* [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value
@ 2023-02-24 19:16 Marc Zyngier
2023-02-28 11:26 ` Joey Gouly
2023-03-11 21:36 ` Oliver Upton
0 siblings, 2 replies; 5+ messages in thread
From: Marc Zyngier @ 2023-02-24 19:16 UTC (permalink / raw)
To: kvmarm, linux-arm-kernel, kvm
Cc: James Morse, Suzuki K Poulose, Oliver Upton, Zenghui Yu,
Joey Gouly, Reiji Watanabe
Having a per-vcpu virtual offset is a pain. It needs to be synchronized
on each update, and expands badly to a setup where different timers can
have different offsets, or have composite offsets (as with NV).
So let's start by replacing the use of the CNTVOFF_EL2 shadow register
(which we want to reclaim for NV anyway), and make the virtual timer
carry a pointer to a VM-wide offset.
This simplifies the code significantly. It also addresses two terrible bugs:
- The use of CNTVOFF_EL2 leads to some nice offset corruption
when the sysreg gets reset, as reported by Joey.
- The kvm mutex is taken from a vcpu ioctl, which goes against
the locking rules...
Reported-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230224173915.GA17407@e124191.cambridge.arm.com
---
arch/arm64/include/asm/kvm_host.h | 3 +++
arch/arm64/kvm/arch_timer.c | 45 +++++++------------------------
arch/arm64/kvm/hypercalls.c | 2 +-
include/kvm/arm_arch_timer.h | 15 +++++++++++
4 files changed, 29 insertions(+), 36 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a1892a8f6032..bcd774d74f34 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -193,6 +193,9 @@ struct kvm_arch {
/* Interrupt controller */
struct vgic_dist vgic;
+ /* Timers */
+ struct arch_timer_vm_data timer_data;
+
/* Mandated version of PSCI */
u32 psci_version;
diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 00610477ec7b..e1af4301b913 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -84,14 +84,10 @@ u64 timer_get_cval(struct arch_timer_context *ctxt)
static u64 timer_get_offset(struct arch_timer_context *ctxt)
{
- struct kvm_vcpu *vcpu = ctxt->vcpu;
+ if (ctxt->offset.vm_offset)
+ return *ctxt->offset.vm_offset;
- switch(arch_timer_ctx_index(ctxt)) {
- case TIMER_VTIMER:
- return __vcpu_sys_reg(vcpu, CNTVOFF_EL2);
- default:
- return 0;
- }
+ return 0;
}
static void timer_set_ctl(struct arch_timer_context *ctxt, u32 ctl)
@@ -128,15 +124,12 @@ static void timer_set_cval(struct arch_timer_context *ctxt, u64 cval)
static void timer_set_offset(struct arch_timer_context *ctxt, u64 offset)
{
- struct kvm_vcpu *vcpu = ctxt->vcpu;
-
- switch(arch_timer_ctx_index(ctxt)) {
- case TIMER_VTIMER:
- __vcpu_sys_reg(vcpu, CNTVOFF_EL2) = offset;
- break;
- default:
+ if (!ctxt->offset.vm_offset) {
WARN(offset, "timer %ld\n", arch_timer_ctx_index(ctxt));
+ return;
}
+
+ WRITE_ONCE(*ctxt->offset.vm_offset, offset);
}
u64 kvm_phys_timer_read(void)
@@ -765,25 +758,6 @@ 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)
-{
- unsigned long i;
- struct kvm *kvm = vcpu->kvm;
- struct kvm_vcpu *tmp;
-
- mutex_lock(&kvm->lock);
- kvm_for_each_vcpu(i, tmp, kvm)
- timer_set_offset(vcpu_vtimer(tmp), cntvoff);
-
- /*
- * When called from the vcpu create path, the CPU being created is not
- * included in the loop above, so we just set it here as well.
- */
- timer_set_offset(vcpu_vtimer(vcpu), cntvoff);
- mutex_unlock(&kvm->lock);
-}
-
void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
{
struct arch_timer_cpu *timer = vcpu_timer(vcpu);
@@ -791,10 +765,11 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
vtimer->vcpu = vcpu;
+ vtimer->offset.vm_offset = &vcpu->kvm->arch.timer_data.voffset;
ptimer->vcpu = vcpu;
/* Synchronize cntvoff across all vtimers of a VM. */
- update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
+ timer_set_offset(vtimer, kvm_phys_timer_read());
timer_set_offset(ptimer, 0);
hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
@@ -840,7 +815,7 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
break;
case KVM_REG_ARM_TIMER_CNT:
timer = vcpu_vtimer(vcpu);
- update_vtimer_cntvoff(vcpu, kvm_phys_timer_read() - value);
+ timer_set_offset(timer, kvm_phys_timer_read() - value);
break;
case KVM_REG_ARM_TIMER_CVAL:
timer = vcpu_vtimer(vcpu);
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 64c086c02c60..5da884e11337 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -44,7 +44,7 @@ static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
feature = smccc_get_arg1(vcpu);
switch (feature) {
case KVM_PTP_VIRT_COUNTER:
- cycles = systime_snapshot.cycles - vcpu_read_sys_reg(vcpu, CNTVOFF_EL2);
+ cycles = systime_snapshot.cycles - vcpu->kvm->arch.timer_data.voffset;
break;
case KVM_PTP_PHYS_COUNTER:
cycles = systime_snapshot.cycles;
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index 71916de7c6c4..c52a6e6839da 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -23,6 +23,19 @@ enum kvm_arch_timer_regs {
TIMER_REG_CTL,
};
+struct arch_timer_offset {
+ /*
+ * If set, pointer to one of the offsets in the kvm's offset
+ * structure. If NULL, assume a zero offset.
+ */
+ u64 *vm_offset;
+};
+
+struct arch_timer_vm_data {
+ /* Offset applied to the virtual timer/counter */
+ u64 voffset;
+};
+
struct arch_timer_context {
struct kvm_vcpu *vcpu;
@@ -32,6 +45,8 @@ struct arch_timer_context {
/* Emulated Timer (may be unused) */
struct hrtimer hrtimer;
+ /* Offset for this counter/timer */
+ struct arch_timer_offset offset;
/*
* We have multiple paths which can save/restore the timer state onto
* the hardware, so we need some way of keeping track of where the
--
2.34.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value
2023-02-24 19:16 [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value Marc Zyngier
@ 2023-02-28 11:26 ` Joey Gouly
2023-02-28 19:18 ` Marc Zyngier
2023-03-11 21:36 ` Oliver Upton
1 sibling, 1 reply; 5+ messages in thread
From: Joey Gouly @ 2023-02-28 11:26 UTC (permalink / raw)
To: Marc Zyngier
Cc: kvmarm, linux-arm-kernel, kvm, James Morse, Suzuki K Poulose,
Oliver Upton, Zenghui Yu, Reiji Watanabe, nd
Hi Marc,
On Fri, Feb 24, 2023 at 07:16:40PM +0000, Marc Zyngier wrote:
> Having a per-vcpu virtual offset is a pain. It needs to be synchronized
> on each update, and expands badly to a setup where different timers can
> have different offsets, or have composite offsets (as with NV).
>
> So let's start by replacing the use of the CNTVOFF_EL2 shadow register
> (which we want to reclaim for NV anyway), and make the virtual timer
> carry a pointer to a VM-wide offset.
>
> This simplifies the code significantly. It also addresses two terrible bugs:
>
> - The use of CNTVOFF_EL2 leads to some nice offset corruption
> when the sysreg gets reset, as reported by Joey.
>
> - The kvm mutex is taken from a vcpu ioctl, which goes against
> the locking rules...
>
> Reported-by: Joey Gouly <joey.gouly@arm.com>
> Reviewed-by: Reiji Watanabe <reijiw@google.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Link: https://lore.kernel.org/r/20230224173915.GA17407@e124191.cambridge.arm.com
Fixes my mismatched timer offset issues.
Tested-by: Joey Gouly <joey.gouly@arm.com>
Thanks,
Joey
> ---
> arch/arm64/include/asm/kvm_host.h | 3 +++
> arch/arm64/kvm/arch_timer.c | 45 +++++++------------------------
> arch/arm64/kvm/hypercalls.c | 2 +-
> include/kvm/arm_arch_timer.h | 15 +++++++++++
> 4 files changed, 29 insertions(+), 36 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index a1892a8f6032..bcd774d74f34 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -193,6 +193,9 @@ struct kvm_arch {
> /* Interrupt controller */
> struct vgic_dist vgic;
>
> + /* Timers */
> + struct arch_timer_vm_data timer_data;
> +
> /* Mandated version of PSCI */
> u32 psci_version;
>
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index 00610477ec7b..e1af4301b913 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -84,14 +84,10 @@ u64 timer_get_cval(struct arch_timer_context *ctxt)
>
> static u64 timer_get_offset(struct arch_timer_context *ctxt)
> {
> - struct kvm_vcpu *vcpu = ctxt->vcpu;
> + if (ctxt->offset.vm_offset)
> + return *ctxt->offset.vm_offset;
>
> - switch(arch_timer_ctx_index(ctxt)) {
> - case TIMER_VTIMER:
> - return __vcpu_sys_reg(vcpu, CNTVOFF_EL2);
> - default:
> - return 0;
> - }
> + return 0;
> }
>
> static void timer_set_ctl(struct arch_timer_context *ctxt, u32 ctl)
> @@ -128,15 +124,12 @@ static void timer_set_cval(struct arch_timer_context *ctxt, u64 cval)
>
> static void timer_set_offset(struct arch_timer_context *ctxt, u64 offset)
> {
> - struct kvm_vcpu *vcpu = ctxt->vcpu;
> -
> - switch(arch_timer_ctx_index(ctxt)) {
> - case TIMER_VTIMER:
> - __vcpu_sys_reg(vcpu, CNTVOFF_EL2) = offset;
> - break;
> - default:
> + if (!ctxt->offset.vm_offset) {
> WARN(offset, "timer %ld\n", arch_timer_ctx_index(ctxt));
> + return;
> }
> +
> + WRITE_ONCE(*ctxt->offset.vm_offset, offset);
> }
>
> u64 kvm_phys_timer_read(void)
> @@ -765,25 +758,6 @@ 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)
> -{
> - unsigned long i;
> - struct kvm *kvm = vcpu->kvm;
> - struct kvm_vcpu *tmp;
> -
> - mutex_lock(&kvm->lock);
> - kvm_for_each_vcpu(i, tmp, kvm)
> - timer_set_offset(vcpu_vtimer(tmp), cntvoff);
> -
> - /*
> - * When called from the vcpu create path, the CPU being created is not
> - * included in the loop above, so we just set it here as well.
> - */
> - timer_set_offset(vcpu_vtimer(vcpu), cntvoff);
> - mutex_unlock(&kvm->lock);
> -}
> -
> void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
> {
> struct arch_timer_cpu *timer = vcpu_timer(vcpu);
> @@ -791,10 +765,11 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
> struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
>
> vtimer->vcpu = vcpu;
> + vtimer->offset.vm_offset = &vcpu->kvm->arch.timer_data.voffset;
> ptimer->vcpu = vcpu;
>
> /* Synchronize cntvoff across all vtimers of a VM. */
> - update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
> + timer_set_offset(vtimer, kvm_phys_timer_read());
> timer_set_offset(ptimer, 0);
>
> hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
> @@ -840,7 +815,7 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
> break;
> case KVM_REG_ARM_TIMER_CNT:
> timer = vcpu_vtimer(vcpu);
> - update_vtimer_cntvoff(vcpu, kvm_phys_timer_read() - value);
> + timer_set_offset(timer, kvm_phys_timer_read() - value);
> break;
> case KVM_REG_ARM_TIMER_CVAL:
> timer = vcpu_vtimer(vcpu);
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 64c086c02c60..5da884e11337 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -44,7 +44,7 @@ static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
> feature = smccc_get_arg1(vcpu);
> switch (feature) {
> case KVM_PTP_VIRT_COUNTER:
> - cycles = systime_snapshot.cycles - vcpu_read_sys_reg(vcpu, CNTVOFF_EL2);
> + cycles = systime_snapshot.cycles - vcpu->kvm->arch.timer_data.voffset;
> break;
> case KVM_PTP_PHYS_COUNTER:
> cycles = systime_snapshot.cycles;
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index 71916de7c6c4..c52a6e6839da 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -23,6 +23,19 @@ enum kvm_arch_timer_regs {
> TIMER_REG_CTL,
> };
>
> +struct arch_timer_offset {
> + /*
> + * If set, pointer to one of the offsets in the kvm's offset
> + * structure. If NULL, assume a zero offset.
> + */
> + u64 *vm_offset;
> +};
> +
> +struct arch_timer_vm_data {
> + /* Offset applied to the virtual timer/counter */
> + u64 voffset;
> +};
> +
> struct arch_timer_context {
> struct kvm_vcpu *vcpu;
>
> @@ -32,6 +45,8 @@ struct arch_timer_context {
> /* Emulated Timer (may be unused) */
> struct hrtimer hrtimer;
>
> + /* Offset for this counter/timer */
> + struct arch_timer_offset offset;
> /*
> * We have multiple paths which can save/restore the timer state onto
> * the hardware, so we need some way of keeping track of where the
> --
> 2.34.1
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value
2023-02-28 11:26 ` Joey Gouly
@ 2023-02-28 19:18 ` Marc Zyngier
2023-02-28 19:22 ` Oliver Upton
0 siblings, 1 reply; 5+ messages in thread
From: Marc Zyngier @ 2023-02-28 19:18 UTC (permalink / raw)
To: Joey Gouly
Cc: kvmarm, linux-arm-kernel, kvm, James Morse, Suzuki K Poulose,
Oliver Upton, Zenghui Yu, Reiji Watanabe, nd
On Tue, 28 Feb 2023 11:26:07 +0000,
Joey Gouly <joey.gouly@arm.com> wrote:
>
> Hi Marc,
>
> On Fri, Feb 24, 2023 at 07:16:40PM +0000, Marc Zyngier wrote:
> > Having a per-vcpu virtual offset is a pain. It needs to be synchronized
> > on each update, and expands badly to a setup where different timers can
> > have different offsets, or have composite offsets (as with NV).
> >
> > So let's start by replacing the use of the CNTVOFF_EL2 shadow register
> > (which we want to reclaim for NV anyway), and make the virtual timer
> > carry a pointer to a VM-wide offset.
> >
> > This simplifies the code significantly. It also addresses two terrible bugs:
> >
> > - The use of CNTVOFF_EL2 leads to some nice offset corruption
> > when the sysreg gets reset, as reported by Joey.
> >
> > - The kvm mutex is taken from a vcpu ioctl, which goes against
> > the locking rules...
> >
> > Reported-by: Joey Gouly <joey.gouly@arm.com>
> > Reviewed-by: Reiji Watanabe <reijiw@google.com>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Link: https://lore.kernel.org/r/20230224173915.GA17407@e124191.cambridge.arm.com
>
> Fixes my mismatched timer offset issues.
>
> Tested-by: Joey Gouly <joey.gouly@arm.com>
Thanks for having given it a go. Hopefully Oliver will be able to send
this to as a fix shortly.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value
2023-02-28 19:18 ` Marc Zyngier
@ 2023-02-28 19:22 ` Oliver Upton
0 siblings, 0 replies; 5+ messages in thread
From: Oliver Upton @ 2023-02-28 19:22 UTC (permalink / raw)
To: Marc Zyngier
Cc: Joey Gouly, kvmarm, linux-arm-kernel, kvm, James Morse,
Suzuki K Poulose, Zenghui Yu, Reiji Watanabe, nd
On Tue, Feb 28, 2023 at 07:18:38PM +0000, Marc Zyngier wrote:
> On Tue, 28 Feb 2023 11:26:07 +0000,
> Joey Gouly <joey.gouly@arm.com> wrote:
> >
> > Hi Marc,
> >
> > On Fri, Feb 24, 2023 at 07:16:40PM +0000, Marc Zyngier wrote:
> > > Having a per-vcpu virtual offset is a pain. It needs to be synchronized
> > > on each update, and expands badly to a setup where different timers can
> > > have different offsets, or have composite offsets (as with NV).
> > >
> > > So let's start by replacing the use of the CNTVOFF_EL2 shadow register
> > > (which we want to reclaim for NV anyway), and make the virtual timer
> > > carry a pointer to a VM-wide offset.
> > >
> > > This simplifies the code significantly. It also addresses two terrible bugs:
> > >
> > > - The use of CNTVOFF_EL2 leads to some nice offset corruption
> > > when the sysreg gets reset, as reported by Joey.
> > >
> > > - The kvm mutex is taken from a vcpu ioctl, which goes against
> > > the locking rules...
> > >
> > > Reported-by: Joey Gouly <joey.gouly@arm.com>
> > > Reviewed-by: Reiji Watanabe <reijiw@google.com>
> > > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > > Link: https://lore.kernel.org/r/20230224173915.GA17407@e124191.cambridge.arm.com
> >
> > Fixes my mismatched timer offset issues.
> >
> > Tested-by: Joey Gouly <joey.gouly@arm.com>
>
> Thanks for having given it a go. Hopefully Oliver will be able to send
> this to as a fix shortly.
Absolutely, I have this queued up. Thanks for testing the patch Joey.
Want to see if I can get push access to the kvmarm repository in time,
otherwise I'll send a pull to you Marc.
--
Thanks,
Oliver
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value
2023-02-24 19:16 [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value Marc Zyngier
2023-02-28 11:26 ` Joey Gouly
@ 2023-03-11 21:36 ` Oliver Upton
1 sibling, 0 replies; 5+ messages in thread
From: Oliver Upton @ 2023-03-11 21:36 UTC (permalink / raw)
To: kvmarm, kvm, Marc Zyngier, linux-arm-kernel
Cc: Oliver Upton, Suzuki K Poulose, Zenghui Yu, James Morse,
Joey Gouly, Reiji Watanabe
On Fri, 24 Feb 2023 19:16:40 +0000, Marc Zyngier wrote:
> Having a per-vcpu virtual offset is a pain. It needs to be synchronized
> on each update, and expands badly to a setup where different timers can
> have different offsets, or have composite offsets (as with NV).
>
> So let's start by replacing the use of the CNTVOFF_EL2 shadow register
> (which we want to reclaim for NV anyway), and make the virtual timer
> carry a pointer to a VM-wide offset.
>
> [...]
Applied to kvmarm/fixes, thanks!
[1/1] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value
https://git.kernel.org/kvmarm/kvmarm/c/47053904e182
--
Best,
Oliver
^ permalink raw reply [flat|nested] 5+ messages in thread
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2023-02-24 19:16 [PATCH v2] KVM: arm64: timers: Convert per-vcpu virtual offset to a global value Marc Zyngier
2023-02-28 11:26 ` Joey Gouly
2023-02-28 19:18 ` Marc Zyngier
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