From 25c5f225beda4fbea878ed8b6203ab4ecc7de2d1 Mon Sep 17 00:00:00 2001 From: Sheng Yang Date: Fri, 28 Mar 2008 13:18:56 +0800 Subject: [PATCH] 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: Sheng Yang Signed-off-by: Avi Kivity --- arch/x86/kvm/vmx.c | 67 +++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 60 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index cbca46acfac..87eee7a7f16 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -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); -- 2.20.1