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Date: Tue, 20 Oct 2020 09:18:56 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>
Cc: David Rientjes <rientjes@...gle.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Kees Cook <keescook@...omium.org>,
Will Drewry <wad@...omium.org>,
"Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
"Kleen, Andi" <andi.kleen@...el.com>,
Liran Alon <liran.alon@...cle.com>,
Mike Rapoport <rppt@...nel.org>, x86@...nel.org,
kvm@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [RFCv2 13/16] KVM: Rework copy_to/from_guest() to avoid direct mapping
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 <kirill.shutemov@...ux.intel.com>
---
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 <linux/io.h>
#include <linux/lockdep.h>
#include <linux/kthread.h>
+#include <linux/pagewalk.h>
#include <asm/processor.h>
#include <asm/ioctl.h>
@@ -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 <linux/vmalloc.h>
#include <asm/tlbflush.h>
+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
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