Commit-ID: 0b9f6c4615c993d2b552e0d2bd1ade49b56e5beb Gitweb: http://git.kernel.org/tip/0b9f6c4615c993d2b552e0d2bd1ade49b56e5beb Author: Pan Xinhui <[email protected]> AuthorDate: Wed, 2 Nov 2016 05:08:35 -0400 Committer: Ingo Molnar <[email protected]> CommitDate: Tue, 22 Nov 2016 12:48:08 +0100
x86/kvm: Support the vCPU preemption check Support the vcpu_is_preempted() functionality under KVM. This will enhance lock performance on overcommitted hosts (more runnable vCPUs than physical CPUs in the system) as doing busy waits for preempted vCPUs will hurt system performance far worse than early yielding. Use struct kvm_steal_time::preempted to indicate that if a vCPU is running or not. Signed-off-by: Pan Xinhui <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Paolo Bonzini <[email protected]> Cc: [email protected] Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] [ Typo fixes. ] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/uapi/asm/kvm_para.h | 4 +++- arch/x86/kvm/x86.c | 16 ++++++++++++++++ 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index 94dc8ca..1421a65 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -45,7 +45,9 @@ struct kvm_steal_time { __u64 steal; __u32 version; __u32 flags; - __u32 pad[12]; + __u8 preempted; + __u8 u8_pad[3]; + __u32 pad[11]; }; #define KVM_STEAL_ALIGNMENT_BITS 5 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 04c5d96..59c2d6f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2071,6 +2071,8 @@ static void record_steal_time(struct kvm_vcpu *vcpu) &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) return; + vcpu->arch.st.steal.preempted = 0; + if (vcpu->arch.st.steal.version & 1) vcpu->arch.st.steal.version += 1; /* first time write, random junk */ @@ -2826,8 +2828,22 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); } +static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) +{ + if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) + return; + + vcpu->arch.st.steal.preempted = 1; + + kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime, + &vcpu->arch.st.steal.preempted, + offsetof(struct kvm_steal_time, preempted), + sizeof(vcpu->arch.st.steal.preempted)); +} + void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) { + kvm_steal_time_set_preempted(vcpu); kvm_x86_ops->vcpu_put(vcpu); kvm_put_guest_fpu(vcpu); vcpu->arch.last_host_tsc = rdtsc();
