| Message ID | 20210726153552.1535838-3-maz@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Remove kvm_is_transparent_hugepage() and friends | expand |
Hi Marc, On 7/26/21 4:35 PM, Marc Zyngier wrote: > We currently rely on the kvm_is_transparent_hugepage() helper to > discover whether a given page has the potential to be mapped as > a block mapping. > > However, this API doesn't really give un everything we want: > - we don't get the size: this is not crucial today as we only > support PMD-sized THPs, but we'd like to have larger sizes > in the future > - we're the only user left of the API, and there is a will > to remove it altogether > > To address the above, implement a simple walker using the existing > page table infrastructure, and plumb it into transparent_hugepage_adjust(). > No new page sizes are supported in the process. > > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > arch/arm64/kvm/mmu.c | 34 ++++++++++++++++++++++++++++++---- > 1 file changed, 30 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 3155c9e778f0..0adc1617c557 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -433,6 +433,32 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size, > return 0; > } > > +static struct kvm_pgtable_mm_ops kvm_user_mm_ops = { > + /* We shouldn't need any other callback to walk the PT */ That looks correct to me, mm_ops is used in __kvm_pgtable_visit(), and then only the phys_to_virt field callback is used. kvm_host_va() is also the callback used by kvm_s2_mm_ops, which looks right to me. > + .phys_to_virt = kvm_host_va, > +}; > + > +static int get_user_mapping_size(struct kvm *kvm, u64 addr) > +{ > + struct kvm_pgtable pgt = { > + .pgd = (kvm_pte_t *)kvm->mm->pgd, > + .ia_bits = VA_BITS, > + .start_level = (KVM_PGTABLE_MAX_LEVELS - > + CONFIG_PGTABLE_LEVELS), > + .mm_ops = &kvm_user_mm_ops, > + }; > + kvm_pte_t pte = 0; /* Keep GCC quiet... */ > + u32 level = ~0; > + int ret; > + > + ret = kvm_pgtable_get_leaf(&pgt, addr, &pte, &level); > + VM_BUG_ON(ret); > + VM_BUG_ON(level >= KVM_PGTABLE_MAX_LEVELS); > + VM_BUG_ON(!(pte & PTE_VALID)); > + > + return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level)); > +} > + > static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = { > .zalloc_page = stage2_memcache_zalloc_page, > .zalloc_pages_exact = kvm_host_zalloc_pages_exact, > @@ -780,7 +806,7 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot, > * Returns the size of the mapping. > */ > static unsigned long > -transparent_hugepage_adjust(struct kvm_memory_slot *memslot, > +transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot, > unsigned long hva, kvm_pfn_t *pfnp, > phys_addr_t *ipap) > { > @@ -791,8 +817,8 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot, > * sure that the HVA and IPA are sufficiently aligned and that the > * block map is contained within the memslot. > */ > - if (kvm_is_transparent_hugepage(pfn) && > - fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) { > + if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) && > + get_user_mapping_size(kvm, hva) >= PMD_SIZE) { > /* > * The address we faulted on is backed by a transparent huge > * page. However, because we map the compound huge page and > @@ -1051,7 +1077,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > * backed by a THP and thus use block mapping if possible. > */ > if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) > - vma_pagesize = transparent_hugepage_adjust(memslot, hva, > + vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva, > &pfn, &fault_ipa); > > if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) { Sean explained well why holding the mmap lock isn't needed here. The patch looks correct to me: Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com> Thanks, Alex
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 3155c9e778f0..0adc1617c557 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -433,6 +433,32 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size, return 0; } +static struct kvm_pgtable_mm_ops kvm_user_mm_ops = { + /* We shouldn't need any other callback to walk the PT */ + .phys_to_virt = kvm_host_va, +}; + +static int get_user_mapping_size(struct kvm *kvm, u64 addr) +{ + struct kvm_pgtable pgt = { + .pgd = (kvm_pte_t *)kvm->mm->pgd, + .ia_bits = VA_BITS, + .start_level = (KVM_PGTABLE_MAX_LEVELS - + CONFIG_PGTABLE_LEVELS), + .mm_ops = &kvm_user_mm_ops, + }; + kvm_pte_t pte = 0; /* Keep GCC quiet... */ + u32 level = ~0; + int ret; + + ret = kvm_pgtable_get_leaf(&pgt, addr, &pte, &level); + VM_BUG_ON(ret); + VM_BUG_ON(level >= KVM_PGTABLE_MAX_LEVELS); + VM_BUG_ON(!(pte & PTE_VALID)); + + return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level)); +} + static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = { .zalloc_page = stage2_memcache_zalloc_page, .zalloc_pages_exact = kvm_host_zalloc_pages_exact, @@ -780,7 +806,7 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot, * Returns the size of the mapping. */ static unsigned long -transparent_hugepage_adjust(struct kvm_memory_slot *memslot, +transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot, unsigned long hva, kvm_pfn_t *pfnp, phys_addr_t *ipap) { @@ -791,8 +817,8 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot, * sure that the HVA and IPA are sufficiently aligned and that the * block map is contained within the memslot. */ - if (kvm_is_transparent_hugepage(pfn) && - fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) { + if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) && + get_user_mapping_size(kvm, hva) >= PMD_SIZE) { /* * The address we faulted on is backed by a transparent huge * page. However, because we map the compound huge page and @@ -1051,7 +1077,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, * backed by a THP and thus use block mapping if possible. */ if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) - vma_pagesize = transparent_hugepage_adjust(memslot, hva, + vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva, &pfn, &fault_ipa); if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
We currently rely on the kvm_is_transparent_hugepage() helper to discover whether a given page has the potential to be mapped as a block mapping. However, this API doesn't really give un everything we want: - we don't get the size: this is not crucial today as we only support PMD-sized THPs, but we'd like to have larger sizes in the future - we're the only user left of the API, and there is a will to remove it altogether To address the above, implement a simple walker using the existing page table infrastructure, and plumb it into transparent_hugepage_adjust(). No new page sizes are supported in the process. Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/kvm/mmu.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-)