Hello Steven, On Wed, Aug 21, 2024 at 04:38:22PM +0100, Steven Price wrote: > At runtime if the realm guest accesses memory which hasn't yet been > mapped then KVM needs to either populate the region or fault the guest. > > For memory in the lower (protected) region of IPA a fresh page is > provided to the RMM which will zero the contents. For memory in the > upper (shared) region of IPA, the memory from the memslot is mapped > into the realm VM non secure. > > Signed-off-by: Steven Price <steven.price@xxxxxxx> > --- > Changes since v2: > * Avoid leaking memory if failing to map it in the realm. > * Correctly mask RTT based on LPA2 flag (see rtt_get_phys()). > * Adapt to changes in previous patches. > --- > arch/arm64/include/asm/kvm_emulate.h | 10 ++ > arch/arm64/include/asm/kvm_rme.h | 10 ++ > arch/arm64/kvm/mmu.c | 120 +++++++++++++++- > arch/arm64/kvm/rme.c | 205 +++++++++++++++++++++++++-- > 4 files changed, 325 insertions(+), 20 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h > index 7430c77574e3..0b50572d3719 100644 > --- a/arch/arm64/include/asm/kvm_emulate.h > +++ b/arch/arm64/include/asm/kvm_emulate.h > @@ -710,6 +710,16 @@ static inline bool kvm_realm_is_created(struct kvm *kvm) > return kvm_is_realm(kvm) && kvm_realm_state(kvm) != REALM_STATE_NONE; > } > > +static inline gpa_t kvm_gpa_stolen_bits(struct kvm *kvm) > +{ > + if (kvm_is_realm(kvm)) { > + struct realm *realm = &kvm->arch.realm; > + > + return BIT(realm->ia_bits - 1); > + } > + return 0; > +} > + > static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu) > { > if (static_branch_unlikely(&kvm_rme_is_available)) > diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h > index 0e44b20cfa48..c50854f44674 100644 > --- a/arch/arm64/include/asm/kvm_rme.h > +++ b/arch/arm64/include/asm/kvm_rme.h > @@ -103,6 +103,16 @@ void kvm_realm_unmap_range(struct kvm *kvm, > unsigned long ipa, > u64 size, > bool unmap_private); > +int realm_map_protected(struct realm *realm, > + unsigned long base_ipa, > + struct page *dst_page, > + unsigned long map_size, > + struct kvm_mmu_memory_cache *memcache); > +int realm_map_non_secure(struct realm *realm, > + unsigned long ipa, > + struct page *page, > + unsigned long map_size, > + struct kvm_mmu_memory_cache *memcache); > int realm_set_ipa_state(struct kvm_vcpu *vcpu, > unsigned long addr, unsigned long end, > unsigned long ripas, > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 620d26810019..eb8b8d013f3e 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -325,8 +325,13 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 > > lockdep_assert_held_write(&kvm->mmu_lock); > WARN_ON(size & ~PAGE_MASK); > - WARN_ON(stage2_apply_range(mmu, start, end, kvm_pgtable_stage2_unmap, > - may_block)); > + > + if (kvm_is_realm(kvm)) > + kvm_realm_unmap_range(kvm, start, size, !only_shared); > + else > + WARN_ON(stage2_apply_range(mmu, start, end, > + kvm_pgtable_stage2_unmap, > + may_block)); > } > > void kvm_stage2_unmap_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size) > @@ -345,7 +350,10 @@ static void stage2_flush_memslot(struct kvm *kvm, > phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT; > phys_addr_t end = addr + PAGE_SIZE * memslot->npages; > > - kvm_stage2_flush_range(&kvm->arch.mmu, addr, end); > + if (kvm_is_realm(kvm)) > + kvm_realm_unmap_range(kvm, addr, end - addr, false); > + else > + kvm_stage2_flush_range(&kvm->arch.mmu, addr, end); > } > > /** > @@ -1037,6 +1045,10 @@ void stage2_unmap_vm(struct kvm *kvm) > struct kvm_memory_slot *memslot; > int idx, bkt; > > + /* For realms this is handled by the RMM so nothing to do here */ > + if (kvm_is_realm(kvm)) > + return; > + > idx = srcu_read_lock(&kvm->srcu); > mmap_read_lock(current->mm); > write_lock(&kvm->mmu_lock); > @@ -1062,6 +1074,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) > if (kvm_is_realm(kvm) && > (kvm_realm_state(kvm) != REALM_STATE_DEAD && > kvm_realm_state(kvm) != REALM_STATE_NONE)) { > + kvm_stage2_unmap_range(mmu, 0, (~0ULL) & PAGE_MASK); > write_unlock(&kvm->mmu_lock); > kvm_realm_destroy_rtts(kvm, pgt->ia_bits); > return; > @@ -1428,6 +1441,71 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma) > return vma->vm_flags & VM_MTE_ALLOWED; > } > > +static int realm_map_ipa(struct kvm *kvm, phys_addr_t ipa, > + kvm_pfn_t pfn, unsigned long map_size, > + enum kvm_pgtable_prot prot, > + struct kvm_mmu_memory_cache *memcache) > +{ > + struct realm *realm = &kvm->arch.realm; > + struct page *page = pfn_to_page(pfn); > + > + if (WARN_ON(!(prot & KVM_PGTABLE_PROT_W))) > + return -EFAULT; > + > + if (!realm_is_addr_protected(realm, ipa)) > + return realm_map_non_secure(realm, ipa, page, map_size, > + memcache); > + > + return realm_map_protected(realm, ipa, page, map_size, memcache); > +} > + > +static int private_memslot_fault(struct kvm_vcpu *vcpu, > + phys_addr_t fault_ipa, > + struct kvm_memory_slot *memslot) > +{ > + struct kvm *kvm = vcpu->kvm; > + gpa_t gpa_stolen_mask = kvm_gpa_stolen_bits(kvm); > + gfn_t gfn = (fault_ipa & ~gpa_stolen_mask) >> PAGE_SHIFT; > + bool is_priv_gfn = !((fault_ipa & gpa_stolen_mask) == gpa_stolen_mask); > + bool priv_exists = kvm_mem_is_private(kvm, gfn); > + struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache; > + kvm_pfn_t pfn; > + int ret; > + > + if (priv_exists != is_priv_gfn) { > + kvm_prepare_memory_fault_exit(vcpu, > + fault_ipa & ~gpa_stolen_mask, > + PAGE_SIZE, > + kvm_is_write_fault(vcpu), > + false, is_priv_gfn); > + > + return 0; > + } If I understand correctly, `kvm_prepare_memory_fault_exit()` ends up returning to the VMM with the KVM_EXIT_MEMORY_FAULT exit reason. The documentation says (https://docs.kernel.org/virt/kvm/api.html#kvm-run): "Note! KVM_EXIT_MEMORY_FAULT is unique among all KVM exit reasons in that it accompanies a return code of ‘-1’, not ‘0’! errno will always be set to EFAULT or EHWPOISON when KVM exits with KVM_EXIT_MEMORY_FAULT, userspace should assume kvm_run.exit_reason is stale/undefined for all other error numbers." Shall the return code be different for KVM_EXIT_MEMORY_FAULT? Thanks, Matias. > + > + if (!is_priv_gfn) { > + /* Not a private mapping, handling normally */ > + return -EAGAIN; > + } > + > + ret = kvm_mmu_topup_memory_cache(memcache, > + kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu)); > + if (ret) > + return ret; > + > + ret = kvm_gmem_get_pfn(kvm, memslot, gfn, &pfn, NULL); > + if (ret) > + return ret; > + > + /* FIXME: Should be able to use bigger than PAGE_SIZE mappings */ > + ret = realm_map_ipa(kvm, fault_ipa, pfn, PAGE_SIZE, KVM_PGTABLE_PROT_W, > + memcache); > + if (!ret) > + return 1; /* Handled */ > + > + put_page(pfn_to_page(pfn)); > + return ret; > +} > + > static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > struct kvm_s2_trans *nested, > struct kvm_memory_slot *memslot, unsigned long hva, > @@ -1449,10 +1527,19 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > long vma_pagesize, fault_granule; > enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; > struct kvm_pgtable *pgt; > + gpa_t gpa_stolen_mask = kvm_gpa_stolen_bits(vcpu->kvm); > > if (fault_is_perm) > fault_granule = kvm_vcpu_trap_get_perm_fault_granule(vcpu); > write_fault = kvm_is_write_fault(vcpu); > + > + /* > + * Realms cannot map protected pages read-only > + * FIXME: It should be possible to map unprotected pages read-only > + */ > + if (vcpu_is_rec(vcpu)) > + write_fault = true; > + > exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu); > VM_BUG_ON(write_fault && exec_fault); > > @@ -1553,7 +1640,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE) > fault_ipa &= ~(vma_pagesize - 1); > > - gfn = ipa >> PAGE_SHIFT; > + gfn = (ipa & ~gpa_stolen_mask) >> PAGE_SHIFT; > mte_allowed = kvm_vma_mte_allowed(vma); > > vfio_allow_any_uc = vma->vm_flags & VM_ALLOW_ANY_UNCACHED; > @@ -1634,7 +1721,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > * If we are not forced to use page mapping, check if we are > * backed by a THP and thus use block mapping if possible. > */ > - if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) { > + /* FIXME: We shouldn't need to disable this for realms */ > + if (vma_pagesize == PAGE_SIZE && !(force_pte || device || kvm_is_realm(kvm))) { > if (fault_is_perm && fault_granule > PAGE_SIZE) > vma_pagesize = fault_granule; > else > @@ -1686,6 +1774,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > */ > prot &= ~KVM_NV_GUEST_MAP_SZ; > ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot); > + } else if (kvm_is_realm(kvm)) { > + ret = realm_map_ipa(kvm, fault_ipa, pfn, vma_pagesize, > + prot, memcache); > } else { > ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize, > __pfn_to_phys(pfn), prot, > @@ -1744,6 +1835,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) > struct kvm_memory_slot *memslot; > unsigned long hva; > bool is_iabt, write_fault, writable; > + gpa_t gpa_stolen_mask = kvm_gpa_stolen_bits(vcpu->kvm); > gfn_t gfn; > int ret, idx; > > @@ -1834,8 +1926,15 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) > nested = &nested_trans; > } > > - gfn = ipa >> PAGE_SHIFT; > + gfn = (ipa & ~gpa_stolen_mask) >> PAGE_SHIFT; > memslot = gfn_to_memslot(vcpu->kvm, gfn); > + > + if (kvm_slot_can_be_private(memslot)) { > + ret = private_memslot_fault(vcpu, fault_ipa, memslot); > + if (ret != -EAGAIN) > + goto out; > + } > + > hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable); > write_fault = kvm_is_write_fault(vcpu); > if (kvm_is_error_hva(hva) || (write_fault && !writable)) { > @@ -1879,6 +1978,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) > * of the page size. > */ > ipa |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0); > + ipa &= ~gpa_stolen_mask; > ret = io_mem_abort(vcpu, ipa); > goto out_unlock; > } > @@ -1927,6 +2027,10 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) > if (!kvm->arch.mmu.pgt) > return false; > > + /* We don't support aging for Realms */ > + if (kvm_is_realm(kvm)) > + return true; > + > return kvm_pgtable_stage2_test_clear_young(kvm->arch.mmu.pgt, > range->start << PAGE_SHIFT, > size, true); > @@ -1943,6 +2047,10 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) > if (!kvm->arch.mmu.pgt) > return false; > > + /* We don't support aging for Realms */ > + if (kvm_is_realm(kvm)) > + return true; > + > return kvm_pgtable_stage2_test_clear_young(kvm->arch.mmu.pgt, > range->start << PAGE_SHIFT, > size, false); > diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c > index 2c4e28b457be..337b3dd1e00c 100644 > --- a/arch/arm64/kvm/rme.c > +++ b/arch/arm64/kvm/rme.c > @@ -627,6 +627,181 @@ static int fold_rtt(struct realm *realm, unsigned long addr, int level) > return 0; > } > > +static phys_addr_t rtt_get_phys(struct realm *realm, struct rtt_entry *rtt) > +{ > + bool lpa2 = realm->params->flags & RMI_REALM_PARAM_FLAG_LPA2; > + > + if (lpa2) > + return rtt->desc & GENMASK(49, 12); > + return rtt->desc & GENMASK(47, 12); > +} > + > +int realm_map_protected(struct realm *realm, > + unsigned long base_ipa, > + struct page *dst_page, > + unsigned long map_size, > + struct kvm_mmu_memory_cache *memcache) > +{ > + phys_addr_t dst_phys = page_to_phys(dst_page); > + phys_addr_t rd = virt_to_phys(realm->rd); > + unsigned long phys = dst_phys; > + unsigned long ipa = base_ipa; > + unsigned long size; > + int map_level; > + int ret = 0; > + > + if (WARN_ON(!IS_ALIGNED(ipa, map_size))) > + return -EINVAL; > + > + switch (map_size) { > + case PAGE_SIZE: > + map_level = 3; > + break; > + case RME_L2_BLOCK_SIZE: > + map_level = 2; > + break; > + default: > + return -EINVAL; > + } > + > + if (map_level < RME_RTT_MAX_LEVEL) { > + /* > + * A temporary RTT is needed during the map, precreate it, > + * however if there is an error (e.g. missing parent tables) > + * this will be handled below. > + */ > + realm_create_rtt_levels(realm, ipa, map_level, > + RME_RTT_MAX_LEVEL, memcache); > + } > + > + for (size = 0; size < map_size; size += PAGE_SIZE) { > + if (rmi_granule_delegate(phys)) { > + struct rtt_entry rtt; > + > + /* > + * It's possible we raced with another VCPU on the same > + * fault. If the entry exists and matches then exit > + * early and assume the other VCPU will handle the > + * mapping. > + */ > + if (rmi_rtt_read_entry(rd, ipa, RME_RTT_MAX_LEVEL, &rtt)) > + goto err; > + > + /* > + * FIXME: For a block mapping this could race at level > + * 2 or 3... currently we don't support block mappings > + */ > + if (WARN_ON((rtt.walk_level != RME_RTT_MAX_LEVEL || > + rtt.state != RMI_ASSIGNED || > + rtt_get_phys(realm, &rtt) != phys))) { > + goto err; > + } > + > + return 0; > + } > + > + ret = rmi_data_create_unknown(rd, phys, ipa); > + > + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) { > + /* Create missing RTTs and retry */ > + int level = RMI_RETURN_INDEX(ret); > + > + ret = realm_create_rtt_levels(realm, ipa, level, > + RME_RTT_MAX_LEVEL, > + memcache); > + WARN_ON(ret); > + if (ret) > + goto err_undelegate; > + > + ret = rmi_data_create_unknown(rd, phys, ipa); > + } > + WARN_ON(ret); > + > + if (ret) > + goto err_undelegate; > + > + phys += PAGE_SIZE; > + ipa += PAGE_SIZE; > + } > + > + if (map_size == RME_L2_BLOCK_SIZE) > + ret = fold_rtt(realm, base_ipa, map_level); > + if (WARN_ON(ret)) > + goto err; > + > + return 0; > + > +err_undelegate: > + if (WARN_ON(rmi_granule_undelegate(phys))) { > + /* Page can't be returned to NS world so is lost */ > + get_page(phys_to_page(phys)); > + } > +err: > + while (size > 0) { > + unsigned long data, top; > + > + phys -= PAGE_SIZE; > + size -= PAGE_SIZE; > + ipa -= PAGE_SIZE; > + > + WARN_ON(rmi_data_destroy(rd, ipa, &data, &top)); > + > + if (WARN_ON(rmi_granule_undelegate(phys))) { > + /* Page can't be returned to NS world so is lost */ > + get_page(phys_to_page(phys)); > + } > + } > + return -ENXIO; > +} > + > +int realm_map_non_secure(struct realm *realm, > + unsigned long ipa, > + struct page *page, > + unsigned long map_size, > + struct kvm_mmu_memory_cache *memcache) > +{ > + phys_addr_t rd = virt_to_phys(realm->rd); > + int map_level; > + int ret = 0; > + unsigned long desc = page_to_phys(page) | > + PTE_S2_MEMATTR(MT_S2_FWB_NORMAL) | > + /* FIXME: Read+Write permissions for now */ > + (3 << 6) | > + PTE_SHARED; > + > + if (WARN_ON(!IS_ALIGNED(ipa, map_size))) > + return -EINVAL; > + > + switch (map_size) { > + case PAGE_SIZE: > + map_level = 3; > + break; > + case RME_L2_BLOCK_SIZE: > + map_level = 2; > + break; > + default: > + return -EINVAL; > + } > + > + ret = rmi_rtt_map_unprotected(rd, ipa, map_level, desc); > + > + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) { > + /* Create missing RTTs and retry */ > + int level = RMI_RETURN_INDEX(ret); > + > + ret = realm_create_rtt_levels(realm, ipa, level, map_level, > + memcache); > + if (WARN_ON(ret)) > + return -ENXIO; > + > + ret = rmi_rtt_map_unprotected(rd, ipa, map_level, desc); > + } > + if (WARN_ON(ret)) > + return -ENXIO; > + > + return 0; > +} > + > static int populate_par_region(struct kvm *kvm, > phys_addr_t ipa_base, > phys_addr_t ipa_end, > @@ -638,7 +813,6 @@ static int populate_par_region(struct kvm *kvm, > int idx; > phys_addr_t ipa; > int ret = 0; > - struct page *tmp_page; > unsigned long data_flags = 0; > > base_gfn = gpa_to_gfn(ipa_base); > @@ -660,9 +834,8 @@ static int populate_par_region(struct kvm *kvm, > goto out; > } > > - tmp_page = alloc_page(GFP_KERNEL); > - if (!tmp_page) { > - ret = -ENOMEM; > + if (!kvm_slot_can_be_private(memslot)) { > + ret = -EINVAL; > goto out; > } > > @@ -729,28 +902,32 @@ static int populate_par_region(struct kvm *kvm, > for (offset = 0; offset < map_size && !ret; > offset += PAGE_SIZE, page++) { > phys_addr_t page_ipa = ipa + offset; > + kvm_pfn_t priv_pfn; > + int order; > + > + ret = kvm_gmem_get_pfn(kvm, memslot, > + page_ipa >> PAGE_SHIFT, > + &priv_pfn, &order); > + if (ret) > + break; > > ret = realm_create_protected_data_page(realm, page_ipa, > - page, tmp_page, > - data_flags); > + pfn_to_page(priv_pfn), > + page, data_flags); > } > + > + kvm_release_pfn_clean(pfn); > + > if (ret) > - goto err_release_pfn; > + break; > > if (level == 2) > fold_rtt(realm, ipa, level); > > ipa += map_size; > - kvm_release_pfn_dirty(pfn); > -err_release_pfn: > - if (ret) { > - kvm_release_pfn_clean(pfn); > - break; > - } > } > > mmap_read_unlock(current->mm); > - __free_page(tmp_page); > > out: > srcu_read_unlock(&kvm->srcu, idx); > -- > 2.34.1 > >