3 files changed, 62 insertions, 45 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 152312c1fafa..7facebd1911d 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -252,6 +252,7 @@ struct kvm_stat {
         u32 halt_exits;
         u32 request_irq_exits;
         u32 irq_exits;
+        u32 light_exits;
 };
 
 struct kvm_vcpu {
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 8f1f07adb04e..7d682586423b 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -72,6 +72,7 @@ static struct kvm_stats_debugfs_item {
         { "halt_exits", STAT_OFFSET(halt_exits) },
         { "request_irq", STAT_OFFSET(request_irq_exits) },
         { "irq_exits", STAT_OFFSET(irq_exits) },
+        { "light_exits", STAT_OFFSET(light_exits) },
         { NULL }
 };
 
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index 52bd5f079df1..84ce0c0930a0 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -483,6 +483,13 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
         case MSR_GS_BASE:
                 vmcs_writel(GUEST_GS_BASE, data);
                 break;
+        case MSR_LSTAR:
+        case MSR_SYSCALL_MASK:
+                msr = find_msr_entry(vcpu, msr_index);
+                if (msr)
+                        msr->data = data;
+                load_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
+                break;
 #endif
         case MSR_IA32_SYSENTER_CS:
                 vmcs_write32(GUEST_SYSENTER_CS, data);
@@ -1820,7 +1827,7 @@ static int vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         int fs_gs_ldt_reload_needed;
         int r;
 
-again:
+preempted:
         /*
          * Set host fs and gs selectors.  Unfortunately, 22.2.3 does not
          * allow segment selectors with cpl > 0 or ti == 1.
@@ -1851,13 +1858,6 @@ again:
         if (vcpu->guest_debug.enabled)
                 kvm_guest_debug_pre(vcpu);
 
-        kvm_load_guest_fpu(vcpu);
-
-        /*
-         * Loading guest fpu may have cleared host cr0.ts
-         */
-        vmcs_writel(HOST_CR0, read_cr0());
-
 #ifdef CONFIG_X86_64
         if (is_long_mode(vcpu)) {
                 save_msrs(vcpu->host_msrs + msr_offset_kernel_gs_base, 1);
@@ -1865,6 +1865,14 @@ again:
         }
 #endif
 
+again:
+        kvm_load_guest_fpu(vcpu);
+
+        /*
+         * Loading guest fpu may have cleared host cr0.ts
+         */
+        vmcs_writel(HOST_CR0, read_cr0());
+
         asm (
                 /* Store host registers */
                 "pushf \n\t"
@@ -1984,36 +1992,8 @@ again:
                 [cr2]"i"(offsetof(struct kvm_vcpu, cr2))
               : "cc", "memory" );
 
-        /*
-         * Reload segment selectors ASAP. (it's needed for a functional
-         * kernel: x86 relies on having __KERNEL_PDA in %fs and x86_64
-         * relies on having 0 in %gs for the CPU PDA to work.)
-         */
-        if (fs_gs_ldt_reload_needed) {
-                load_ldt(ldt_sel);
-                load_fs(fs_sel);
-                /*
-                 * If we have to reload gs, we must take care to
-                 * preserve our gs base.
-                 */
-                local_irq_disable();
-                load_gs(gs_sel);
-#ifdef CONFIG_X86_64
-                wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
-#endif
-                local_irq_enable();
-
-                reload_tss();
-        }
         ++vcpu->stat.exits;
 
-#ifdef CONFIG_X86_64
-        if (is_long_mode(vcpu)) {
-                save_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
-                load_msrs(vcpu->host_msrs, NR_BAD_MSRS);
-        }
-#endif
-
         vcpu->interrupt_window_open = (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0;
 
         asm ("mov %0, %%ds; mov %0, %%es" : : "r"(__USER_DS));
@@ -2035,24 +2015,59 @@ again:
                 if (r > 0) {
                         /* Give scheduler a change to reschedule. */
                         if (signal_pending(current)) {
-                                ++vcpu->stat.signal_exits;
-                                post_kvm_run_save(vcpu, kvm_run);
+                                r = -EINTR;
                                 kvm_run->exit_reason = KVM_EXIT_INTR;
-                                return -EINTR;
+                                ++vcpu->stat.signal_exits;
+                                goto out;
                         }
 
                         if (dm_request_for_irq_injection(vcpu, kvm_run)) {
-                                ++vcpu->stat.request_irq_exits;
-                                post_kvm_run_save(vcpu, kvm_run);
+                                r = -EINTR;
                                 kvm_run->exit_reason = KVM_EXIT_INTR;
-                                return -EINTR;
+                                ++vcpu->stat.request_irq_exits;
+                                goto out;
+                        }
+                        if (!need_resched()) {
+                                ++vcpu->stat.light_exits;
+                                goto again;
                         }
-
-                        kvm_resched(vcpu);
-                        goto again;
                 }
         }
 
+out:
+        /*
+         * Reload segment selectors ASAP. (it's needed for a functional
+         * kernel: x86 relies on having __KERNEL_PDA in %fs and x86_64
+         * relies on having 0 in %gs for the CPU PDA to work.)
+         */
+        if (fs_gs_ldt_reload_needed) {
+                load_ldt(ldt_sel);
+                load_fs(fs_sel);
+                /*
+                 * If we have to reload gs, we must take care to
+                 * preserve our gs base.
+                 */
+                local_irq_disable();
+                load_gs(gs_sel);
+#ifdef CONFIG_X86_64
+                wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
+#endif
+                local_irq_enable();
+
+                reload_tss();
+        }
+#ifdef CONFIG_X86_64
+        if (is_long_mode(vcpu)) {
+                save_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
+                load_msrs(vcpu->host_msrs, NR_BAD_MSRS);
+        }
+#endif
+
+        if (r > 0) {
+                kvm_resched(vcpu);
+                goto preempted;
+        }
+
         post_kvm_run_save(vcpu, kvm_run);
         return r;
 }