Commit 25c5f225 authored by Sheng Yang's avatar Sheng Yang Committed by Avi Kivity
Browse files

KVM: VMX: Enable MSR Bitmap feature 



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: default avatarSheng Yang <sheng.yang@intel.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent e976a2b9

arch/x86/kvm/vmx.c

+60 −7
Original line number Diff line number Diff line
@@ -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 @@ static int __init vmx_init(void) 


static void __exit vmx_exit(void)

{

	__free_page(vmx_msr_bitmap);

	__free_page(vmx_io_bitmap_b);

	__free_page(vmx_io_bitmap_a);