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KVM: VMX: Enable io bitmaps to avoid IO port 0x80 VMEXITs

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This patch enables IO bitmaps control on vmx and unmask the 0x80 port to
avoid VMEXITs caused by accessing port 0x80. 0x80 is used as delays (see
include/asm/io.h), and handling VMEXITs on its access is unnecessary but
slows things down. This patch improves kernel build test at around
3%~5%.
	Because every VM uses the same io bitmap, it is shared between
all VMs rather than a per-VM data structure.

Signed-off-by: Qing He <qing.he@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
He, Qing 2007-04-30 09:45:24 +03:00 committed by Avi Kivity
parent 8f41958bdd
commit fdef3ad1b3
1 changed files with 46 additions and 4 deletions
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50
drivers/kvm/vmx.c
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@ -34,6 +34,9 @@ MODULE_LICENSE("GPL");
static DEFINE_PER_CPU(struct vmcs *, vmxarea);
static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
static struct page *vmx_io_bitmap_a;
static struct page *vmx_io_bitmap_b;
#ifdef CONFIG_X86_64
#define HOST_IS_64 1
#else
@ -1129,8 +1132,8 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0);
/* I/O */
vmcs_write64(IO_BITMAP_A, 0);
vmcs_write64(IO_BITMAP_B, 0);
vmcs_write64(IO_BITMAP_A, page_to_phys(vmx_io_bitmap_a));
vmcs_write64(IO_BITMAP_B, page_to_phys(vmx_io_bitmap_b));
guest_write_tsc(0);
@ -1150,7 +1153,7 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
CPU_BASED_HLT_EXITING /* 20.6.2 */
| CPU_BASED_CR8_LOAD_EXITING /* 20.6.2 */
| CPU_BASED_CR8_STORE_EXITING /* 20.6.2 */
| CPU_BASED_UNCOND_IO_EXITING /* 20.6.2 */
| CPU_BASED_ACTIVATE_IO_BITMAP /* 20.6.2 */
| CPU_BASED_MOV_DR_EXITING
| CPU_BASED_USE_TSC_OFFSETING /* 21.3 */
);
@ -2188,11 +2191,50 @@ static struct kvm_arch_ops vmx_arch_ops = {
static int __init vmx_init(void)
{
return kvm_init_arch(&vmx_arch_ops, THIS_MODULE);
void *iova;
int r;
vmx_io_bitmap_a = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
if (!vmx_io_bitmap_a)
return -ENOMEM;
vmx_io_bitmap_b = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
if (!vmx_io_bitmap_b) {
r = -ENOMEM;
goto out;
}
/*
* 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);
kunmap(iova);
iova = kmap(vmx_io_bitmap_b);
memset(iova, 0xff, PAGE_SIZE);
kunmap(iova);
r = kvm_init_arch(&vmx_arch_ops, THIS_MODULE);
if (r)
goto out1;
return 0;
out1:
__free_page(vmx_io_bitmap_b);
out:
__free_page(vmx_io_bitmap_a);
return r;
}
static void __exit vmx_exit(void)
{
__free_page(vmx_io_bitmap_b);
__free_page(vmx_io_bitmap_a);
kvm_exit_arch();
}