7 files changed, 102 insertions, 28 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index bf33aaa4c59f..b91bfd43f007 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -857,7 +857,8 @@ struct kvm_userspace_memory_region {
 };
 
 /* for kvm_memory_region::flags */
-#define KVM_MEM_LOG_DIRTY_PAGES  1UL
+#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
+#define KVM_MEM_READONLY        (1UL << 1)
 
 This ioctl allows the user to create or modify a guest physical memory
 slot.  When changing an existing slot, it may be moved in the guest
@@ -873,9 +874,12 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
 be identical.  This allows large pages in the guest to be backed by large
 pages in the host.
 
-The flags field supports just one flag, KVM_MEM_LOG_DIRTY_PAGES, which
+The flags field supports two flag, KVM_MEM_LOG_DIRTY_PAGES, which
 instructs kvm to keep track of writes to memory within the slot.  See
-the KVM_GET_DIRTY_LOG ioctl.
+the KVM_GET_DIRTY_LOG ioctl. Another flag is KVM_MEM_READONLY when the
+KVM_CAP_READONLY_MEM capability, it indicates the guest memory is read-only,
+that means, guest is only allowed to read it. Writes will be posted to
+userspace as KVM_EXIT_MMIO exits.
 
 When the KVM_CAP_SYNC_MMU capability, changes in the backing of the memory
 region are automatically reflected into the guest.  For example, an mmap()
diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
index 246617efd67f..521bf252e34b 100644
--- a/arch/x86/include/asm/kvm.h
+++ b/arch/x86/include/asm/kvm.h
@@ -25,6 +25,7 @@
 #define __KVM_HAVE_DEBUGREGS
 #define __KVM_HAVE_XSAVE
 #define __KVM_HAVE_XCRS
+#define __KVM_HAVE_READONLY_MEM
 
 /* Architectural interrupt line count. */
 #define KVM_NR_INTERRUPTS 256
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5548971ae80d..8e312a2e1412 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2647,6 +2647,15 @@ static void kvm_send_hwpoison_signal(unsigned long address, struct task_struct *
 
 static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, pfn_t pfn)
 {
+        /*
+         * Do not cache the mmio info caused by writing the readonly gfn
+         * into the spte otherwise read access on readonly gfn also can
+         * caused mmio page fault and treat it as mmio access.
+         * Return 1 to tell kvm to emulate it.
+         */
+        if (pfn == KVM_PFN_ERR_RO_FAULT)
+                return 1;
+
         if (pfn == KVM_PFN_ERR_HWPOISON) {
                 kvm_send_hwpoison_signal(gfn_to_hva(vcpu->kvm, gfn), current);
                 return 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 704680d0fa3e..42bbf4187d20 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2175,6 +2175,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_GET_TSC_KHZ:
         case KVM_CAP_PCI_2_3:
         case KVM_CAP_KVMCLOCK_CTRL:
+        case KVM_CAP_READONLY_MEM:
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO:
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 2de335d7f63e..d808694673f9 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -106,7 +106,8 @@ struct kvm_userspace_memory_region {
  * other bits are reserved for kvm internal use which are defined in
  * include/linux/kvm_host.h.
  */
-#define KVM_MEM_LOG_DIRTY_PAGES  1UL
+#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
+#define KVM_MEM_READONLY        (1UL << 1)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
@@ -621,6 +622,9 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_PPC_GET_SMMU_INFO 78
 #define KVM_CAP_S390_COW 79
 #define KVM_CAP_PPC_ALLOC_HTAB 80
+#ifdef __KVM_HAVE_READONLY_MEM
+#define KVM_CAP_READONLY_MEM 81
+#endif
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a913ac709a9d..5972c9845ddb 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -465,6 +465,7 @@ int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
 
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
+unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn);
 void kvm_release_page_clean(struct page *page);
 void kvm_release_page_dirty(struct page *page);
 void kvm_set_page_dirty(struct page *page);
@@ -792,12 +793,6 @@ hva_to_gfn_memslot(unsigned long hva, struct kvm_memory_slot *slot)
         return slot->base_gfn + gfn_offset;
 }
 
-static inline unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
-                                               gfn_t gfn)
-{
-        return slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE;
-}
-
 static inline gpa_t gfn_to_gpa(gfn_t gfn)
 {
         return (gpa_t)gfn << PAGE_SHIFT;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e3e1658c491d..3416f8a31f63 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -680,7 +680,13 @@ void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)
 
 static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
 {
-        if (mem->flags & ~KVM_MEM_LOG_DIRTY_PAGES)
+        u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
+
+#ifdef KVM_CAP_READONLY_MEM
+        valid_flags |= KVM_MEM_READONLY;
+#endif
+
+        if (mem->flags & ~valid_flags)
                 return -EINVAL;
 
         return 0;
@@ -973,18 +979,45 @@ out:
         return size;
 }
 
-static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
-                                     gfn_t *nr_pages)
+static bool memslot_is_readonly(struct kvm_memory_slot *slot)
+{
+        return slot->flags & KVM_MEM_READONLY;
+}
+
+static unsigned long __gfn_to_hva_memslot(struct kvm_memory_slot *slot,
+                                          gfn_t gfn)
+{
+        return slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE;
+}
+
+static unsigned long __gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
+                                       gfn_t *nr_pages, bool write)
 {
         if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                 return KVM_HVA_ERR_BAD;
 
+        if (memslot_is_readonly(slot) && write)
+                return KVM_HVA_ERR_RO_BAD;
+
         if (nr_pages)
                 *nr_pages = slot->npages - (gfn - slot->base_gfn);
 
-        return gfn_to_hva_memslot(slot, gfn);
+        return __gfn_to_hva_memslot(slot, gfn);
 }
 
+static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
+                                     gfn_t *nr_pages)
+{
+        return __gfn_to_hva_many(slot, gfn, nr_pages, true);
+}
+
+unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
+                                 gfn_t gfn)
+{
+        return gfn_to_hva_many(slot, gfn, NULL);
+}
+EXPORT_SYMBOL_GPL(gfn_to_hva_memslot);
+
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 {
         return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
@@ -997,7 +1030,7 @@ EXPORT_SYMBOL_GPL(gfn_to_hva);
  */
 static unsigned long gfn_to_hva_read(struct kvm *kvm, gfn_t gfn)
 {
-        return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
+        return __gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL, false);
 }
 
 static int kvm_read_hva(void *data, void __user *hva, int len)
@@ -1106,6 +1139,17 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
         return npages;
 }
 
+static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
+{
+        if (unlikely(!(vma->vm_flags & VM_READ)))
+                return false;
+
+        if (write_fault && (unlikely(!(vma->vm_flags & VM_WRITE))))
+                return false;
+
+        return true;
+}
+
 /*
  * Pin guest page in memory and return its pfn.
  * @addr: host virtual address which maps memory to the guest
@@ -1130,8 +1174,6 @@ static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
         /* we can do it either atomically or asynchronously, not both */
         BUG_ON(atomic && async);
 
-        BUG_ON(!write_fault && !writable);
-
         if (hva_to_pfn_fast(addr, atomic, async, write_fault, writable, &pfn))
                 return pfn;
 
@@ -1158,7 +1200,7 @@ static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
                         vma->vm_pgoff;
                 BUG_ON(!kvm_is_mmio_pfn(pfn));
         } else {
-                if (async && (vma->vm_flags & VM_WRITE))
+                if (async && vma_is_valid(vma, write_fault))
                         *async = true;
                 pfn = KVM_PFN_ERR_FAULT;
         }
@@ -1167,19 +1209,40 @@ exit:
         return pfn;
 }
 
+static pfn_t
+__gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn, bool atomic,
+                     bool *async, bool write_fault, bool *writable)
+{
+        unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);
+
+        if (addr == KVM_HVA_ERR_RO_BAD)
+                return KVM_PFN_ERR_RO_FAULT;
+
+        if (kvm_is_error_hva(addr))
+                return KVM_PFN_ERR_BAD;
+
+        /* Do not map writable pfn in the readonly memslot. */
+        if (writable && memslot_is_readonly(slot)) {
+                *writable = false;
+                writable = NULL;
+        }
+
+        return hva_to_pfn(addr, atomic, async, write_fault,
+                          writable);
+}
+
 static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async,
                           bool write_fault, bool *writable)
 {
-        unsigned long addr;
+        struct kvm_memory_slot *slot;
 
         if (async)
                 *async = false;
 
-        addr = gfn_to_hva(kvm, gfn);
-        if (kvm_is_error_hva(addr))
-                return KVM_PFN_ERR_BAD;
+        slot = gfn_to_memslot(kvm, gfn);
 
-        return hva_to_pfn(addr, atomic, async, write_fault, writable);
+        return __gfn_to_pfn_memslot(slot, gfn, atomic, async, write_fault,
+                                    writable);
 }
 
 pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn)
@@ -1210,15 +1273,12 @@ EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);
 
 pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
 {
-        unsigned long addr = gfn_to_hva_memslot(slot, gfn);
-        return hva_to_pfn(addr, false, NULL, true, NULL);
+        return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL);
 }
 
 pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn)
 {
-        unsigned long addr = gfn_to_hva_memslot(slot, gfn);
-
-        return hva_to_pfn(addr, true, NULL, true, NULL);
+        return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);