KVM: VMX: Use shared msr infrastructure

Instead of reloading syscall MSRs on every preemption, use the new shared
msr infrastructure to reload them at the last possible minute (just before
exit to userspace).

Improves vcpu/idle/vcpu switches by about 2000 cycles (when EFER needs to be
reloaded as well).

[jan: fix slot index missing indirection]

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 42 insertions, 70 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 32512519e1ac..bf46253149c3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -86,6 +86,11 @@ struct vmcs {
         char data[0];
 };
 
+struct shared_msr_entry {
+        unsigned index;
+        u64 data;
+};
+
 struct vcpu_vmx {
         struct kvm_vcpu       vcpu;
         struct list_head      local_vcpus_link;
@@ -93,8 +98,7 @@ struct vcpu_vmx {
         int                   launched;
         u8                    fail;
         u32                   idt_vectoring_info;
-        struct kvm_msr_entry *guest_msrs;
-        struct kvm_msr_entry *host_msrs;
+        struct shared_msr_entry *guest_msrs;
         int                   nmsrs;
         int                   save_nmsrs;
         int                   msr_offset_efer;
@@ -108,7 +112,6 @@ struct vcpu_vmx {
                 u16           fs_sel, gs_sel, ldt_sel;
                 int           gs_ldt_reload_needed;
                 int           fs_reload_needed;
-                int           guest_efer_loaded;
         } host_state;
         struct {
                 int vm86_active;
@@ -195,6 +198,8 @@ static struct kvm_vmx_segment_field {
         VMX_SEGMENT_FIELD(LDTR),
 };
 
+static u64 host_efer;
+
 static void ept_save_pdptrs(struct kvm_vcpu *vcpu);
 
 /*
@@ -209,22 +214,6 @@ static const u32 vmx_msr_index[] = {
 };
 #define NR_VMX_MSR ARRAY_SIZE(vmx_msr_index)
 
-static void load_msrs(struct kvm_msr_entry *e, int n)
-{
-        int i;
-
-        for (i = 0; i < n; ++i)
-                wrmsrl(e[i].index, e[i].data);
-}
-
-static void save_msrs(struct kvm_msr_entry *e, int n)
-{
-        int i;
-
-        for (i = 0; i < n; ++i)
-                rdmsrl(e[i].index, e[i].data);
-}
-
 static inline int is_page_fault(u32 intr_info)
 {
         return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK |
@@ -373,7 +362,7 @@ static int __find_msr_index(struct vcpu_vmx *vmx, u32 msr)
         int i;
 
         for (i = 0; i < vmx->nmsrs; ++i)
-                if (vmx->guest_msrs[i].index == msr)
+                if (vmx_msr_index[vmx->guest_msrs[i].index] == msr)
                         return i;
         return -1;
 }
@@ -404,7 +393,7 @@ static inline void __invept(int ext, u64 eptp, gpa_t gpa)
                         : : "a" (&operand), "c" (ext) : "cc", "memory");
 }
 
-static struct kvm_msr_entry *find_msr_entry(struct vcpu_vmx *vmx, u32 msr)
+static struct shared_msr_entry *find_msr_entry(struct vcpu_vmx *vmx, u32 msr)
 {
         int i;
 
@@ -595,17 +584,15 @@ static void reload_tss(void)
         load_TR_desc();
 }
 
-static void load_transition_efer(struct vcpu_vmx *vmx)
+static bool update_transition_efer(struct vcpu_vmx *vmx)
 {
         int efer_offset = vmx->msr_offset_efer;
-        u64 host_efer;
         u64 guest_efer;
         u64 ignore_bits;
 
         if (efer_offset < 0)
-                return;
-        host_efer = vmx->host_msrs[efer_offset].data;
-        guest_efer = vmx->guest_msrs[efer_offset].data;
+                return false;
+        guest_efer = vmx->vcpu.arch.shadow_efer;
 
         /*
          * NX is emulated; LMA and LME handled by hardware; SCE meaninless
@@ -619,26 +606,18 @@ static void load_transition_efer(struct vcpu_vmx *vmx)
                 ignore_bits &= ~(u64)EFER_SCE;
 #endif
         if ((guest_efer & ~ignore_bits) == (host_efer & ~ignore_bits))
-                return;
+                return false;
 
-        vmx->host_state.guest_efer_loaded = 1;
         guest_efer &= ~ignore_bits;
         guest_efer |= host_efer & ignore_bits;
-        wrmsrl(MSR_EFER, guest_efer);
-        vmx->vcpu.stat.efer_reload++;
-}
-
-static void reload_host_efer(struct vcpu_vmx *vmx)
-{
-        if (vmx->host_state.guest_efer_loaded) {
-                vmx->host_state.guest_efer_loaded = 0;
-                load_msrs(vmx->host_msrs + vmx->msr_offset_efer, 1);
-        }
+        vmx->guest_msrs[efer_offset].data = guest_efer;
+        return true;
 }
 
 static void vmx_save_host_state(struct kvm_vcpu *vcpu)
 {
         struct vcpu_vmx *vmx = to_vmx(vcpu);
+        int i;
 
         if (vmx->host_state.loaded)
                 return;
@@ -680,8 +659,9 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
                 wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
         }
 #endif
-        load_msrs(vmx->guest_msrs, vmx->save_nmsrs);
-        load_transition_efer(vmx);
+        for (i = 0; i < vmx->save_nmsrs; ++i)
+                kvm_set_shared_msr(vmx->guest_msrs[i].index,
+                                   vmx->guest_msrs[i].data);
 }
 
 static void __vmx_load_host_state(struct vcpu_vmx *vmx)
@@ -709,9 +689,6 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
                 local_irq_restore(flags);
         }
         reload_tss();
-        save_msrs(vmx->guest_msrs, vmx->save_nmsrs);
-        load_msrs(vmx->host_msrs, vmx->save_nmsrs);
-        reload_host_efer(vmx);
 #ifdef CONFIG_X86_64
         if (is_long_mode(&vmx->vcpu)) {
                 rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
@@ -908,19 +885,14 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
 /*
  * Swap MSR entry in host/guest MSR entry array.
  */
-#ifdef CONFIG_X86_64
 static void move_msr_up(struct vcpu_vmx *vmx, int from, int to)
 {
-        struct kvm_msr_entry tmp;
+        struct shared_msr_entry tmp;
 
         tmp = vmx->guest_msrs[to];
         vmx->guest_msrs[to] = vmx->guest_msrs[from];
         vmx->guest_msrs[from] = tmp;
-        tmp = vmx->host_msrs[to];
-        vmx->host_msrs[to] = vmx->host_msrs[from];
-        vmx->host_msrs[from] = tmp;
 }
-#endif
 
 /*
  * Set up the vmcs to automatically save and restore system
@@ -929,15 +901,13 @@ static void move_msr_up(struct vcpu_vmx *vmx, int from, int to)
  */
 static void setup_msrs(struct vcpu_vmx *vmx)
 {
-        int save_nmsrs;
+        int save_nmsrs, index;
         unsigned long *msr_bitmap;
 
         vmx_load_host_state(vmx);
         save_nmsrs = 0;
 #ifdef CONFIG_X86_64
         if (is_long_mode(&vmx->vcpu)) {
-                int index;
-
                 index = __find_msr_index(vmx, MSR_SYSCALL_MASK);
                 if (index >= 0)
                         move_msr_up(vmx, index, save_nmsrs++);
@@ -956,9 +926,11 @@ static void setup_msrs(struct vcpu_vmx *vmx)
                         move_msr_up(vmx, index, save_nmsrs++);
         }
 #endif
-        vmx->save_nmsrs = save_nmsrs;
+        vmx->msr_offset_efer = index = __find_msr_index(vmx, MSR_EFER);
+        if (index >= 0 && update_transition_efer(vmx))
+                move_msr_up(vmx, index, save_nmsrs++);
 
-        vmx->msr_offset_efer = __find_msr_index(vmx, MSR_EFER);
+        vmx->save_nmsrs = save_nmsrs;
 
         if (cpu_has_vmx_msr_bitmap()) {
                 if (is_long_mode(&vmx->vcpu))
@@ -1000,7 +972,7 @@ static void guest_write_tsc(u64 guest_tsc, u64 host_tsc)
 static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
 {
         u64 data;
-        struct kvm_msr_entry *msr;
+        struct shared_msr_entry *msr;
 
         if (!pdata) {
                 printk(KERN_ERR "BUG: get_msr called with NULL pdata\n");
@@ -1019,9 +991,9 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
                 vmx_load_host_state(to_vmx(vcpu));
                 data = to_vmx(vcpu)->msr_guest_kernel_gs_base;
                 break;
+#endif
         case MSR_EFER:
                 return kvm_get_msr_common(vcpu, msr_index, pdata);
-#endif
         case MSR_IA32_TSC:
                 data = guest_read_tsc();
                 break;
@@ -1035,6 +1007,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
                 data = vmcs_readl(GUEST_SYSENTER_ESP);
                 break;
         default:
+                vmx_load_host_state(to_vmx(vcpu));
                 msr = find_msr_entry(to_vmx(vcpu), msr_index);
                 if (msr) {
                         vmx_load_host_state(to_vmx(vcpu));
@@ -1056,7 +1029,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
 static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
 {
         struct vcpu_vmx *vmx = to_vmx(vcpu);
-        struct kvm_msr_entry *msr;
+        struct shared_msr_entry *msr;
         u64 host_tsc;
         int ret = 0;
 
@@ -1565,7 +1538,10 @@ continue_rmode:
 static void vmx_set_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
         struct vcpu_vmx *vmx = to_vmx(vcpu);
-        struct kvm_msr_entry *msr = find_msr_entry(vmx, MSR_EFER);
+        struct shared_msr_entry *msr = find_msr_entry(vmx, MSR_EFER);
+
+        if (!msr)
+                return;
 
         /*
          * Force kernel_gs_base reloading before EFER changes, as control
@@ -2417,10 +2393,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
                 if (wrmsr_safe(index, data_low, data_high) < 0)
                         continue;
                 data = data_low | ((u64)data_high << 32);
-                vmx->host_msrs[j].index = index;
-                vmx->host_msrs[j].reserved = 0;
-                vmx->host_msrs[j].data = data;
-                vmx->guest_msrs[j] = vmx->host_msrs[j];
+                vmx->guest_msrs[j].index = i;
+                vmx->guest_msrs[j].data = 0;
                 ++vmx->nmsrs;
         }
 
@@ -3821,7 +3795,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
                 __clear_bit(vmx->vpid, vmx_vpid_bitmap);
         spin_unlock(&vmx_vpid_lock);
         vmx_free_vmcs(vcpu);
-        kfree(vmx->host_msrs);
         kfree(vmx->guest_msrs);
         kvm_vcpu_uninit(vcpu);
         kmem_cache_free(kvm_vcpu_cache, vmx);
@@ -3848,10 +3821,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
                 goto uninit_vcpu;
         }
 
-        vmx->host_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL);
-        if (!vmx->host_msrs)
-                goto free_guest_msrs;
-
         vmx->vmcs = alloc_vmcs();
         if (!vmx->vmcs)
                 goto free_msrs;
@@ -3882,8 +3851,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 free_vmcs:
         free_vmcs(vmx->vmcs);
 free_msrs:
-        kfree(vmx->host_msrs);
-free_guest_msrs:
         kfree(vmx->guest_msrs);
 uninit_vcpu:
         kvm_vcpu_uninit(&vmx->vcpu);
@@ -4033,7 +4000,12 @@ static struct kvm_x86_ops vmx_x86_ops = {
 
 static int __init vmx_init(void)
 {
-        int r;
+        int r, i;
+
+        rdmsrl_safe(MSR_EFER, &host_efer);
+
+        for (i = 0; i < NR_VMX_MSR; ++i)
+                kvm_define_shared_msr(i, vmx_msr_index[i]);
 
         vmx_io_bitmap_a = (unsigned long *)__get_free_page(GFP_KERNEL);
         if (!vmx_io_bitmap_a)