLDED
> case PUD_SHIFT:
> @@ -1264,12 +1250,13 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>
> if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
> /* Check the VMM hasn't introduced a new VM_SHARED VMA */
> - if (!shared)
> - ret = sanitise_mte_tags(kvm, pfn, vma_pagesize);
> - else
> + if ((vma->vm_flags & VM_MTE_ALLOWED) &&
> + !(vma->vm_flags & VM_SHARED)) {
> + sanitise_mte_tags(kvm, pfn, vma_pagesize);
> + } else {
> ret = -EFAULT;
> - if (ret)
> goto out_unlock;
> + }
> }
>
> if (writable)
> @@ -1491,15 +1478,18 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
> bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> {
> kvm_pfn_t pfn = pte_pfn(range->pte);
> - int ret;
>
> if (!kvm->arch.mmu.pgt)
> return false;
>
> WARN_ON(range->end - range->start != 1);
>
> - ret = sanitise_mte_tags(kvm, pfn, PAGE_SIZE);
> - if (ret)
> + /*
> + * If the page isn't tagged, defer to user_mem_abort() for sanitising
> + * the MTE tags. The S2 pte should have been unmapped by
> + * mmu_notifier_invalidate_range_end().
> + */
> + if (kvm_has_mte(kvm) && !page_mte_tagged(pfn_to_page(pfn)))
> return false;
>
> /*
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