| Message ID | 20220624154552.2736417-1-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nVMX: clean up posted interrupt descriptor try_cmpxchg | expand |
On Fri, Jun 24, 2022 at 5:45 PM Paolo Bonzini <pbonzini@redhat.com> wrote: > > Rely on try_cmpxchg64 for re-reading the PID on failure, using READ_ONCE > only right before the first iteration. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kvm/vmx/posted_intr.c | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c > index 73f60aa480fe..1b56c5e5c9fb 100644 > --- a/arch/x86/kvm/vmx/posted_intr.c > +++ b/arch/x86/kvm/vmx/posted_intr.c > @@ -34,7 +34,7 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu) > return &(to_vmx(vcpu)->pi_desc); > } > > -static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) > +static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new) > { > /* > * PID.ON can be set at any time by a different vCPU or by hardware, > @@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) > * update must be retried with a fresh snapshot an ON change causes > * the cmpxchg to fail. > */ > - if (!try_cmpxchg64(&pi_desc->control, &old, new)) > + if (!try_cmpxchg64(&pi_desc->control, pold, new)) > return -EBUSY; > > return 0; > @@ -96,8 +96,9 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) > if (!x2apic_mode) > dest = (dest << 8) & 0xFF00; > > + old.control = READ_ONCE(pi_desc->control); > do { > - old.control = new.control = READ_ONCE(pi_desc->control); > + new.control = old.control; > > /* > * Clear SN (as above) and refresh the destination APIC ID to > @@ -111,7 +112,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) > * descriptor was modified on "put" to use the wakeup vector. > */ > new.nv = POSTED_INTR_VECTOR; > - } while (pi_try_set_control(pi_desc, old.control, new.control)); > + } while (pi_try_set_control(pi_desc, &old.control, new.control)); > > local_irq_restore(flags); > > @@ -156,12 +157,12 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu) > > WARN(pi_desc->sn, "PI descriptor SN field set before blocking"); > > + old.control = READ_ONCE(pi_desc->control); > do { > - old.control = new.control = READ_ONCE(pi_desc->control); > - > /* set 'NV' to 'wakeup vector' */ > + new.control = old.control; This assignment should be above the comment, similar to vmx_vcpu_pi_load. Uros. > new.nv = POSTED_INTR_WAKEUP_VECTOR; > - } while (pi_try_set_control(pi_desc, old.control, new.control)); > + } while (pi_try_set_control(pi_desc, &old.control, new.control)); > > /* > * Send a wakeup IPI to this CPU if an interrupt may have been posted > -- > 2.31.1 >
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 73f60aa480fe..1b56c5e5c9fb 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -34,7 +34,7 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu) return &(to_vmx(vcpu)->pi_desc); } -static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) +static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new) { /* * PID.ON can be set at any time by a different vCPU or by hardware, @@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) * update must be retried with a fresh snapshot an ON change causes * the cmpxchg to fail. */ - if (!try_cmpxchg64(&pi_desc->control, &old, new)) + if (!try_cmpxchg64(&pi_desc->control, pold, new)) return -EBUSY; return 0; @@ -96,8 +96,9 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) if (!x2apic_mode) dest = (dest << 8) & 0xFF00; + old.control = READ_ONCE(pi_desc->control); do { - old.control = new.control = READ_ONCE(pi_desc->control); + new.control = old.control; /* * Clear SN (as above) and refresh the destination APIC ID to @@ -111,7 +112,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) * descriptor was modified on "put" to use the wakeup vector. */ new.nv = POSTED_INTR_VECTOR; - } while (pi_try_set_control(pi_desc, old.control, new.control)); + } while (pi_try_set_control(pi_desc, &old.control, new.control)); local_irq_restore(flags); @@ -156,12 +157,12 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu) WARN(pi_desc->sn, "PI descriptor SN field set before blocking"); + old.control = READ_ONCE(pi_desc->control); do { - old.control = new.control = READ_ONCE(pi_desc->control); - /* set 'NV' to 'wakeup vector' */ + new.control = old.control; new.nv = POSTED_INTR_WAKEUP_VECTOR; - } while (pi_try_set_control(pi_desc, old.control, new.control)); + } while (pi_try_set_control(pi_desc, &old.control, new.control)); /* * Send a wakeup IPI to this CPU if an interrupt may have been posted
Rely on try_cmpxchg64 for re-reading the PID on failure, using READ_ONCE only right before the first iteration. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/vmx/posted_intr.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)