// SPDX-License-Identifier: GPL-2.0 /* * Secure pages management: Migration of pages between normal and secure * memory of KVM guests. * * Copyright 2018 Bharata B Rao, IBM Corp. */ /* * A pseries guest can be run as secure guest on Ultravisor-enabled * POWER platforms. On such platforms, this driver will be used to manage * the movement of guest pages between the normal memory managed by * hypervisor (HV) and secure memory managed by Ultravisor (UV). * * The page-in or page-out requests from UV will come to HV as hcalls and * HV will call back into UV via ultracalls to satisfy these page requests. * * Private ZONE_DEVICE memory equal to the amount of secure memory * available in the platform for running secure guests is hotplugged. * Whenever a page belonging to the guest becomes secure, a page from this * private device memory is used to represent and track that secure page * on the HV side. Some pages (like virtio buffers, VPA pages etc) are * shared between UV and HV. However such pages aren't represented by * device private memory and mappings to shared memory exist in both * UV and HV page tables. */ /* * Notes on locking * * kvm->arch.uvmem_lock is a per-guest lock that prevents concurrent * page-in and page-out requests for the same GPA. Concurrent accesses * can either come via UV (guest vCPUs requesting for same page) * or when HV and guest simultaneously access the same page. * This mutex serializes the migration of page from HV(normal) to * UV(secure) and vice versa. So the serialization points are around * migrate_vma routines and page-in/out routines. * * Per-guest mutex comes with a cost though. Mainly it serializes the * fault path as page-out can occur when HV faults on accessing secure * guest pages. Currently UV issues page-in requests for all the guest * PFNs one at a time during early boot (UV_ESM uvcall), so this is * not a cause for concern. Also currently the number of page-outs caused * by HV touching secure pages is very very low. If an when UV supports * overcommitting, then we might see concurrent guest driven page-outs. * * Locking order * * 1. kvm->srcu - Protects KVM memslots * 2. kvm->mm->mmap_sem - find_vma, migrate_vma_pages and helpers, ksm_madvise * 3. kvm->arch.uvmem_lock - protects read/writes to uvmem slots thus acting * as sync-points for page-in/out */ /* * Notes on page size * * Currently UV uses 2MB mappings internally, but will issue H_SVM_PAGE_IN * and H_SVM_PAGE_OUT hcalls in PAGE_SIZE(64K) granularity. HV tracks * secure GPAs at 64K page size and maintains one device PFN for each * 64K secure GPA. UV_PAGE_IN and UV_PAGE_OUT calls by HV are also issued * for 64K page at a time. * * HV faulting on secure pages: When HV touches any secure page, it * faults and issues a UV_PAGE_OUT request with 64K page size. Currently * UV splits and remaps the 2MB page if necessary and copies out the * required 64K page contents. * * Shared pages: Whenever guest shares a secure page, UV will split and * remap the 2MB page if required and issue H_SVM_PAGE_IN with 64K page size. * * In summary, the current secure pages handling code in HV assumes * 64K page size and in fact fails any page-in/page-out requests of * non-64K size upfront. If and when UV starts supporting multiple * page-sizes, we need to break this assumption. */ #include #include #include #include #include #include #include static struct dev_pagemap kvmppc_uvmem_pgmap; static unsigned long *kvmppc_uvmem_bitmap; static DEFINE_SPINLOCK(kvmppc_uvmem_bitmap_lock); #define KVMPPC_UVMEM_PFN (1UL << 63) struct kvmppc_uvmem_slot { struct list_head list; unsigned long nr_pfns; unsigned long base_pfn; unsigned long *pfns; }; struct kvmppc_uvmem_page_pvt { struct kvm *kvm; unsigned long gpa; bool skip_page_out; }; int kvmppc_uvmem_slot_init(struct kvm *kvm, const struct kvm_memory_slot *slot) { struct kvmppc_uvmem_slot *p; p = kzalloc(sizeof(*p), GFP_KERNEL); if (!p) return -ENOMEM; p->pfns = vzalloc(array_size(slot->npages, sizeof(*p->pfns))); if (!p->pfns) { kfree(p); return -ENOMEM; } p->nr_pfns = slot->npages; p->base_pfn = slot->base_gfn; mutex_lock(&kvm->arch.uvmem_lock); list_add(&p->list, &kvm->arch.uvmem_pfns); mutex_unlock(&kvm->arch.uvmem_lock); return 0; } /* * All device PFNs are already released by the time we come here. */ void kvmppc_uvmem_slot_free(struct kvm *kvm, const struct kvm_memory_slot *slot) { struct kvmppc_uvmem_slot *p, *next; mutex_lock(&kvm->arch.uvmem_lock); list_for_each_entry_safe(p, next, &kvm->arch.uvmem_pfns, list) { if (p->base_pfn == slot->base_gfn) { vfree(p->pfns); list_del(&p->list); kfree(p); break; } } mutex_unlock(&kvm->arch.uvmem_lock); } static void kvmppc_uvmem_pfn_insert(unsigned long gfn, unsigned long uvmem_pfn, struct kvm *kvm) { struct kvmppc_uvmem_slot *p; list_for_each_entry(p, &kvm->arch.uvmem_pfns, list) { if (gfn >= p->base_pfn && gfn < p->base_pfn + p->nr_pfns) { unsigned long index = gfn - p->base_pfn; p->pfns[index] = uvmem_pfn | KVMPPC_UVMEM_PFN; return; } } } static void kvmppc_uvmem_pfn_remove(unsigned long gfn, struct kvm *kvm) { struct kvmppc_uvmem_slot *p; list_for_each_entry(p, &kvm->arch.uvmem_pfns, list) { if (gfn >= p->base_pfn && gfn < p->base_pfn + p->nr_pfns) { p->pfns[gfn - p->base_pfn] = 0; return; } } } static bool kvmppc_gfn_is_uvmem_pfn(unsigned long gfn, struct kvm *kvm, unsigned long *uvmem_pfn) { struct kvmppc_uvmem_slot *p; list_for_each_entry(p, &kvm->arch.uvmem_pfns, list) { if (gfn >= p->base_pfn && gfn < p->base_pfn + p->nr_pfns) { unsigned long index = gfn - p->base_pfn; if (p->pfns[index] & KVMPPC_UVMEM_PFN) { if (uvmem_pfn) *uvmem_pfn = p->pfns[index] & ~KVMPPC_UVMEM_PFN; return true; } else return false; } } return false; } unsigned long kvmppc_h_svm_init_start(struct kvm *kvm) { struct kvm_memslots *slots; struct kvm_memory_slot *memslot; int ret = H_SUCCESS; int srcu_idx; if (!kvmppc_uvmem_bitmap) return H_UNSUPPORTED; /* Only radix guests can be secure guests */ if (!kvm_is_radix(kvm)) return H_UNSUPPORTED; srcu_idx = srcu_read_lock(&kvm->srcu); slots = kvm_memslots(kvm); kvm_for_each_memslot(memslot, slots) { if (kvmppc_uvmem_slot_init(kvm, memslot)) { ret = H_PARAMETER; goto out; } ret = uv_register_mem_slot(kvm->arch.lpid, memslot->base_gfn << PAGE_SHIFT, memslot->npages * PAGE_SIZE, 0, memslot->id); if (ret < 0) { kvmppc_uvmem_slot_free(kvm, memslot); ret = H_PARAMETER; goto out; } } kvm->arch.secure_guest |= KVMPPC_SECURE_INIT_START; out: srcu_read_unlock(&kvm->srcu, srcu_idx); return ret; } unsigned long kvmppc_h_svm_init_done(struct kvm *kvm) { if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START)) return H_UNSUPPORTED; kvm->arch.secure_guest |= KVMPPC_SECURE_INIT_DONE; pr_info("LPID %d went secure\n", kvm->arch.lpid); return H_SUCCESS; } /* * Get a free device PFN from the pool * * Called when a normal page is moved to secure memory (UV_PAGE_IN). Device * PFN will be used to keep track of the secure page on HV side. * * Called with kvm->arch.uvmem_lock held */ static struct page *kvmppc_uvmem_get_page(unsigned long gpa, struct kvm *kvm) { struct page *dpage = NULL; unsigned long bit, uvmem_pfn; struct kvmppc_uvmem_page_pvt *pvt; unsigned long pfn_last, pfn_first; pfn_first = kvmppc_uvmem_pgmap.res.start >> PAGE_SHIFT; pfn_last = pfn_first + (resource_size(&kvmppc_uvmem_pgmap.res) >> PAGE_SHIFT); spin_lock(&kvmppc_uvmem_bitmap_lock); bit = find_first_zero_bit(kvmppc_uvmem_bitmap, pfn_last - pfn_first); if (bit >= (pfn_last - pfn_first)) goto out; bitmap_set(kvmppc_uvmem_bitmap, bit, 1); spin_unlock(&kvmppc_uvmem_bitmap_lock); pvt = kzalloc(sizeof(*pvt), GFP_KERNEL); if (!pvt) goto out_clear; uvmem_pfn = bit + pfn_first; kvmppc_uvmem_pfn_insert(gpa >> PAGE_SHIFT, uvmem_pfn, kvm); pvt->gpa = gpa; pvt->kvm = kvm; dpage = pfn_to_page(uvmem_pfn); dpage->zone_device_data = pvt; get_page(dpage); lock_page(dpage); return dpage; out_clear: spin_lock(&kvmppc_uvmem_bitmap_lock); bitmap_clear(kvmppc_uvmem_bitmap, bit, 1); out: spin_unlock(&kvmppc_uvmem_bitmap_lock); return NULL; } /* * Alloc a PFN from private device memory pool and copy page from normal * memory to secure memory using UV_PAGE_IN uvcall. */ static int kvmppc_svm_page_in(struct vm_area_struct *vma, unsigned long start, unsigned long end, unsigned long gpa, struct kvm *kvm, unsigned long page_shift, bool *downgrade) { unsigned long src_pfn, dst_pfn = 0; struct migrate_vma mig; struct page *spage; unsigned long pfn; struct page *dpage; int ret = 0; memset(&mig, 0, sizeof(mig)); mig.vma = vma; mig.start = start; mig.end = end; mig.src = &src_pfn; mig.dst = &dst_pfn; /* * We come here with mmap_sem write lock held just for * ksm_madvise(), otherwise we only need read mmap_sem. * Hence downgrade to read lock once ksm_madvise() is done. */ ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, MADV_UNMERGEABLE, &vma->vm_flags); downgrade_write(&kvm->mm->mmap_sem); *downgrade = true; if (ret) return ret; ret = migrate_vma_setup(&mig); if (ret) return ret; if (!(*mig.src & MIGRATE_PFN_MIGRATE)) { ret = -1; goto out_finalize; } dpage = kvmppc_uvmem_get_page(gpa, kvm); if (!dpage) { ret = -1; goto out_finalize; } pfn = *mig.src >> MIGRATE_PFN_SHIFT; spage = migrate_pfn_to_page(*mig.src); if (spage) uv_page_in(kvm->arch.lpid, pfn << page_shift, gpa, 0, page_shift); *mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED; migrate_vma_pages(&mig); out_finalize: migrate_vma_finalize(&mig); return ret; } /* * Shares the page with HV, thus making it a normal page. * * - If the page is already secure, then provision a new page and share * - If the page is a normal page, share the existing page * * In the former case, uses dev_pagemap_ops.migrate_to_ram handler * to unmap the device page from QEMU's page tables. */ static unsigned long kvmppc_share_page(struct kvm *kvm, unsigned long gpa, unsigned long page_shift) { int ret = H_PARAMETER; struct page *uvmem_page; struct kvmppc_uvmem_page_pvt *pvt; unsigned long pfn; unsigned long gfn = gpa >> page_shift; int srcu_idx; unsigned long uvmem_pfn; srcu_idx = srcu_read_lock(&kvm->srcu); mutex_lock(&kvm->arch.uvmem_lock); if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, &uvmem_pfn)) { uvmem_page = pfn_to_page(uvmem_pfn); pvt = uvmem_page->zone_device_data; pvt->skip_page_out = true; } retry: mutex_unlock(&kvm->arch.uvmem_lock); pfn = gfn_to_pfn(kvm, gfn); if (is_error_noslot_pfn(pfn)) goto out; mutex_lock(&kvm->arch.uvmem_lock); if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, &uvmem_pfn)) { uvmem_page = pfn_to_page(uvmem_pfn); pvt = uvmem_page->zone_device_data; pvt->skip_page_out = true; kvm_release_pfn_clean(pfn); goto retry; } if (!uv_page_in(kvm->arch.lpid, pfn << page_shift, gpa, 0, page_shift)) ret = H_SUCCESS; kvm_release_pfn_clean(pfn); mutex_unlock(&kvm->arch.uvmem_lock); out: srcu_read_unlock(&kvm->srcu, srcu_idx); return ret; } /* * H_SVM_PAGE_IN: Move page from normal memory to secure memory. * * H_PAGE_IN_SHARED flag makes the page shared which means that the same * memory in is visible from both UV and HV. */ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa, unsigned long flags, unsigned long page_shift) { bool downgrade = false; unsigned long start, end; struct vm_area_struct *vma; int srcu_idx; unsigned long gfn = gpa >> page_shift; int ret; if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START)) return H_UNSUPPORTED; if (page_shift != PAGE_SHIFT) return H_P3; if (flags & ~H_PAGE_IN_SHARED) return H_P2; if (flags & H_PAGE_IN_SHARED) return kvmppc_share_page(kvm, gpa, page_shift); ret = H_PARAMETER; srcu_idx = srcu_read_lock(&kvm->srcu); down_write(&kvm->mm->mmap_sem); start = gfn_to_hva(kvm, gfn); if (kvm_is_error_hva(start)) goto out; mutex_lock(&kvm->arch.uvmem_lock); /* Fail the page-in request of an already paged-in page */ if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL)) goto out_unlock; end = start + (1UL << page_shift); vma = find_vma_intersection(kvm->mm, start, end); if (!vma || vma->vm_start > start || vma->vm_end < end) goto out_unlock; if (!kvmppc_svm_page_in(vma, start, end, gpa, kvm, page_shift, &downgrade)) ret = H_SUCCESS; out_unlock: mutex_unlock(&kvm->arch.uvmem_lock); out: if (downgrade) up_read(&kvm->mm->mmap_sem); else up_write(&kvm->mm->mmap_sem); srcu_read_unlock(&kvm->srcu, srcu_idx); return ret; } /* * Provision a new page on HV side and copy over the contents * from secure memory using UV_PAGE_OUT uvcall. */ static int kvmppc_svm_page_out(struct vm_area_struct *vma, unsigned long start, unsigned long end, unsigned long page_shift, struct kvm *kvm, unsigned long gpa) { unsigned long src_pfn, dst_pfn = 0; struct migrate_vma mig; struct page *dpage, *spage; struct kvmppc_uvmem_page_pvt *pvt; unsigned long pfn; int ret = U_SUCCESS; memset(&mig, 0, sizeof(mig)); mig.vma = vma; mig.start = start; mig.end = end; mig.src = &src_pfn; mig.dst = &dst_pfn; mutex_lock(&kvm->arch.uvmem_lock); /* The requested page is already paged-out, nothing to do */ if (!kvmppc_gfn_is_uvmem_pfn(gpa >> page_shift, kvm, NULL)) goto out; ret = migrate_vma_setup(&mig); if (ret) return ret; spage = migrate_pfn_to_page(*mig.src); if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE)) goto out_finalize; if (!is_zone_device_page(spage)) goto out_finalize; dpage = alloc_page_vma(GFP_HIGHUSER, vma, start); if (!dpage) { ret = -1; goto out_finalize; } lock_page(dpage); pvt = spage->zone_device_data; pfn = page_to_pfn(dpage); /* * This function is used in two cases: * - When HV touches a secure page, for which we do UV_PAGE_OUT * - When a secure page is converted to shared page, we *get* * the page to essentially unmap the device page. In this * case we skip page-out. */ if (!pvt->skip_page_out) ret = uv_page_out(kvm->arch.lpid, pfn << page_shift, gpa, 0, page_shift); if (ret == U_SUCCESS) *mig.dst = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED; else { unlock_page(dpage); __free_page(dpage); goto out_finalize; } migrate_vma_pages(&mig); out_finalize: migrate_vma_finalize(&mig); out: mutex_unlock(&kvm->arch.uvmem_lock); return ret; } /* * Fault handler callback that gets called when HV touches any page that * has been moved to secure memory, we ask UV to give back the page by * issuing UV_PAGE_OUT uvcall. * * This eventually results in dropping of device PFN and the newly * provisioned page/PFN gets populated in QEMU page tables. */ static vm_fault_t kvmppc_uvmem_migrate_to_ram(struct vm_fault *vmf) { struct kvmppc_uvmem_page_pvt *pvt = vmf->page->zone_device_data; if (kvmppc_svm_page_out(vmf->vma, vmf->address, vmf->address + PAGE_SIZE, PAGE_SHIFT, pvt->kvm, pvt->gpa)) return VM_FAULT_SIGBUS; else return 0; } /* * Release the device PFN back to the pool * * Gets called when secure page becomes a normal page during H_SVM_PAGE_OUT. * Gets called with kvm->arch.uvmem_lock held. */ static void kvmppc_uvmem_page_free(struct page *page) { unsigned long pfn = page_to_pfn(page) - (kvmppc_uvmem_pgmap.res.start >> PAGE_SHIFT); struct kvmppc_uvmem_page_pvt *pvt; spin_lock(&kvmppc_uvmem_bitmap_lock); bitmap_clear(kvmppc_uvmem_bitmap, pfn, 1); spin_unlock(&kvmppc_uvmem_bitmap_lock); pvt = page->zone_device_data; page->zone_device_data = NULL; kvmppc_uvmem_pfn_remove(pvt->gpa >> PAGE_SHIFT, pvt->kvm); kfree(pvt); } static const struct dev_pagemap_ops kvmppc_uvmem_ops = { .page_free = kvmppc_uvmem_page_free, .migrate_to_ram = kvmppc_uvmem_migrate_to_ram, }; /* * H_SVM_PAGE_OUT: Move page from secure memory to normal memory. */ unsigned long kvmppc_h_svm_page_out(struct kvm *kvm, unsigned long gpa, unsigned long flags, unsigned long page_shift) { unsigned long gfn = gpa >> page_shift; unsigned long start, end; struct vm_area_struct *vma; int srcu_idx; int ret; if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START)) return H_UNSUPPORTED; if (page_shift != PAGE_SHIFT) return H_P3; if (flags) return H_P2; ret = H_PARAMETER; srcu_idx = srcu_read_lock(&kvm->srcu); down_read(&kvm->mm->mmap_sem); start = gfn_to_hva(kvm, gfn); if (kvm_is_error_hva(start)) goto out; end = start + (1UL << page_shift); vma = find_vma_intersection(kvm->mm, start, end); if (!vma || vma->vm_start > start || vma->vm_end < end) goto out; if (!kvmppc_svm_page_out(vma, start, end, page_shift, kvm, gpa)) ret = H_SUCCESS; out: up_read(&kvm->mm->mmap_sem); srcu_read_unlock(&kvm->srcu, srcu_idx); return ret; } static u64 kvmppc_get_secmem_size(void) { struct device_node *np; int i, len; const __be32 *prop; u64 size = 0; np = of_find_compatible_node(NULL, NULL, "ibm,uv-firmware"); if (!np) goto out; prop = of_get_property(np, "secure-memory-ranges", &len); if (!prop) goto out_put; for (i = 0; i < len / (sizeof(*prop) * 4); i++) size += of_read_number(prop + (i * 4) + 2, 2); out_put: of_node_put(np); out: return size; } int kvmppc_uvmem_init(void) { int ret = 0; unsigned long size; struct resource *res; void *addr; unsigned long pfn_last, pfn_first; size = kvmppc_get_secmem_size(); if (!size) { /* * Don't fail the initialization of kvm-hv module if * the platform doesn't export ibm,uv-firmware node. * Let normal guests run on such PEF-disabled platform. */ pr_info("KVMPPC-UVMEM: No support for secure guests\n"); goto out; } res = request_free_mem_region(&iomem_resource, size, "kvmppc_uvmem"); if (IS_ERR(res)) { ret = PTR_ERR(res); goto out; } kvmppc_uvmem_pgmap.type = MEMORY_DEVICE_PRIVATE; kvmppc_uvmem_pgmap.res = *res; kvmppc_uvmem_pgmap.ops = &kvmppc_uvmem_ops; addr = memremap_pages(&kvmppc_uvmem_pgmap, NUMA_NO_NODE); if (IS_ERR(addr)) { ret = PTR_ERR(addr); goto out_free_region; } pfn_first = res->start >> PAGE_SHIFT; pfn_last = pfn_first + (resource_size(res) >> PAGE_SHIFT); kvmppc_uvmem_bitmap = kcalloc(BITS_TO_LONGS(pfn_last - pfn_first), sizeof(unsigned long), GFP_KERNEL); if (!kvmppc_uvmem_bitmap) { ret = -ENOMEM; goto out_unmap; } pr_info("KVMPPC-UVMEM: Secure Memory size 0x%lx\n", size); return ret; out_unmap: memunmap_pages(&kvmppc_uvmem_pgmap); out_free_region: release_mem_region(res->start, size); out: return ret; } void kvmppc_uvmem_free(void) { memunmap_pages(&kvmppc_uvmem_pgmap); release_mem_region(kvmppc_uvmem_pgmap.res.start, resource_size(&kvmppc_uvmem_pgmap.res)); kfree(kvmppc_uvmem_bitmap); }