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authorVitaly Kuznetsov <vkuznets@redhat.com>2018-04-16 12:50:33 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2018-05-14 18:14:24 +0200
commitceef7d10dfb6284d512c499292e6daa35ea83f90 (patch)
tree74fbad9d2b9652ed91deaba9630478e57b538572 /arch/x86/include/asm
parentkvm: x86: Refactor mmu_free_roots() (diff)
downloadlinux-ceef7d10dfb6284d512c499292e6daa35ea83f90.tar.xz
linux-ceef7d10dfb6284d512c499292e6daa35ea83f90.zip
KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support
Enlightened MSR-Bitmap is a natural extension of Enlightened VMCS: Hyper-V Top Level Functional Specification states: "The L1 hypervisor may collaborate with the L0 hypervisor to make MSR accesses more efficient. It can enable enlightened MSR bitmaps by setting the corresponding field in the enlightened VMCS to 1. When enabled, the L0 hypervisor does not monitor the MSR bitmaps for changes. Instead, the L1 hypervisor must invalidate the corresponding clean field after making changes to one of the MSR bitmaps." I reached out to Hyper-V team for additional details and I got the following information: "Current Hyper-V implementation works as following: If the enlightened MSR bitmap is not enabled: - All MSR accesses of L2 guests cause physical VM-Exits If the enlightened MSR bitmap is enabled: - Physical VM-Exits for L2 accesses to certain MSRs (currently FS_BASE, GS_BASE and KERNEL_GS_BASE) are avoided, thus making these MSR accesses faster." I tested my series with a tight rdmsrl loop in L2, for KERNEL_GS_BASE the results are: Without Enlightened MSR-Bitmap: 1300 cycles/read With Enlightened MSR-Bitmap: 120 cycles/read Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Tested-by: Lan Tianyu <Tianyu.Lan@microsoft.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/include/asm')
-rw-r--r--arch/x86/include/asm/hyperv-tlfs.h9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 416cb0e0c496..a8897615354e 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -303,6 +303,9 @@ struct ms_hyperv_tsc_page {
/* TSC emulation after migration */
#define HV_X64_MSR_REENLIGHTENMENT_CONTROL 0x40000106
+/* Nested features (CPUID 0x4000000A) EAX */
+#define HV_X64_NESTED_MSR_BITMAP BIT(19)
+
struct hv_reenlightenment_control {
__u64 vector:8;
__u64 reserved1:8;
@@ -668,7 +671,11 @@ struct hv_enlightened_vmcs {
u32 hv_clean_fields;
u32 hv_padding_32;
u32 hv_synthetic_controls;
- u32 hv_enlightenments_control;
+ struct {
+ u32 nested_flush_hypercall:1;
+ u32 msr_bitmap:1;
+ u32 reserved:30;
+ } hv_enlightenments_control;
u32 hv_vp_id;
u64 hv_vm_id;