Re: [PATCH v2 7/9] KVM: arm/arm64: PMU: remove request-less vcpu kick
On Tue, Apr 04, 2017 at 08:29:18PM +0200, Andrew Jones wrote:
> On Tue, Apr 04, 2017 at 07:46:12PM +0200, Christoffer Dall wrote:
> > On Fri, Mar 31, 2017 at 06:06:56PM +0200, Andrew Jones wrote:
> > > Refactor PMU overflow handling in order to remove the request-less
> > > vcpu kick. Now, since kvm_vgic_inject_irq() uses vcpu requests,
> > > there should be no chance that a kick sent at just the wrong time
> > > (between the VCPU's call to kvm_pmu_flush_hwstate() and before it
> > > enters guest mode) results in a failure for the guest to see updated
> > > GIC state until its next exit some time later for some other reason.
> > >
> > > Signed-off-by: Andrew Jones
> > > ---
> > > virt/kvm/arm/pmu.c | 29 +++--
> > > 1 file changed, 15 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> > > index 69ccce308458..9d725f3afb11 100644
> > > --- a/virt/kvm/arm/pmu.c
> > > +++ b/virt/kvm/arm/pmu.c
> > > @@ -203,6 +203,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu
> > > *vcpu)
> > > return reg;
> > > }
> > >
> > > +static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
> > > +{
> > > + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> > > + bool overflow;
> > > +
> > > + overflow = !!kvm_pmu_overflow_status(vcpu);
> > > + if (pmu->irq_level != overflow) {
> > > + pmu->irq_level = overflow;
> > > + kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> > > + pmu->irq_num, overflow);
> > > + }
> > > +}
> > > +
> >
> > If we are changing the way the PMU works to adjust the interrupt
> > signaling whenever the PMU changes its internal state, do we still ahv
> > to call kvm_pmu_update_state() from each flush/sync path now?
>
> The thought crossed my mind to rework that completely, in order to remove
> that flush/sync, but then went for the smaller patch for this series. I
> can take a look at it though.
>
Actually, now when I actually read what this code will be doing, the
extra thing in flush/sync won't do any work because it will find that
omu->irq_level == overflow, so never mind - we can improve that later as
an optimization patch.
Let's focus on getting it right.
Thanks,
-Christoffer
> >
> > > /**
> > > * kvm_pmu_overflow_set - set PMU overflow interrupt
> > > * @vcpu: The vcpu pointer
> > > @@ -210,31 +223,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu
> > > *vcpu)
> > > */
> > > void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
> > > {
> > > - u64 reg;
> > > -
> > > if (val == 0)
> > > return;
> > >
> > > vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
> > > - reg = kvm_pmu_overflow_status(vcpu);
> > > - if (reg != 0)
> > > - kvm_vcpu_kick(vcpu);
> > > + kvm_pmu_check_overflow(vcpu);
> > > }
> > >
> > > static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
> > > {
> > > - struct kvm_pmu *pmu = &vcpu->arch.pmu;
> > > - bool overflow;
> > > -
> > > if (!kvm_arm_pmu_v3_ready(vcpu))
> > > return;
> > >
> > > - overflow = !!kvm_pmu_overflow_status(vcpu);
> > > - if (pmu->irq_level != overflow) {
> > > - pmu->irq_level = overflow;
> > > - kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> > > - pmu->irq_num, overflow);
> > > - }
> > > + kvm_pmu_check_overflow(vcpu);
> > > }
> > >
> > > /**
> > > --
> > > 2.9.3
> > >
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Re: [PATCH v2 7/9] KVM: arm/arm64: PMU: remove request-less vcpu kick
On Tue, Apr 04, 2017 at 07:46:12PM +0200, Christoffer Dall wrote:
> On Fri, Mar 31, 2017 at 06:06:56PM +0200, Andrew Jones wrote:
> > Refactor PMU overflow handling in order to remove the request-less
> > vcpu kick. Now, since kvm_vgic_inject_irq() uses vcpu requests,
> > there should be no chance that a kick sent at just the wrong time
> > (between the VCPU's call to kvm_pmu_flush_hwstate() and before it
> > enters guest mode) results in a failure for the guest to see updated
> > GIC state until its next exit some time later for some other reason.
> >
> > Signed-off-by: Andrew Jones
> > ---
> > virt/kvm/arm/pmu.c | 29 +++--
> > 1 file changed, 15 insertions(+), 14 deletions(-)
> >
> > diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> > index 69ccce308458..9d725f3afb11 100644
> > --- a/virt/kvm/arm/pmu.c
> > +++ b/virt/kvm/arm/pmu.c
> > @@ -203,6 +203,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu
> > *vcpu)
> > return reg;
> > }
> >
> > +static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
> > +{
> > + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> > + bool overflow;
> > +
> > + overflow = !!kvm_pmu_overflow_status(vcpu);
> > + if (pmu->irq_level != overflow) {
> > + pmu->irq_level = overflow;
> > + kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> > + pmu->irq_num, overflow);
> > + }
> > +}
> > +
>
> If we are changing the way the PMU works to adjust the interrupt
> signaling whenever the PMU changes its internal state, do we still ahv
> to call kvm_pmu_update_state() from each flush/sync path now?
The thought crossed my mind to rework that completely, in order to remove
that flush/sync, but then went for the smaller patch for this series. I
can take a look at it though.
Thanks,
drew
>
> > /**
> > * kvm_pmu_overflow_set - set PMU overflow interrupt
> > * @vcpu: The vcpu pointer
> > @@ -210,31 +223,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu
> > *vcpu)
> > */
> > void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
> > {
> > - u64 reg;
> > -
> > if (val == 0)
> > return;
> >
> > vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
> > - reg = kvm_pmu_overflow_status(vcpu);
> > - if (reg != 0)
> > - kvm_vcpu_kick(vcpu);
> > + kvm_pmu_check_overflow(vcpu);
> > }
> >
> > static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
> > {
> > - struct kvm_pmu *pmu = &vcpu->arch.pmu;
> > - bool overflow;
> > -
> > if (!kvm_arm_pmu_v3_ready(vcpu))
> > return;
> >
> > - overflow = !!kvm_pmu_overflow_status(vcpu);
> > - if (pmu->irq_level != overflow) {
> > - pmu->irq_level = overflow;
> > - kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> > - pmu->irq_num, overflow);
> > - }
> > + kvm_pmu_check_overflow(vcpu);
> > }
> >
> > /**
> > --
> > 2.9.3
> >
>
> Thanks,
> -Christoffer
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Re: [PATCH v2 7/9] KVM: arm/arm64: PMU: remove request-less vcpu kick
On Fri, Mar 31, 2017 at 06:06:56PM +0200, Andrew Jones wrote:
> Refactor PMU overflow handling in order to remove the request-less
> vcpu kick. Now, since kvm_vgic_inject_irq() uses vcpu requests,
> there should be no chance that a kick sent at just the wrong time
> (between the VCPU's call to kvm_pmu_flush_hwstate() and before it
> enters guest mode) results in a failure for the guest to see updated
> GIC state until its next exit some time later for some other reason.
>
> Signed-off-by: Andrew Jones
> ---
> virt/kvm/arm/pmu.c | 29 +++--
> 1 file changed, 15 insertions(+), 14 deletions(-)
>
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 69ccce308458..9d725f3afb11 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -203,6 +203,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
> return reg;
> }
>
> +static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + bool overflow;
> +
> + overflow = !!kvm_pmu_overflow_status(vcpu);
> + if (pmu->irq_level != overflow) {
> + pmu->irq_level = overflow;
> + kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> + pmu->irq_num, overflow);
> + }
> +}
> +
If we are changing the way the PMU works to adjust the interrupt
signaling whenever the PMU changes its internal state, do we still ahv
to call kvm_pmu_update_state() from each flush/sync path now?
> /**
> * kvm_pmu_overflow_set - set PMU overflow interrupt
> * @vcpu: The vcpu pointer
> @@ -210,31 +223,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu
> *vcpu)
> */
> void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
> {
> - u64 reg;
> -
> if (val == 0)
> return;
>
> vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
> - reg = kvm_pmu_overflow_status(vcpu);
> - if (reg != 0)
> - kvm_vcpu_kick(vcpu);
> + kvm_pmu_check_overflow(vcpu);
> }
>
> static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
> {
> - struct kvm_pmu *pmu = &vcpu->arch.pmu;
> - bool overflow;
> -
> if (!kvm_arm_pmu_v3_ready(vcpu))
> return;
>
> - overflow = !!kvm_pmu_overflow_status(vcpu);
> - if (pmu->irq_level != overflow) {
> - pmu->irq_level = overflow;
> - kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> - pmu->irq_num, overflow);
> - }
> + kvm_pmu_check_overflow(vcpu);
> }
>
> /**
> --
> 2.9.3
>
Thanks,
-Christoffer
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[PATCH v2 7/9] KVM: arm/arm64: PMU: remove request-less vcpu kick
Refactor PMU overflow handling in order to remove the request-less
vcpu kick. Now, since kvm_vgic_inject_irq() uses vcpu requests,
there should be no chance that a kick sent at just the wrong time
(between the VCPU's call to kvm_pmu_flush_hwstate() and before it
enters guest mode) results in a failure for the guest to see updated
GIC state until its next exit some time later for some other reason.
Signed-off-by: Andrew Jones
---
virt/kvm/arm/pmu.c | 29 +++--
1 file changed, 15 insertions(+), 14 deletions(-)
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 69ccce308458..9d725f3afb11 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -203,6 +203,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
return reg;
}
+static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
+{
+ struct kvm_pmu *pmu = &vcpu->arch.pmu;
+ bool overflow;
+
+ overflow = !!kvm_pmu_overflow_status(vcpu);
+ if (pmu->irq_level != overflow) {
+ pmu->irq_level = overflow;
+ kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
+ pmu->irq_num, overflow);
+ }
+}
+
/**
* kvm_pmu_overflow_set - set PMU overflow interrupt
* @vcpu: The vcpu pointer
@@ -210,31 +223,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
*/
void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
{
- u64 reg;
-
if (val == 0)
return;
vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
- reg = kvm_pmu_overflow_status(vcpu);
- if (reg != 0)
- kvm_vcpu_kick(vcpu);
+ kvm_pmu_check_overflow(vcpu);
}
static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
{
- struct kvm_pmu *pmu = &vcpu->arch.pmu;
- bool overflow;
-
if (!kvm_arm_pmu_v3_ready(vcpu))
return;
- overflow = !!kvm_pmu_overflow_status(vcpu);
- if (pmu->irq_level != overflow) {
- pmu->irq_level = overflow;
- kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
- pmu->irq_num, overflow);
- }
+ kvm_pmu_check_overflow(vcpu);
}
/**
--
2.9.3
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