Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/avi/kvm

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/avi/kvm:
  KVM: disable writeback for 0x0f 0x01 instructions.
  KVM: Fix removal of nx capability from guest cpuid
  Revert "KVM: Avoid useless memory write when possible"
  KVM: Fix unlikely kvm_create vs decache_vcpus_on_cpu race
  KVM: Correctly handle writes crossing a page boundary

2 files changed, 33 insertions, 13 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index bcbe6835beb4..96856097d15b 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -297,9 +297,6 @@ static struct kvm *kvm_create_vm(void)
         kvm_io_bus_init(&kvm->pio_bus);
         spin_lock_init(&kvm->lock);
         INIT_LIST_HEAD(&kvm->active_mmu_pages);
-        spin_lock(&kvm_lock);
-        list_add(&kvm->vm_list, &vm_list);
-        spin_unlock(&kvm_lock);
         kvm_io_bus_init(&kvm->mmio_bus);
         for (i = 0; i < KVM_MAX_VCPUS; ++i) {
                 struct kvm_vcpu *vcpu = &kvm->vcpus[i];
@@ -309,6 +306,9 @@ static struct kvm *kvm_create_vm(void)
                 vcpu->kvm = kvm;
                 vcpu->mmu.root_hpa = INVALID_PAGE;
         }
+        spin_lock(&kvm_lock);
+        list_add(&kvm->vm_list, &vm_list);
+        spin_unlock(&kvm_lock);
         return kvm;
 }
 
@@ -1070,18 +1070,16 @@ static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
                 return 0;
         mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT);
         virt = kmap_atomic(page, KM_USER0);
-        if (memcmp(virt + offset_in_page(gpa), val, bytes)) {
-                kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes);
-                memcpy(virt + offset_in_page(gpa), val, bytes);
-        }
+        kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes);
+        memcpy(virt + offset_in_page(gpa), val, bytes);
         kunmap_atomic(virt, KM_USER0);
         return 1;
 }
 
-static int emulator_write_emulated(unsigned long addr,
-                                   const void *val,
-                                   unsigned int bytes,
-                                   struct x86_emulate_ctxt *ctxt)
+static int emulator_write_emulated_onepage(unsigned long addr,
+                                           const void *val,
+                                           unsigned int bytes,
+                                           struct x86_emulate_ctxt *ctxt)
 {
         struct kvm_vcpu      *vcpu = ctxt->vcpu;
         struct kvm_io_device *mmio_dev;
@@ -1113,6 +1111,26 @@ static int emulator_write_emulated(unsigned long addr,
         return X86EMUL_CONTINUE;
 }
 
+static int emulator_write_emulated(unsigned long addr,
+                                   const void *val,
+                                   unsigned int bytes,
+                                   struct x86_emulate_ctxt *ctxt)
+{
+        /* Crossing a page boundary? */
+        if (((addr + bytes - 1) ^ addr) & PAGE_MASK) {
+                int rc, now;
+
+                now = -addr & ~PAGE_MASK;
+                rc = emulator_write_emulated_onepage(addr, val, now, ctxt);
+                if (rc != X86EMUL_CONTINUE)
+                        return rc;
+                addr += now;
+                val += now;
+                bytes -= now;
+        }
+        return emulator_write_emulated_onepage(addr, val, bytes, ctxt);
+}
+
 static int emulator_cmpxchg_emulated(unsigned long addr,
                                      const void *old,
                                      const void *new,
@@ -2414,9 +2432,9 @@ static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu)
                         break;
                 }
         }
-        if (entry && (entry->edx & EFER_NX) && !(efer & EFER_NX)) {
+        if (entry && (entry->edx & (1 << 20)) && !(efer & EFER_NX)) {
                 entry->edx &= ~(1 << 20);
-                printk(KERN_INFO ": guest NX capability removed\n");
+                printk(KERN_INFO "kvm: guest NX capability removed\n");
         }
 }
 
diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 1b800fc00342..1f979cb0df31 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1178,6 +1178,8 @@ pop_instruction:
 twobyte_insn:
         switch (b) {
         case 0x01: /* lgdt, lidt, lmsw */
+                /* Disable writeback. */
+                no_wb = 1;
                 switch (modrm_reg) {
                         u16 size;
                         unsigned long address;