[PATCH v6 08/11] x86, kvm/x86.c: support vcpu preempted check
flat view
STALE3638d
SUPERSEDED
From: Pan Xinhui <hidden>
Date: 2016-10-28 04:26:13
Also in:
kvm, linux-s390, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), kvm paravirt (kvm/paravirt), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Revision v6 of 8 in this series.
Revisions (8)
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 one field of struct kvm_steal_time ::preempted to indicate that if one vcpu is running or not. Signed-off-by: Pan Xinhui <redacted> --- 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 e375235..f06e115 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c@@ -2057,6 +2057,8 @@ 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 */
@@ -2810,8 +2812,22 @@ 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();
--
2.4.11