From: Steven Price <steven.price@arm.com>
To: Peter Collingbourne <pcc@google.com>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Cornelia Huck <cohuck@redhat.com>, Will Deacon <will@kernel.org>,
Marc Zyngier <maz@kernel.org>,
Evgenii Stepanov <eugenis@google.com>,
kvm@vger.kernel.org,
Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: Re: [PATCH v3 2/7] KVM: arm64: Simplify the sanitise_mte_tags() logic
Date: Fri, 2 Sep 2022 15:47:30 +0100 [thread overview]
Message-ID: <54b979fc-5cb3-6eb4-47d4-e07e99359db9@arm.com> (raw)
In-Reply-To: <20220810193033.1090251-3-pcc@google.com>
On 10/08/2022 20:30, Peter Collingbourne wrote:
> From: Catalin Marinas <catalin.marinas@arm.com>
>
> 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@arm.com>
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Peter Collingbourne <pcc@google.com>
> ---
> 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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next prev parent reply other threads:[~2022-09-02 14:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-10 19:30 [PATCH v3 0/7] KVM: arm64: permit MAP_SHARED mappings with MTE enabled Peter Collingbourne
2022-08-10 19:30 ` [PATCH v3 1/7] arm64: mte: Fix/clarify the PG_mte_tagged semantics Peter Collingbourne
2022-09-01 15:49 ` Catalin Marinas
2022-09-02 10:26 ` Cornelia Huck
2022-09-02 14:47 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 2/7] KVM: arm64: Simplify the sanitise_mte_tags() logic Peter Collingbourne
2022-09-02 14:47 ` Steven Price [this message]
2022-08-10 19:30 ` [PATCH v3 3/7] mm: Add PG_arch_3 page flag Peter Collingbourne
2022-08-11 7:16 ` kernel test robot
2022-09-01 17:59 ` Catalin Marinas
2022-09-05 17:01 ` Catalin Marinas
2022-09-19 18:12 ` Marc Zyngier
2022-09-20 15:39 ` Catalin Marinas
2022-09-20 16:33 ` Marc Zyngier
2022-09-20 16:58 ` Catalin Marinas
2022-09-21 3:53 ` Peter Collingbourne
2022-08-10 19:30 ` [PATCH v3 4/7] arm64: mte: Lock a page for MTE tag initialisation Peter Collingbourne
2022-09-02 14:47 ` Steven Price
2022-09-02 16:28 ` Catalin Marinas
2022-09-02 16:58 ` Catalin Marinas
2022-09-05 7:37 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 5/7] KVM: arm64: unify the tests for VMAs in memslots when MTE is enabled Peter Collingbourne
2022-09-02 13:41 ` Catalin Marinas
2022-09-02 14:47 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 6/7] KVM: arm64: permit all VM_MTE_ALLOWED mappings with MTE enabled Peter Collingbourne
2022-09-02 13:45 ` Catalin Marinas
2022-09-02 14:47 ` Steven Price
2022-09-12 16:23 ` Marc Zyngier
2022-09-13 4:10 ` Peter Collingbourne
2022-08-10 19:30 ` [PATCH v3 7/7] Documentation: document the ABI changes for KVM_CAP_ARM_MTE Peter Collingbourne
2022-09-02 13:49 ` Catalin Marinas
2022-09-02 14:05 ` [PATCH v3 0/7] KVM: arm64: permit MAP_SHARED mappings with MTE enabled Catalin Marinas
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