Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On Mon, Jan 30, 2017 at 1:05 PM, Marc Zyngier wrote:
> On 30/01/17 17:58, Jintack Lim wrote:
>> On Sun, Jan 29, 2017 at 6:54 AM, Marc Zyngier wrote:
>>> On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim
>>> wrote:
Make cntvoff per each timer context. This is helpful to abstract kvm
timer functions to work with timer context without considering timer
types (e.g. physical timer or virtual timer).
This also would pave the way for ever doing adjustments of the cntvoff
on a per-CPU basis if that should ever make sense.
Signed-off-by: Jintack Lim
---
arch/arm/include/asm/kvm_host.h | 6 +++---
arch/arm64/include/asm/kvm_host.h | 4 ++--
include/kvm/arm_arch_timer.h | 8 +++-
virt/kvm/arm/arch_timer.c | 26 --
virt/kvm/arm/hyp/timer-sr.c | 3 +--
5 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h
b/arch/arm/include/asm/kvm_host.h
index d5423ab..f5456a9 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -60,9 +60,6 @@ struct kvm_arch {
/* The last vcpu id that ran on each physical CPU */
int __percpu *last_vcpu_ran;
- /* Timer */
- struct arch_timer_kvm timer;
-
/*
* Anything that is not used directly from assembly code goes
* here.
@@ -75,6 +72,9 @@ struct kvm_arch {
/* Stage-2 page table */
pgd_t *pgd;
+ /* A lock to synchronize cntvoff among all vtimer context of vcpus */
+ spinlock_t cntvoff_lock;
>>>
>>> Is there any condition where we need this to be a spinlock? I would have
>>> thought that a mutex should have been enough, as this should only be
>>> updated on migration or initialization. Not that it matters much in this
>>> case, but I wondered if there is something I'm missing.
>>>
+
/* Interrupt controller */
struct vgic_distvgic;
int max_vcpus;
diff --git a/arch/arm64/include/asm/kvm_host.h
b/arch/arm64/include/asm/kvm_host.h
index e505038..23749a8 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -71,8 +71,8 @@ struct kvm_arch {
/* Interrupt controller */
struct vgic_distvgic;
- /* Timer */
- struct arch_timer_kvm timer;
+ /* A lock to synchronize cntvoff among all vtimer context of vcpus */
+ spinlock_t cntvoff_lock;
};
#define KVM_NR_MEM_OBJS 40
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index daad3c1..1b9c988 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -23,11 +23,6 @@
#include
#include
-struct arch_timer_kvm {
- /* Virtual offset */
- u64 cntvoff;
-};
-
struct arch_timer_context {
/* Registers: control register, timer value */
u32 cnt_ctl;
@@ -38,6 +33,9 @@ struct arch_timer_context {
/* Active IRQ state caching */
boolactive_cleared_last;
+
+ /* Virtual offset */
+ u64 cntvoff;
};
struct arch_timer_cpu {
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 6740efa..fa4c042 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -101,9 +101,10 @@ static void kvm_timer_inject_irq_work(struct
work_struct *work)
static u64 kvm_timer_compute_delta(struct kvm_vcpu *vcpu)
{
u64 cval, now;
+ struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
- cval = vcpu_vtimer(vcpu)->cnt_cval;
- now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
+ cval = vtimer->cnt_cval;
+ now = kvm_phys_timer_read() - vtimer->cntvoff;
if (now < cval) {
u64 ns;
@@ -159,7 +160,7 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
return false;
cval = vtimer->cnt_cval;
- now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
+ now = kvm_phys_timer_read() - vtimer->cntvoff;
return cval <= now;
}
@@ -353,10 +354,23 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
return 0;
}
+/* Make the updates of cntvoff for all vtimer contexts atomic */
+static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
>>>
>>> Arguably, this acts on the VM itself and not a single vcpu. maybe you
>>> should consider passing the struct kvm pointer to reflect this.
>>>
>>
>> Yes, that would be better.
>>
+{
+ in
Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On Sun, Jan 29, 2017 at 6:54 AM, Marc Zyngier wrote:
> On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim
> wrote:
>> Make cntvoff per each timer context. This is helpful to abstract kvm
>> timer functions to work with timer context without considering timer
>> types (e.g. physical timer or virtual timer).
>>
>> This also would pave the way for ever doing adjustments of the cntvoff
>> on a per-CPU basis if that should ever make sense.
>>
>> Signed-off-by: Jintack Lim
>> ---
>> arch/arm/include/asm/kvm_host.h | 6 +++---
>> arch/arm64/include/asm/kvm_host.h | 4 ++--
>> include/kvm/arm_arch_timer.h | 8 +++-
>> virt/kvm/arm/arch_timer.c | 26 --
>> virt/kvm/arm/hyp/timer-sr.c | 3 +--
>> 5 files changed, 29 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/kvm_host.h
>> b/arch/arm/include/asm/kvm_host.h
>> index d5423ab..f5456a9 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -60,9 +60,6 @@ struct kvm_arch {
>> /* The last vcpu id that ran on each physical CPU */
>> int __percpu *last_vcpu_ran;
>>
>> - /* Timer */
>> - struct arch_timer_kvm timer;
>> -
>> /*
>>* Anything that is not used directly from assembly code goes
>>* here.
>> @@ -75,6 +72,9 @@ struct kvm_arch {
>> /* Stage-2 page table */
>> pgd_t *pgd;
>>
>> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
>> + spinlock_t cntvoff_lock;
>
> Is there any condition where we need this to be a spinlock? I would have
> thought that a mutex should have been enough, as this should only be
> updated on migration or initialization. Not that it matters much in this
> case, but I wondered if there is something I'm missing.
>
>> +
>> /* Interrupt controller */
>> struct vgic_distvgic;
>> int max_vcpus;
>> diff --git a/arch/arm64/include/asm/kvm_host.h
>> b/arch/arm64/include/asm/kvm_host.h
>> index e505038..23749a8 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -71,8 +71,8 @@ struct kvm_arch {
>> /* Interrupt controller */
>> struct vgic_distvgic;
>>
>> - /* Timer */
>> - struct arch_timer_kvm timer;
>> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
>> + spinlock_t cntvoff_lock;
>> };
>>
>> #define KVM_NR_MEM_OBJS 40
>> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
>> index daad3c1..1b9c988 100644
>> --- a/include/kvm/arm_arch_timer.h
>> +++ b/include/kvm/arm_arch_timer.h
>> @@ -23,11 +23,6 @@
>> #include
>> #include
>>
>> -struct arch_timer_kvm {
>> - /* Virtual offset */
>> - u64 cntvoff;
>> -};
>> -
>> struct arch_timer_context {
>> /* Registers: control register, timer value */
>> u32 cnt_ctl;
>> @@ -38,6 +33,9 @@ struct arch_timer_context {
>>
>> /* Active IRQ state caching */
>> boolactive_cleared_last;
>> +
>> + /* Virtual offset */
>> + u64 cntvoff;
>> };
>>
>> struct arch_timer_cpu {
>> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
>> index 6740efa..fa4c042 100644
>> --- a/virt/kvm/arm/arch_timer.c
>> +++ b/virt/kvm/arm/arch_timer.c
>> @@ -101,9 +101,10 @@ static void kvm_timer_inject_irq_work(struct
>> work_struct *work)
>> static u64 kvm_timer_compute_delta(struct kvm_vcpu *vcpu)
>> {
>> u64 cval, now;
>> + struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>>
>> - cval = vcpu_vtimer(vcpu)->cnt_cval;
>> - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
>> + cval = vtimer->cnt_cval;
>> + now = kvm_phys_timer_read() - vtimer->cntvoff;
>>
>> if (now < cval) {
>> u64 ns;
>> @@ -159,7 +160,7 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
>> return false;
>>
>> cval = vtimer->cnt_cval;
>> - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
>> + now = kvm_phys_timer_read() - vtimer->cntvoff;
>>
>> return cval <= now;
>> }
>> @@ -353,10 +354,23 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
>> return 0;
>> }
>>
>> +/* Make the updates of cntvoff for all vtimer contexts atomic */
>> +static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
>
> Arguably, this acts on the VM itself and not a single vcpu. maybe you
> should consider passing the struct kvm pointer to reflect this.
>
Yes, that would be better.
>> +{
>> + int i;
>> +
>> + spin_lock(&vcpu->kvm->arch.cntvoff_lock);
>> + kvm_for_each_vcpu(i, vcpu, vcpu->kvm)
>> + vcpu_vtimer(vcpu)->cntvoff = cntvoff;
>> + spin_unlock(&vcpu->kvm->arch.cntvoff_lock);
>> +}
>> +
>> void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
>> {
>> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>>
>> + upda
Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On 30/01/17 17:58, Jintack Lim wrote:
> On Sun, Jan 29, 2017 at 6:54 AM, Marc Zyngier wrote:
>> On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim
>> wrote:
>>> Make cntvoff per each timer context. This is helpful to abstract kvm
>>> timer functions to work with timer context without considering timer
>>> types (e.g. physical timer or virtual timer).
>>>
>>> This also would pave the way for ever doing adjustments of the cntvoff
>>> on a per-CPU basis if that should ever make sense.
>>>
>>> Signed-off-by: Jintack Lim
>>> ---
>>> arch/arm/include/asm/kvm_host.h | 6 +++---
>>> arch/arm64/include/asm/kvm_host.h | 4 ++--
>>> include/kvm/arm_arch_timer.h | 8 +++-
>>> virt/kvm/arm/arch_timer.c | 26 --
>>> virt/kvm/arm/hyp/timer-sr.c | 3 +--
>>> 5 files changed, 29 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/kvm_host.h
>>> b/arch/arm/include/asm/kvm_host.h
>>> index d5423ab..f5456a9 100644
>>> --- a/arch/arm/include/asm/kvm_host.h
>>> +++ b/arch/arm/include/asm/kvm_host.h
>>> @@ -60,9 +60,6 @@ struct kvm_arch {
>>> /* The last vcpu id that ran on each physical CPU */
>>> int __percpu *last_vcpu_ran;
>>>
>>> - /* Timer */
>>> - struct arch_timer_kvm timer;
>>> -
>>> /*
>>>* Anything that is not used directly from assembly code goes
>>>* here.
>>> @@ -75,6 +72,9 @@ struct kvm_arch {
>>> /* Stage-2 page table */
>>> pgd_t *pgd;
>>>
>>> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
>>> + spinlock_t cntvoff_lock;
>>
>> Is there any condition where we need this to be a spinlock? I would have
>> thought that a mutex should have been enough, as this should only be
>> updated on migration or initialization. Not that it matters much in this
>> case, but I wondered if there is something I'm missing.
>>
>>> +
>>> /* Interrupt controller */
>>> struct vgic_distvgic;
>>> int max_vcpus;
>>> diff --git a/arch/arm64/include/asm/kvm_host.h
>>> b/arch/arm64/include/asm/kvm_host.h
>>> index e505038..23749a8 100644
>>> --- a/arch/arm64/include/asm/kvm_host.h
>>> +++ b/arch/arm64/include/asm/kvm_host.h
>>> @@ -71,8 +71,8 @@ struct kvm_arch {
>>> /* Interrupt controller */
>>> struct vgic_distvgic;
>>>
>>> - /* Timer */
>>> - struct arch_timer_kvm timer;
>>> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
>>> + spinlock_t cntvoff_lock;
>>> };
>>>
>>> #define KVM_NR_MEM_OBJS 40
>>> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
>>> index daad3c1..1b9c988 100644
>>> --- a/include/kvm/arm_arch_timer.h
>>> +++ b/include/kvm/arm_arch_timer.h
>>> @@ -23,11 +23,6 @@
>>> #include
>>> #include
>>>
>>> -struct arch_timer_kvm {
>>> - /* Virtual offset */
>>> - u64 cntvoff;
>>> -};
>>> -
>>> struct arch_timer_context {
>>> /* Registers: control register, timer value */
>>> u32 cnt_ctl;
>>> @@ -38,6 +33,9 @@ struct arch_timer_context {
>>>
>>> /* Active IRQ state caching */
>>> boolactive_cleared_last;
>>> +
>>> + /* Virtual offset */
>>> + u64 cntvoff;
>>> };
>>>
>>> struct arch_timer_cpu {
>>> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
>>> index 6740efa..fa4c042 100644
>>> --- a/virt/kvm/arm/arch_timer.c
>>> +++ b/virt/kvm/arm/arch_timer.c
>>> @@ -101,9 +101,10 @@ static void kvm_timer_inject_irq_work(struct
>>> work_struct *work)
>>> static u64 kvm_timer_compute_delta(struct kvm_vcpu *vcpu)
>>> {
>>> u64 cval, now;
>>> + struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>>>
>>> - cval = vcpu_vtimer(vcpu)->cnt_cval;
>>> - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
>>> + cval = vtimer->cnt_cval;
>>> + now = kvm_phys_timer_read() - vtimer->cntvoff;
>>>
>>> if (now < cval) {
>>> u64 ns;
>>> @@ -159,7 +160,7 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
>>> return false;
>>>
>>> cval = vtimer->cnt_cval;
>>> - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
>>> + now = kvm_phys_timer_read() - vtimer->cntvoff;
>>>
>>> return cval <= now;
>>> }
>>> @@ -353,10 +354,23 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
>>> return 0;
>>> }
>>>
>>> +/* Make the updates of cntvoff for all vtimer contexts atomic */
>>> +static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
>>
>> Arguably, this acts on the VM itself and not a single vcpu. maybe you
>> should consider passing the struct kvm pointer to reflect this.
>>
>
> Yes, that would be better.
>
>>> +{
>>> + int i;
>>> +
>>> + spin_lock(&vcpu->kvm->arch.cntvoff_lock);
>>> + kvm_for_each_vcpu(i, vcpu, vcpu->kvm)
>>> + vcpu_vtimer(vcpu)->cntvoff = cntvoff;
>>> + spin_unlock
Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On Mon, Jan 30, 2017 at 9:51 AM, Marc Zyngier wrote:
> On 30/01/17 14:45, Christoffer Dall wrote:
>> On Sun, Jan 29, 2017 at 11:54:05AM +, Marc Zyngier wrote:
>>> On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim
>>> wrote:
Make cntvoff per each timer context. This is helpful to abstract kvm
timer functions to work with timer context without considering timer
types (e.g. physical timer or virtual timer).
This also would pave the way for ever doing adjustments of the cntvoff
on a per-CPU basis if that should ever make sense.
Signed-off-by: Jintack Lim
---
arch/arm/include/asm/kvm_host.h | 6 +++---
arch/arm64/include/asm/kvm_host.h | 4 ++--
include/kvm/arm_arch_timer.h | 8 +++-
virt/kvm/arm/arch_timer.c | 26 --
virt/kvm/arm/hyp/timer-sr.c | 3 +--
5 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h
b/arch/arm/include/asm/kvm_host.h
index d5423ab..f5456a9 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -60,9 +60,6 @@ struct kvm_arch {
/* The last vcpu id that ran on each physical CPU */
int __percpu *last_vcpu_ran;
- /* Timer */
- struct arch_timer_kvm timer;
-
/*
* Anything that is not used directly from assembly code goes
* here.
@@ -75,6 +72,9 @@ struct kvm_arch {
/* Stage-2 page table */
pgd_t *pgd;
+ /* A lock to synchronize cntvoff among all vtimer context of vcpus */
+ spinlock_t cntvoff_lock;
>>>
>>> Is there any condition where we need this to be a spinlock? I would have
>>> thought that a mutex should have been enough, as this should only be
>>> updated on migration or initialization. Not that it matters much in this
>>> case, but I wondered if there is something I'm missing.
>>>
>>
>> I would think the critical section is small enough that a spinlock makes
>> sense, but what I don't think we need is to add the additional lock.
>>
>> I think just taking the kvm->lock should be sufficient, which happens to
>> be a mutex, and while that may be a bit slower to take than the
>> spinlock, it's not in the critical path so let's just keep things
>> simple.
>>
>> Perhaps this what Marc also meant.
>
> That would be the logical conclusion, assuming that we can sleep on this
> path.
All right. I'll take kvm->lock there.
Thanks,
Jintack
>
> Thanks,
>
> M.
> --
> Jazz is not dead. It just smells funny...
>
Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On 30/01/17 14:45, Christoffer Dall wrote:
> On Sun, Jan 29, 2017 at 11:54:05AM +, Marc Zyngier wrote:
>> On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim
>> wrote:
>>> Make cntvoff per each timer context. This is helpful to abstract kvm
>>> timer functions to work with timer context without considering timer
>>> types (e.g. physical timer or virtual timer).
>>>
>>> This also would pave the way for ever doing adjustments of the cntvoff
>>> on a per-CPU basis if that should ever make sense.
>>>
>>> Signed-off-by: Jintack Lim
>>> ---
>>> arch/arm/include/asm/kvm_host.h | 6 +++---
>>> arch/arm64/include/asm/kvm_host.h | 4 ++--
>>> include/kvm/arm_arch_timer.h | 8 +++-
>>> virt/kvm/arm/arch_timer.c | 26 --
>>> virt/kvm/arm/hyp/timer-sr.c | 3 +--
>>> 5 files changed, 29 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/kvm_host.h
>>> b/arch/arm/include/asm/kvm_host.h
>>> index d5423ab..f5456a9 100644
>>> --- a/arch/arm/include/asm/kvm_host.h
>>> +++ b/arch/arm/include/asm/kvm_host.h
>>> @@ -60,9 +60,6 @@ struct kvm_arch {
>>> /* The last vcpu id that ran on each physical CPU */
>>> int __percpu *last_vcpu_ran;
>>>
>>> - /* Timer */
>>> - struct arch_timer_kvm timer;
>>> -
>>> /*
>>> * Anything that is not used directly from assembly code goes
>>> * here.
>>> @@ -75,6 +72,9 @@ struct kvm_arch {
>>> /* Stage-2 page table */
>>> pgd_t *pgd;
>>>
>>> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
>>> + spinlock_t cntvoff_lock;
>>
>> Is there any condition where we need this to be a spinlock? I would have
>> thought that a mutex should have been enough, as this should only be
>> updated on migration or initialization. Not that it matters much in this
>> case, but I wondered if there is something I'm missing.
>>
>
> I would think the critical section is small enough that a spinlock makes
> sense, but what I don't think we need is to add the additional lock.
>
> I think just taking the kvm->lock should be sufficient, which happens to
> be a mutex, and while that may be a bit slower to take than the
> spinlock, it's not in the critical path so let's just keep things
> simple.
>
> Perhaps this what Marc also meant.
That would be the logical conclusion, assuming that we can sleep on this
path.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On Sun, Jan 29, 2017 at 11:54:05AM +, Marc Zyngier wrote:
> On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim
> wrote:
> > Make cntvoff per each timer context. This is helpful to abstract kvm
> > timer functions to work with timer context without considering timer
> > types (e.g. physical timer or virtual timer).
> >
> > This also would pave the way for ever doing adjustments of the cntvoff
> > on a per-CPU basis if that should ever make sense.
> >
> > Signed-off-by: Jintack Lim
> > ---
> > arch/arm/include/asm/kvm_host.h | 6 +++---
> > arch/arm64/include/asm/kvm_host.h | 4 ++--
> > include/kvm/arm_arch_timer.h | 8 +++-
> > virt/kvm/arm/arch_timer.c | 26 --
> > virt/kvm/arm/hyp/timer-sr.c | 3 +--
> > 5 files changed, 29 insertions(+), 18 deletions(-)
> >
> > diff --git a/arch/arm/include/asm/kvm_host.h
> > b/arch/arm/include/asm/kvm_host.h
> > index d5423ab..f5456a9 100644
> > --- a/arch/arm/include/asm/kvm_host.h
> > +++ b/arch/arm/include/asm/kvm_host.h
> > @@ -60,9 +60,6 @@ struct kvm_arch {
> > /* The last vcpu id that ran on each physical CPU */
> > int __percpu *last_vcpu_ran;
> >
> > - /* Timer */
> > - struct arch_timer_kvm timer;
> > -
> > /*
> > * Anything that is not used directly from assembly code goes
> > * here.
> > @@ -75,6 +72,9 @@ struct kvm_arch {
> > /* Stage-2 page table */
> > pgd_t *pgd;
> >
> > + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
> > + spinlock_t cntvoff_lock;
>
> Is there any condition where we need this to be a spinlock? I would have
> thought that a mutex should have been enough, as this should only be
> updated on migration or initialization. Not that it matters much in this
> case, but I wondered if there is something I'm missing.
>
I would think the critical section is small enough that a spinlock makes
sense, but what I don't think we need is to add the additional lock.
I think just taking the kvm->lock should be sufficient, which happens to
be a mutex, and while that may be a bit slower to take than the
spinlock, it's not in the critical path so let's just keep things
simple.
Perhaps this what Marc also meant.
> > +
> > /* Interrupt controller */
> > struct vgic_distvgic;
> > int max_vcpus;
> > diff --git a/arch/arm64/include/asm/kvm_host.h
> > b/arch/arm64/include/asm/kvm_host.h
> > index e505038..23749a8 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -71,8 +71,8 @@ struct kvm_arch {
> > /* Interrupt controller */
> > struct vgic_distvgic;
> >
> > - /* Timer */
> > - struct arch_timer_kvm timer;
> > + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
> > + spinlock_t cntvoff_lock;
> > };
> >
> > #define KVM_NR_MEM_OBJS 40
> > diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> > index daad3c1..1b9c988 100644
> > --- a/include/kvm/arm_arch_timer.h
> > +++ b/include/kvm/arm_arch_timer.h
> > @@ -23,11 +23,6 @@
> > #include
> > #include
> >
> > -struct arch_timer_kvm {
> > - /* Virtual offset */
> > - u64 cntvoff;
> > -};
> > -
> > struct arch_timer_context {
> > /* Registers: control register, timer value */
> > u32 cnt_ctl;
> > @@ -38,6 +33,9 @@ struct arch_timer_context {
> >
> > /* Active IRQ state caching */
> > boolactive_cleared_last;
> > +
> > + /* Virtual offset */
> > + u64 cntvoff;
> > };
> >
> > struct arch_timer_cpu {
> > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> > index 6740efa..fa4c042 100644
> > --- a/virt/kvm/arm/arch_timer.c
> > +++ b/virt/kvm/arm/arch_timer.c
> > @@ -101,9 +101,10 @@ static void kvm_timer_inject_irq_work(struct
> > work_struct *work)
> > static u64 kvm_timer_compute_delta(struct kvm_vcpu *vcpu)
> > {
> > u64 cval, now;
> > + struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> >
> > - cval = vcpu_vtimer(vcpu)->cnt_cval;
> > - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
> > + cval = vtimer->cnt_cval;
> > + now = kvm_phys_timer_read() - vtimer->cntvoff;
> >
> > if (now < cval) {
> > u64 ns;
> > @@ -159,7 +160,7 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
> > return false;
> >
> > cval = vtimer->cnt_cval;
> > - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
> > + now = kvm_phys_timer_read() - vtimer->cntvoff;
> >
> > return cval <= now;
> > }
> > @@ -353,10 +354,23 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> > return 0;
> > }
> >
> > +/* Make the updates of cntvoff for all vtimer contexts atomic */
> > +static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
>
> Arguably, this acts on the VM itself and not a single vcpu. maybe you
> should consider p
Re: [RFC v2 02/10] KVM: arm/arm64: Move cntvoff to each timer context
On Fri, Jan 27 2017 at 01:04:52 AM, Jintack Lim wrote:
> Make cntvoff per each timer context. This is helpful to abstract kvm
> timer functions to work with timer context without considering timer
> types (e.g. physical timer or virtual timer).
>
> This also would pave the way for ever doing adjustments of the cntvoff
> on a per-CPU basis if that should ever make sense.
>
> Signed-off-by: Jintack Lim
> ---
> arch/arm/include/asm/kvm_host.h | 6 +++---
> arch/arm64/include/asm/kvm_host.h | 4 ++--
> include/kvm/arm_arch_timer.h | 8 +++-
> virt/kvm/arm/arch_timer.c | 26 --
> virt/kvm/arm/hyp/timer-sr.c | 3 +--
> 5 files changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index d5423ab..f5456a9 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -60,9 +60,6 @@ struct kvm_arch {
> /* The last vcpu id that ran on each physical CPU */
> int __percpu *last_vcpu_ran;
>
> - /* Timer */
> - struct arch_timer_kvm timer;
> -
> /*
>* Anything that is not used directly from assembly code goes
>* here.
> @@ -75,6 +72,9 @@ struct kvm_arch {
> /* Stage-2 page table */
> pgd_t *pgd;
>
> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
> + spinlock_t cntvoff_lock;
Is there any condition where we need this to be a spinlock? I would have
thought that a mutex should have been enough, as this should only be
updated on migration or initialization. Not that it matters much in this
case, but I wondered if there is something I'm missing.
> +
> /* Interrupt controller */
> struct vgic_distvgic;
> int max_vcpus;
> diff --git a/arch/arm64/include/asm/kvm_host.h
> b/arch/arm64/include/asm/kvm_host.h
> index e505038..23749a8 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -71,8 +71,8 @@ struct kvm_arch {
> /* Interrupt controller */
> struct vgic_distvgic;
>
> - /* Timer */
> - struct arch_timer_kvm timer;
> + /* A lock to synchronize cntvoff among all vtimer context of vcpus */
> + spinlock_t cntvoff_lock;
> };
>
> #define KVM_NR_MEM_OBJS 40
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index daad3c1..1b9c988 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -23,11 +23,6 @@
> #include
> #include
>
> -struct arch_timer_kvm {
> - /* Virtual offset */
> - u64 cntvoff;
> -};
> -
> struct arch_timer_context {
> /* Registers: control register, timer value */
> u32 cnt_ctl;
> @@ -38,6 +33,9 @@ struct arch_timer_context {
>
> /* Active IRQ state caching */
> boolactive_cleared_last;
> +
> + /* Virtual offset */
> + u64 cntvoff;
> };
>
> struct arch_timer_cpu {
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 6740efa..fa4c042 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -101,9 +101,10 @@ static void kvm_timer_inject_irq_work(struct work_struct
> *work)
> static u64 kvm_timer_compute_delta(struct kvm_vcpu *vcpu)
> {
> u64 cval, now;
> + struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>
> - cval = vcpu_vtimer(vcpu)->cnt_cval;
> - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
> + cval = vtimer->cnt_cval;
> + now = kvm_phys_timer_read() - vtimer->cntvoff;
>
> if (now < cval) {
> u64 ns;
> @@ -159,7 +160,7 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
> return false;
>
> cval = vtimer->cnt_cval;
> - now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
> + now = kvm_phys_timer_read() - vtimer->cntvoff;
>
> return cval <= now;
> }
> @@ -353,10 +354,23 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> return 0;
> }
>
> +/* Make the updates of cntvoff for all vtimer contexts atomic */
> +static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
Arguably, this acts on the VM itself and not a single vcpu. maybe you
should consider passing the struct kvm pointer to reflect this.
> +{
> + int i;
> +
> + spin_lock(&vcpu->kvm->arch.cntvoff_lock);
> + kvm_for_each_vcpu(i, vcpu, vcpu->kvm)
> + vcpu_vtimer(vcpu)->cntvoff = cntvoff;
> + spin_unlock(&vcpu->kvm->arch.cntvoff_lock);
> +}
> +
> void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
> {
> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>
> + update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
Maybe a comment indicating that we recompute CNTVOFF for all vcpus would
be welcome (this is not a change in semantics, but it was never obvious
in the existing c
