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Shutemov" X-Google-Original-From: "Kirill A. Shutemov" Received: by box.localdomain (Postfix, from userid 1000) id 24A6D102F6C; Tue, 20 Oct 2020 09:19:02 +0300 (+03) To: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Cc: David Rientjes , Andrea Arcangeli , Kees Cook , Will Drewry , "Edgecombe, Rick P" , "Kleen, Andi" , Liran Alon , Mike Rapoport , x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [RFCv2 13/16] KVM: Rework copy_to/from_guest() to avoid direct mapping Date: Tue, 20 Oct 2020 09:18:56 +0300 Message-Id: <20201020061859.18385-14-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201020061859.18385-1-kirill.shutemov@linux.intel.com> References: <20201020061859.18385-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We are going unmap guest pages from direct mapping and cannot rely on it for guest memory access. Use temporary kmap_atomic()-style mapping to access guest memory. Signed-off-by: Kirill A. Shutemov --- virt/kvm/kvm_main.c | 27 ++++++++++- virt/lib/mem_protected.c | 101 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 126 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 4c008c7b4974..9b569b78874a 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -51,6 +51,7 @@ #include #include #include +#include #include #include @@ -154,6 +155,12 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm); static unsigned long long kvm_createvm_count; static unsigned long long kvm_active_vms; +void *kvm_map_page_atomic(struct page *page); +void kvm_unmap_page_atomic(void *vaddr); + +int kvm_init_protected_memory(void); +void kvm_exit_protected_memory(void); + int __kvm_protect_memory(unsigned long start, unsigned long end, bool protect); __weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm, @@ -2329,6 +2336,7 @@ int copy_from_guest(void *data, unsigned long hva, int len, bool protected) int offset = offset_in_page(hva); struct page *page; int npages, seg; + void *vaddr; if (!protected) return __copy_from_user(data, (void __user *)hva, len); @@ -2341,7 +2349,11 @@ int copy_from_guest(void *data, unsigned long hva, int len, bool protected) npages = get_user_pages_unlocked(hva, 1, &page, FOLL_KVM); if (npages != 1) return -EFAULT; - memcpy(data, page_address(page) + offset, seg); + + vaddr = kvm_map_page_atomic(page); + memcpy(data, vaddr + offset, seg); + kvm_unmap_page_atomic(vaddr); + put_page(page); len -= seg; hva += seg; @@ -2356,6 +2368,7 @@ int copy_to_guest(unsigned long hva, const void *data, int len, bool protected) int offset = offset_in_page(hva); struct page *page; int npages, seg; + void *vaddr; if (!protected) return __copy_to_user((void __user *)hva, data, len); @@ -2369,7 +2382,11 @@ int copy_to_guest(unsigned long hva, const void *data, int len, bool protected) FOLL_WRITE | FOLL_KVM); if (npages != 1) return -EFAULT; - memcpy(page_address(page) + offset, data, seg); + + vaddr = kvm_map_page_atomic(page); + memcpy(vaddr + offset, data, seg); + kvm_unmap_page_atomic(vaddr); + put_page(page); len -= seg; hva += seg; @@ -4945,6 +4962,10 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, if (r) goto out_free; + if (IS_ENABLED(CONFIG_HAVE_KVM_PROTECTED_MEMORY) && + kvm_init_protected_memory()) + goto out_unreg; + kvm_chardev_ops.owner = module; kvm_vm_fops.owner = module; kvm_vcpu_fops.owner = module; @@ -4968,6 +4989,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, return 0; out_unreg: + kvm_exit_protected_memory(); kvm_async_pf_deinit(); out_free: kmem_cache_destroy(kvm_vcpu_cache); @@ -4989,6 +5011,7 @@ EXPORT_SYMBOL_GPL(kvm_init); void kvm_exit(void) { + kvm_exit_protected_memory(); debugfs_remove_recursive(kvm_debugfs_dir); misc_deregister(&kvm_dev); kmem_cache_destroy(kvm_vcpu_cache); diff --git a/virt/lib/mem_protected.c b/virt/lib/mem_protected.c index 0b01dd74f29c..1dfe82534242 100644 --- a/virt/lib/mem_protected.c +++ b/virt/lib/mem_protected.c @@ -5,6 +5,100 @@ #include #include +static pte_t **guest_map_ptes; +static struct vm_struct *guest_map_area; + +void *kvm_map_page_atomic(struct page *page) +{ + pte_t *pte; + void *vaddr; + + preempt_disable(); + pte = guest_map_ptes[smp_processor_id()]; + vaddr = guest_map_area->addr + smp_processor_id() * PAGE_SIZE; + set_pte(pte, mk_pte(page, PAGE_KERNEL)); + return vaddr; +} +EXPORT_SYMBOL_GPL(kvm_map_page_atomic); + +void kvm_unmap_page_atomic(void *vaddr) +{ + pte_t *pte = guest_map_ptes[smp_processor_id()]; + set_pte(pte, __pte(0)); + flush_tlb_one_kernel((unsigned long)vaddr); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(kvm_unmap_page_atomic); + +int kvm_init_protected_memory(void) +{ + guest_map_ptes = kmalloc_array(num_possible_cpus(), + sizeof(pte_t *), GFP_KERNEL); + if (!guest_map_ptes) + return -ENOMEM; + + guest_map_area = alloc_vm_area(PAGE_SIZE * num_possible_cpus(), + guest_map_ptes); + if (!guest_map_ptes) { + kfree(guest_map_ptes); + return -ENOMEM; + } + + return 0; +} +EXPORT_SYMBOL_GPL(kvm_init_protected_memory); + +void kvm_exit_protected_memory(void) +{ + if (guest_map_area) + free_vm_area(guest_map_area); + if (guest_map_ptes) + kfree(guest_map_ptes); +} +EXPORT_SYMBOL_GPL(kvm_exit_protected_memory); + +static int adjust_direct_mapping_pte_range(pmd_t *pmd, unsigned long addr, + unsigned long end, + struct mm_walk *walk) +{ + bool protect = (bool)walk->private; + pte_t *pte; + struct page *page; + + if (pmd_trans_huge(*pmd)) { + page = pmd_page(*pmd); + if (is_huge_zero_page(page)) + return 0; + VM_BUG_ON_PAGE(total_mapcount(page) != 1, page); + /* XXX: Would it fail with direct device assignment? */ + VM_BUG_ON_PAGE(page_count(page) != 1, page); + kernel_map_pages(page, HPAGE_PMD_NR, !protect); + return 0; + } + + pte = pte_offset_map(pmd, addr); + for (; addr != end; pte++, addr += PAGE_SIZE) { + pte_t entry = *pte; + + if (!pte_present(entry)) + continue; + + if (is_zero_pfn(pte_pfn(entry))) + continue; + + page = pte_page(entry); + + VM_BUG_ON_PAGE(page_mapcount(page) != 1, page); + kernel_map_pages(page, 1, !protect); + } + + return 0; +} + +static const struct mm_walk_ops adjust_direct_mapping_ops = { + .pmd_entry = adjust_direct_mapping_pte_range, +}; + int __kvm_protect_memory(unsigned long start, unsigned long end, bool protect) { struct mm_struct *mm = current->mm; @@ -50,6 +144,13 @@ int __kvm_protect_memory(unsigned long start, unsigned long end, bool protect) if (ret) goto out; + if (vma_is_anonymous(vma)) { + ret = walk_page_range_novma(mm, start, tmp, + &adjust_direct_mapping_ops, NULL, + (void *) protect); + if (ret) + goto out; + } next: start = tmp; if (start < prev->vm_end) -- 2.26.2