Avi Kivity wrote: > Dong, Eddie wrote: >> Avi: >> >> This patch is to avoid saving and restoring of msr_efer on >> lightweight vmexit. >> >> With this patch, the Kernel build get 10% increasement for 64bits >> on 64 bits, and 5-8% increasement for 32bits on 64 bits. >> Vmexit.flat can see ~1185 cycles save for 64 bits on 64 bits, which >> is 29% save of total VM Exit. It can save ~1206 cycles for 32bits >> on 64bits, which is >> 27.5% save of total. >> BTW, I use 4 core clovertown processor, the total VM Exit time >> reported by vmexit.flat is about 2860 cycles now. >> >> > > Very impressive speedup! > > Comments below. >
Here is the reformatted one, with the patch 64bits guest Kernel Build
performance
on my platform exceeds Xen by ~7%.
BTW, the previous fix for typo is a predendency.
kvm.h | 2 ++
kvm_main.c | 23 +++++++++++++++++++++++
vmx.c | 56
++++++++++++++++++++++++++++++++++++++------------------
3 files changed, 63 insertions(+), 18 deletions(-)
commit 7d3596f123f95d168bbd1721c5d74bf7b13d0099
Author: root <[EMAIL PROTECTED](none)>
Date: Sun May 20 21:35:07 2007 +0800
KVM: VMX: Avoid saving and restoring msr_efer on lightweight
vmexit
MSR_EFER.LME/LMA bits are automatically save/restored by VMX
hardware, KVM only needs to save NX/SCE bits at time of heavy
weight VM Exit. But clearing NX bits in host envirnment may
cause system hang if the host page table is using EXB bits,
thus we leave NX bits as it is. If Host NX=1 and guest NX=0, we
can do guest page table EXB bits check before inserting a shadow
pte (though no guest is expecting to see this kind of gp fault).
If host NX=0, we present guest no Execute-Disable feature to
guest,
thus no host NX=0, guest NX=1 combination.
Signed-off-by: Yaozu (Eddie) Dong <[EMAIL PROTECTED]>
diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 5f056d9..e35434b 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -254,6 +254,7 @@ struct kvm_stat {
u32 request_irq_exits;
u32 irq_exits;
u32 light_exits;
+ u32 efer_reload;
};
struct kvm_vcpu {
@@ -288,6 +289,7 @@ struct kvm_vcpu {
u64 ia32_misc_enable_msr;
int nmsrs;
int save_nmsrs;
+ int msr_offset_efer;
#ifdef CONFIG_X86_64
int msr_offset_kernel_gs_base;
#endif
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 1288cff..a2ac108 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -72,6 +72,7 @@ static struct kvm_stats_debugfs_item {
{ "request_irq", STAT_OFFSET(request_irq_exits) },
{ "irq_exits", STAT_OFFSET(irq_exits) },
{ "light_exits", STAT_OFFSET(light_exits) },
+ { "efer_reload", STAT_OFFSET(efer_reload) },
{ NULL }
};
@@ -2377,6 +2378,27 @@ out:
return r;
}
+static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu)
+{
+ u64 efer;
+ int i;
+ struct kvm_cpuid_entry *e, *entry;
+
+ rdmsrl(MSR_EFER, efer);
+ entry = NULL;
+ for (i = 0; i < vcpu->cpuid_nent; ++i) {
+ e = &vcpu->cpuid_entries[i];
+ if (e->function == 0x80000001) {
+ entry = e;
+ break;
+ }
+ }
+ if (entry && (entry->edx & EFER_NX) && !(efer & EFER_NX)) {
+ entry->edx &= ~(1<<20);
+ printk(KERN_INFO ": guest NX capibility removed\n");
+ }
+}
+
static int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
struct kvm_cpuid *cpuid,
struct kvm_cpuid_entry __user
*entries)
@@ -2391,6 +2413,7 @@ static int kvm_vcpu_ioctl_set_cpuid(struct
kvm_vcpu *vcpu,
cpuid->nent * sizeof(struct
kvm_cpuid_entry)))
goto out;
vcpu->cpuid_nent = cpuid->nent;
+ cpuid_fix_nx_cap(vcpu);
return 0;
out:
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index 9bf8c04..aad5b63 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -41,6 +41,7 @@ static struct page *vmx_io_bitmap_b;
#else
#define HOST_IS_64 0
#endif
+#define EFER_SAVE_RESTORE_BITS EFER_SCE
static struct vmcs_descriptor {
int size;
@@ -56,6 +57,8 @@ static struct vmcs_descriptor {
.ar_bytes = GUEST_##seg##_AR_BYTES, \
}
+#define msr_efer_save_restore_bits(x) ((x).data &
EFER_SAVE_RESTORE_BITS)
+
static struct kvm_vmx_segment_field {
unsigned selector;
unsigned base;
@@ -84,6 +87,13 @@ static const u32 vmx_msr_index[] = {
};
#define NR_VMX_MSR ARRAY_SIZE(vmx_msr_index)
+static inline int msr_efer_need_save_restore(struct kvm_vcpu *vcpu)
+{
+ int efer_offset = vcpu->msr_offset_efer;
+ return msr_efer_save_restore_bits(vcpu->host_msrs[efer_offset])
!=
+
msr_efer_save_restore_bits(vcpu->guest_msrs[efer_offset]);
+}
+
static inline int is_page_fault(u32 intr_info)
{
return (intr_info & (INTR_INFO_INTR_TYPE_MASK |
INTR_INFO_VECTOR_MASK |
@@ -264,6 +274,19 @@ static void reload_tss(void)
#endif
}
+static void load_transition_efer(struct kvm_vcpu *vcpu)
+{
+ u64 trans_efer;
+ int efer_offset = vcpu->msr_offset_efer;
+
+ trans_efer = vcpu->host_msrs[efer_offset].data;
+ trans_efer &= ~EFER_SAVE_RESTORE_BITS;
+ trans_efer |= msr_efer_save_restore_bits(
+ vcpu->guest_msrs[efer_offset]);
+ wrmsrl(MSR_EFER, trans_efer);
+ vcpu->stat.efer_reload++;
+}
+
static void vmx_save_host_state(struct kvm_vcpu *vcpu)
{
struct vmx_host_state *hs = &vcpu->vmx_host_state;
@@ -307,6 +330,8 @@ static void vmx_save_host_state(struct kvm_vcpu
*vcpu)
}
#endif
load_msrs(vcpu->guest_msrs, vcpu->save_nmsrs);
+ if (msr_efer_need_save_restore(vcpu))
+ load_transition_efer(vcpu);
}
static void vmx_load_host_state(struct kvm_vcpu *vcpu)
@@ -335,6 +360,8 @@ static void vmx_load_host_state(struct kvm_vcpu
*vcpu)
}
save_msrs(vcpu->guest_msrs, vcpu->save_nmsrs);
load_msrs(vcpu->host_msrs, vcpu->save_nmsrs);
+ if (msr_efer_need_save_restore(vcpu))
+ load_msrs(vcpu->host_msrs + vcpu->msr_offset_efer, 1);
}
/*
@@ -508,22 +535,7 @@ static void setup_msrs(struct kvm_vcpu *vcpu)
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 + index));
- vmcs_writel(VM_EXIT_MSR_STORE_ADDR,
- virt_to_phys(vcpu->guest_msrs + index));
- vmcs_writel(VM_EXIT_MSR_LOAD_ADDR,
- 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);
+ vcpu->msr_offset_efer = __find_msr_index(vcpu, MSR_EFER);
}
/*
@@ -610,10 +622,15 @@ 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 vmx_msr_entry *msr;
+ int ret;
+
switch (msr_index) {
#ifdef CONFIG_X86_64
case MSR_EFER:
- return kvm_set_msr_common(vcpu, msr_index, data);
+ ret = kvm_set_msr_common(vcpu, msr_index, data);
+ if (vcpu->vmx_host_state.loaded)
+ load_transition_efer(vcpu);
+ return ret;
case MSR_FS_BASE:
vmcs_writel(GUEST_FS_BASE, data);
break;
@@ -638,7 +655,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32
msr_index, u64 data)
if (msr) {
msr->data = data;
if (vcpu->vmx_host_state.loaded)
-
load_msrs(vcpu->guest_msrs,vcpu->save_nmsrs);
+ load_msrs(vcpu->guest_msrs,
vcpu->save_nmsrs);
break;
}
return kvm_set_msr_common(vcpu, msr_index, data);
@@ -1325,6 +1342,9 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
asm ("mov $.Lkvm_vmx_return, %0" : "=g"(kvm_vmx_return));
vmcs_writel(HOST_RIP, kvm_vmx_return); /* 22.2.5 */
+ vmcs_write32(VM_EXIT_MSR_STORE_COUNT, 0);
+ vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, 0);
+ vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, 0);
rdmsr(MSR_IA32_SYSENTER_CS, host_sysenter_cs, junk);
vmcs_write32(HOST_IA32_SYSENTER_CS, host_sysenter_cs);
efer55.patch
Description: efer55.patch
------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/
_______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
