Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a75beee6e4f5d2f0ae6e28cd626b2f157e93afd2
Commit:     a75beee6e4f5d2f0ae6e28cd626b2f157e93afd2
Parent:     b3f37707b05e9ce82d5bec660e9d0b15452ee9a0
Author:     Eddie Dong <[EMAIL PROTECTED]>
AuthorDate: Thu May 17 18:55:15 2007 +0300
Committer:  Avi Kivity <[EMAIL PROTECTED]>
CommitDate: Mon Jul 16 12:05:41 2007 +0300

    KVM: VMX: Avoid saving and restoring msrs on lightweight vmexit
    
    In a lightweight exit (where we exit and reenter the guest without
    scheduling or exiting to userspace in between), we don't need various
    msrs on the host, and avoiding shuffling them around reduces raw exit
    time by 8%.
    
    i386 compile fix by Daniel Hecken <[EMAIL PROTECTED]>.
    
    Signed-off-by: Yaozu (Eddie) Dong <[EMAIL PROTECTED]>
    Signed-off-by: Avi Kivity <[EMAIL PROTECTED]>
---
 drivers/kvm/kvm.h |    4 ++
 drivers/kvm/vmx.c |  128 ++++++++++++++++++++++++++++++-----------------------
 2 files changed, 76 insertions(+), 56 deletions(-)

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index fc4a6c1..c252efe 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -288,6 +288,10 @@ struct kvm_vcpu {
        u64 apic_base;
        u64 ia32_misc_enable_msr;
        int nmsrs;
+       int save_nmsrs;
+#ifdef CONFIG_X86_64
+       int msr_offset_kernel_gs_base;
+#endif
        struct vmx_msr_entry *guest_msrs;
        struct vmx_msr_entry *host_msrs;
 
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index a05bfa0..872ca03 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -85,19 +85,6 @@ static const u32 vmx_msr_index[] = {
 };
 #define NR_VMX_MSR ARRAY_SIZE(vmx_msr_index)
 
-#ifdef CONFIG_X86_64
-static unsigned msr_offset_kernel_gs_base;
-#define NR_64BIT_MSRS 4
-/*
- * avoid save/load MSR_SYSCALL_MASK and MSR_LSTAR by std vt
- * mechanism (cpu bug AA24)
- */
-#define NR_BAD_MSRS 2
-#else
-#define NR_64BIT_MSRS 0
-#define NR_BAD_MSRS 0
-#endif
-
 static inline int is_page_fault(u32 intr_info)
 {
        return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK |
@@ -118,13 +105,23 @@ static inline int is_external_interrupt(u32 intr_info)
                == (INTR_TYPE_EXT_INTR | INTR_INFO_VALID_MASK);
 }
 
-static struct vmx_msr_entry *find_msr_entry(struct kvm_vcpu *vcpu, u32 msr)
+static int __find_msr_index(struct kvm_vcpu *vcpu, u32 msr)
 {
        int i;
 
        for (i = 0; i < vcpu->nmsrs; ++i)
                if (vcpu->guest_msrs[i].index == msr)
-                       return &vcpu->guest_msrs[i];
+                       return i;
+       return -1;
+}
+
+static struct vmx_msr_entry *find_msr_entry(struct kvm_vcpu *vcpu, u32 msr)
+{
+       int i;
+
+       i = __find_msr_index(vcpu, msr);
+       if (i >= 0)
+               return &vcpu->guest_msrs[i];
        return NULL;
 }
 
@@ -307,10 +304,10 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
 
 #ifdef CONFIG_X86_64
        if (is_long_mode(vcpu)) {
-               save_msrs(vcpu->host_msrs + msr_offset_kernel_gs_base, 1);
-               load_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
+               save_msrs(vcpu->host_msrs + vcpu->msr_offset_kernel_gs_base, 1);
        }
 #endif
+       load_msrs(vcpu->guest_msrs, vcpu->save_nmsrs);
 }
 
 static void vmx_load_host_state(struct kvm_vcpu *vcpu)
@@ -337,12 +334,8 @@ static void vmx_load_host_state(struct kvm_vcpu *vcpu)
 
                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
+       save_msrs(vcpu->guest_msrs, vcpu->save_nmsrs);
+       load_msrs(vcpu->host_msrs, vcpu->save_nmsrs);
 }
 
 /*
@@ -464,41 +457,74 @@ static void vmx_inject_gp(struct kvm_vcpu *vcpu, unsigned 
error_code)
 }
 
 /*
+ * Swap MSR entry in host/guest MSR entry array.
+ */
+void move_msr_up(struct kvm_vcpu *vcpu, int from, int to)
+{
+       struct vmx_msr_entry tmp;
+       tmp = vcpu->guest_msrs[to];
+       vcpu->guest_msrs[to] = vcpu->guest_msrs[from];
+       vcpu->guest_msrs[from] = tmp;
+       tmp = vcpu->host_msrs[to];
+       vcpu->host_msrs[to] = vcpu->host_msrs[from];
+       vcpu->host_msrs[from] = tmp;
+}
+
+/*
  * Set up the vmcs to automatically save and restore system
  * msrs.  Don't touch the 64-bit msrs if the guest is in legacy
  * mode, as fiddling with msrs is very expensive.
  */
 static void setup_msrs(struct kvm_vcpu *vcpu)
 {
-       int nr_skip, nr_good_msrs;
+       int index, save_nmsrs;
 
-       if (is_long_mode(vcpu))
-               nr_skip = NR_BAD_MSRS;
-       else
-               nr_skip = NR_64BIT_MSRS;
-       nr_good_msrs = vcpu->nmsrs - nr_skip;
+       save_nmsrs = 0;
+#ifdef CONFIG_X86_64
+       if (is_long_mode(vcpu)) {
+               index = __find_msr_index(vcpu, MSR_SYSCALL_MASK);
+               if (index >= 0)
+                       move_msr_up(vcpu, index, save_nmsrs++);
+               index = __find_msr_index(vcpu, MSR_LSTAR);
+               if (index >= 0)
+                       move_msr_up(vcpu, index, save_nmsrs++);
+               index = __find_msr_index(vcpu, MSR_CSTAR);
+               if (index >= 0)
+                       move_msr_up(vcpu, index, save_nmsrs++);
+               index = __find_msr_index(vcpu, MSR_KERNEL_GS_BASE);
+               if (index >= 0)
+                       move_msr_up(vcpu, index, save_nmsrs++);
+               /*
+                * MSR_K6_STAR is only needed on long mode guests, and only
+                * if efer.sce is enabled.
+                */
+               index = __find_msr_index(vcpu, MSR_K6_STAR);
+               if ((index >= 0) && (vcpu->shadow_efer & EFER_SCE))
+                       move_msr_up(vcpu, index, save_nmsrs++);
+       }
+#endif
+       vcpu->save_nmsrs = save_nmsrs;
 
-       /*
-        * MSR_K6_STAR is only needed on long mode guests, and only
-        * if efer.sce is enabled.
-        */
-       if (find_msr_entry(vcpu, MSR_K6_STAR)) {
-               --nr_good_msrs;
 #ifdef CONFIG_X86_64
-               if (is_long_mode(vcpu) && (vcpu->shadow_efer & EFER_SCE))
-                       ++nr_good_msrs;
+       vcpu->msr_offset_kernel_gs_base =
+               __find_msr_index(vcpu, MSR_KERNEL_GS_BASE);
 #endif
+       index = __find_msr_index(vcpu, MSR_EFER);
+       if (index >= 0)
+               save_nmsrs = 1;
+       else {
+               save_nmsrs = 0;
+               index = 0;
        }
-
        vmcs_writel(VM_ENTRY_MSR_LOAD_ADDR,
-                   virt_to_phys(vcpu->guest_msrs + nr_skip));
+                   virt_to_phys(vcpu->guest_msrs + index));
        vmcs_writel(VM_EXIT_MSR_STORE_ADDR,
-                   virt_to_phys(vcpu->guest_msrs + nr_skip));
+                   virt_to_phys(vcpu->guest_msrs + index));
        vmcs_writel(VM_EXIT_MSR_LOAD_ADDR,
-                   virt_to_phys(vcpu->host_msrs + nr_skip));
-       vmcs_write32(VM_EXIT_MSR_STORE_COUNT, nr_good_msrs); /* 22.2.2 */
-       vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, nr_good_msrs);  /* 22.2.2 */
-       vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, nr_good_msrs); /* 22.2.2 */
+                   virt_to_phys(vcpu->host_msrs + index));
+       vmcs_write32(VM_EXIT_MSR_STORE_COUNT, save_nmsrs);
+       vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, save_nmsrs);
+       vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, save_nmsrs);
 }
 
 /*
@@ -595,14 +621,6 @@ 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;
-               if (vcpu->vmx_host_state.loaded)
-                       load_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
-               break;
 #endif
        case MSR_IA32_SYSENTER_CS:
                vmcs_write32(GUEST_SYSENTER_CS, data);
@@ -620,6 +638,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 
msr_index, u64 data)
                msr = find_msr_entry(vcpu, msr_index);
                if (msr) {
                        msr->data = data;
+                       if (vcpu->vmx_host_state.loaded)
+                               load_msrs(vcpu->guest_msrs,vcpu->save_nmsrs);
                        break;
                }
                return kvm_set_msr_common(vcpu, msr_index, data);
@@ -1331,10 +1351,6 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
                vcpu->host_msrs[j].reserved = 0;
                vcpu->host_msrs[j].data = data;
                vcpu->guest_msrs[j] = vcpu->host_msrs[j];
-#ifdef CONFIG_X86_64
-               if (index == MSR_KERNEL_GS_BASE)
-                       msr_offset_kernel_gs_base = j;
-#endif
                ++vcpu->nmsrs;
        }
 
-
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