On Fri, Mar 24, 2023 at 02:46:57PM +0000, Marc Zyngier wrote: > Having the timer IRQs duplicated into each vcpu isn't great, and > becomes absolutely awful with NV. So let's move these into > the per-VM arch_timer_vm_data structure. > > This simplifies a lot of code, but requires us to introduce a > mutex so that we can reason about userspace trying to change > an interrupt number while another vcpu is running, something > that wasn't really well handled so far. > > Reviewed-by: Colton Lewis <coltonlewis@xxxxxxxxxx> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> > --- > arch/arm64/include/asm/kvm_host.h | 2 + > arch/arm64/kvm/arch_timer.c | 104 +++++++++++++++++------------- > arch/arm64/kvm/arm.c | 2 + > include/kvm/arm_arch_timer.h | 18 ++++-- > 4 files changed, 78 insertions(+), 48 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 116233a390e9..1280154c9ef3 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -223,6 +223,8 @@ struct kvm_arch { > #define KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED 5 > /* VM counter offset */ > #define KVM_ARCH_FLAG_VM_COUNTER_OFFSET 6 > + /* Timer PPIs made immutable */ > +#define KVM_ARCH_FLAG_TIMER_PPIS_IMMUTABLE 7 > > unsigned long flags; > > diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c > index 7cd0b0947454..88a38d45d352 100644 > --- a/arch/arm64/kvm/arch_timer.c > +++ b/arch/arm64/kvm/arch_timer.c > @@ -851,7 +851,6 @@ static void timer_context_init(struct kvm_vcpu *vcpu, int timerid) > > hrtimer_init(&ctxt->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); > ctxt->hrtimer.function = kvm_hrtimer_expire; > - timer_irq(ctxt) = default_ppi[timerid]; > > switch (timerid) { > case TIMER_PTIMER: > @@ -880,6 +879,13 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) > timer->bg_timer.function = kvm_bg_timer_expire; > } > > +void kvm_timer_init_vm(struct kvm *kvm) > +{ > + mutex_init(&kvm->arch.timer_data.lock); > + for (int i = 0; i < NR_KVM_TIMERS; i++) > + kvm->arch.timer_data.ppi[i] = default_ppi[i]; > +} > + > void kvm_timer_cpu_up(void) > { > enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags); > @@ -1292,44 +1298,52 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu) > > static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu) > { > - int vtimer_irq, ptimer_irq, ret; > - unsigned long i; > + u32 ppis = 0; > > - vtimer_irq = timer_irq(vcpu_vtimer(vcpu)); > - ret = kvm_vgic_set_owner(vcpu, vtimer_irq, vcpu_vtimer(vcpu)); > - if (ret) > - return false; > + mutex_lock(&vcpu->kvm->arch.timer_data.lock); > > - ptimer_irq = timer_irq(vcpu_ptimer(vcpu)); > - ret = kvm_vgic_set_owner(vcpu, ptimer_irq, vcpu_ptimer(vcpu)); > - if (ret) > - return false; > + for (int i = 0; i < NR_KVM_TIMERS; i++) { > + struct arch_timer_context *ctx; > + int irq; > > - kvm_for_each_vcpu(i, vcpu, vcpu->kvm) { > - if (timer_irq(vcpu_vtimer(vcpu)) != vtimer_irq || > - timer_irq(vcpu_ptimer(vcpu)) != ptimer_irq) > - return false; > + ctx = vcpu_get_timer(vcpu, i); > + irq = timer_irq(ctx); > + if (kvm_vgic_set_owner(vcpu, irq, ctx)) > + break; > + > + /* > + * We know by construction that we only have PPIs, so > + * all values are less than 32. > + */ > + ppis |= BIT(irq); > } > > - return true; > + set_bit(KVM_ARCH_FLAG_TIMER_PPIS_IMMUTABLE, &vcpu->kvm->arch.flags); > + > + mutex_unlock(&vcpu->kvm->arch.timer_data.lock); > + > + return hweight32(ppis) == NR_KVM_TIMERS; Does it make sense to only set the IMMUTABLE flag if the timer IRQs are indeed valid? I doubt userspace would do anything when it gets the EINVAL, but it is possible userspace could make another attempt at configuring the IRQs correctly. I believe that was the existing behavior of the UAPI. -- Thanks, Oliver