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KVM: VMX: Enable MSR Bitmap feature

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MSR Bitmap controls whether the accessing of an MSR causes VM Exit.
Eliminating exits on automatically saved and restored MSRs yields a
small performance gain.

Signed-off-by: Sheng Yang <sheng.yang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Sheng Yang 2008-03-28 13:18:56 +08:00 committed by Avi Kivity
parent e976a2b997
commit 25c5f225be
1 changed files with 60 additions and 7 deletions
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67
arch/x86/kvm/vmx.c
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@ -91,6 +91,7 @@ static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
static struct page *vmx_io_bitmap_a;
static struct page *vmx_io_bitmap_b;
static struct page *vmx_msr_bitmap;
static DECLARE_BITMAP(vmx_vpid_bitmap, VMX_NR_VPIDS);
static DEFINE_SPINLOCK(vmx_vpid_lock);
@ -185,6 +186,11 @@ static inline int is_external_interrupt(u32 intr_info)
== (INTR_TYPE_EXT_INTR | INTR_INFO_VALID_MASK);
}
static inline int cpu_has_vmx_msr_bitmap(void)
{
return (vmcs_config.cpu_based_exec_ctrl & CPU_BASED_USE_MSR_BITMAPS);
}
static inline int cpu_has_vmx_tpr_shadow(void)
{
return (vmcs_config.cpu_based_exec_ctrl & CPU_BASED_TPR_SHADOW);
@ -1001,6 +1007,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
CPU_BASED_MOV_DR_EXITING |
CPU_BASED_USE_TSC_OFFSETING;
opt = CPU_BASED_TPR_SHADOW |
CPU_BASED_USE_MSR_BITMAPS |
CPU_BASED_ACTIVATE_SECONDARY_CONTROLS;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_PROCBASED_CTLS,
&_cpu_based_exec_control) < 0)
@ -1575,6 +1582,30 @@ static void allocate_vpid(struct vcpu_vmx *vmx)
spin_unlock(&vmx_vpid_lock);
}
void vmx_disable_intercept_for_msr(struct page *msr_bitmap, u32 msr)
{
void *va;
if (!cpu_has_vmx_msr_bitmap())
return;
/*
* See Intel PRM Vol. 3, 20.6.9 (MSR-Bitmap Address). Early manuals
* have the write-low and read-high bitmap offsets the wrong way round.
* We can control MSRs 0x00000000-0x00001fff and 0xc0000000-0xc0001fff.
*/
va = kmap(msr_bitmap);
if (msr <= 0x1fff) {
__clear_bit(msr, va + 0x000); /* read-low */
__clear_bit(msr, va + 0x800); /* write-low */
} else if ((msr >= 0xc0000000) && (msr <= 0xc0001fff)) {
msr &= 0x1fff;
__clear_bit(msr, va + 0x400); /* read-high */
__clear_bit(msr, va + 0xc00); /* write-high */
}
kunmap(msr_bitmap);
}
/*
* Sets up the vmcs for emulated real mode.
*/
@ -1592,6 +1623,9 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
vmcs_write64(IO_BITMAP_A, page_to_phys(vmx_io_bitmap_a));
vmcs_write64(IO_BITMAP_B, page_to_phys(vmx_io_bitmap_b));
if (cpu_has_vmx_msr_bitmap())
vmcs_write64(MSR_BITMAP, page_to_phys(vmx_msr_bitmap));
vmcs_write64(VMCS_LINK_POINTER, -1ull); /* 22.3.1.5 */
/* Control */
@ -2728,7 +2762,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
static int __init vmx_init(void)
{
void *iova;
void *va;
int r;
vmx_io_bitmap_a = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
@ -2741,30 +2775,48 @@ static int __init vmx_init(void)
goto out;
}
vmx_msr_bitmap = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
if (!vmx_msr_bitmap) {
r = -ENOMEM;
goto out1;
}
/*
* Allow direct access to the PC debug port (it is often used for I/O
* delays, but the vmexits simply slow things down).
*/
iova = kmap(vmx_io_bitmap_a);
memset(iova, 0xff, PAGE_SIZE);
clear_bit(0x80, iova);
va = kmap(vmx_io_bitmap_a);
memset(va, 0xff, PAGE_SIZE);
clear_bit(0x80, va);
kunmap(vmx_io_bitmap_a);
iova = kmap(vmx_io_bitmap_b);
memset(iova, 0xff, PAGE_SIZE);
va = kmap(vmx_io_bitmap_b);
memset(va, 0xff, PAGE_SIZE);
kunmap(vmx_io_bitmap_b);
va = kmap(vmx_msr_bitmap);
memset(va, 0xff, PAGE_SIZE);
kunmap(vmx_msr_bitmap);
set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */
r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx), THIS_MODULE);
if (r)
goto out1;
goto out2;
vmx_disable_intercept_for_msr(vmx_msr_bitmap, MSR_FS_BASE);
vmx_disable_intercept_for_msr(vmx_msr_bitmap, MSR_GS_BASE);
vmx_disable_intercept_for_msr(vmx_msr_bitmap, MSR_IA32_SYSENTER_CS);
vmx_disable_intercept_for_msr(vmx_msr_bitmap, MSR_IA32_SYSENTER_ESP);
vmx_disable_intercept_for_msr(vmx_msr_bitmap, MSR_IA32_SYSENTER_EIP);
if (bypass_guest_pf)
kvm_mmu_set_nonpresent_ptes(~0xffeull, 0ull);
return 0;
out2:
__free_page(vmx_msr_bitmap);
out1:
__free_page(vmx_io_bitmap_b);
out:
@ -2774,6 +2826,7 @@ out:
static void __exit vmx_exit(void)
{
__free_page(vmx_msr_bitmap);
__free_page(vmx_io_bitmap_b);
__free_page(vmx_io_bitmap_a);