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KVM: X86: Improve latency for single target IPI fastpath

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IPI and Timer cause the main MSRs write vmexits in cloud environment
observation, let's optimize virtual IPI latency more aggressively to
inject target IPI as soon as possible.

Running kvm-unit-tests/vmexit.flat IPI testing on SKX server, disable
adaptive advance lapic timer and adaptive halt-polling to avoid the
interference, this patch can give another 7% improvement.

w/o fastpath   -> x86.c fastpath      4238 -> 3543  16.4%
x86.c fastpath -> vmx.c fastpath      3543 -> 3293     7%
w/o fastpath   -> vmx.c fastpath      4238 -> 3293  22.3%

Cc: Haiwei Li <lihaiwei@tencent.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200410174703.1138-3-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wanpeng Li
2020-04-10 10:47:03 -07:00
committed by Paolo Bonzini
parent 873e1da169
commit a9ab13ff6e
4 changed files with 34 additions and 23 deletions
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5
arch/x86/include/asm/kvm_host.h
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@@ -1126,7 +1126,7 @@ struct kvm_x86_ops {
*/
void (*tlb_flush_guest)(struct kvm_vcpu *vcpu);
void (*run)(struct kvm_vcpu *vcpu);
enum exit_fastpath_completion (*run)(struct kvm_vcpu *vcpu);
int (*handle_exit)(struct kvm_vcpu *vcpu,
enum exit_fastpath_completion exit_fastpath);
int (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);
@@ -1176,8 +1176,7 @@ struct kvm_x86_ops {
struct x86_instruction_info *info,
enum x86_intercept_stage stage,
struct x86_exception *exception);
void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu,
enum exit_fastpath_completion *exit_fastpath);
void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu);
int (*check_nested_events)(struct kvm_vcpu *vcpu);
void (*request_immediate_exit)(struct kvm_vcpu *vcpu);