From mboxrd@z Thu Jan 1 00:00:00 1970 From: tn@semihalf.com (Tomasz Nowicki) Date: Wed, 31 Jan 2018 09:32:33 +0100 Subject: [PATCH v9 7/9] KVM: arm/arm64: Provide a get_input_level for the arch timer In-Reply-To: <20180130124947.GX21802@cbox> References: <20171220113606.7030-1-christoffer.dall@linaro.org> <20171220113606.7030-8-christoffer.dall@linaro.org> <20180130124947.GX21802@cbox> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Christoffer, On 30.01.2018 13:49, Christoffer Dall wrote: > Hi Tomasz, > > On Mon, Jan 22, 2018 at 01:32:57PM +0100, Tomasz Nowicki wrote: >> On 20.12.2017 12:36, Christoffer Dall wrote: >>> The VGIC can now support the life-cycle of mapped level-triggered >>> interrupts, and we no longer have to read back the timer state on every >>> exit from the VM if we had an asserted timer interrupt signal, because >>> the VGIC already knows if we hit the unlikely case where the guest >>> disables the timer without ACKing the virtual timer interrupt. >>> >>> This means we rework a bit of the code to factor out the functionality >>> to snapshot the timer state from vtimer_save_state(), and we can reuse >>> this functionality in the sync path when we have an irqchip in >>> userspace, and also to support our implementation of the >>> get_input_level() function for the timer. >>> >>> This change also means that we can no longer rely on the timer's view of >>> the interrupt line to set the active state, because we no longer >>> maintain this state for mapped interrupts when exiting from the guest. >>> Instead, we only set the active state if the virtual interrupt is >>> active, and otherwise we simply let the timer fire again and raise the >>> virtual interrupt from the ISR. >>> >>> Reviewed-by: Eric Auger >>> Reviewed-by: Marc Zyngier >>> Signed-off-by: Christoffer Dall >>> --- >>> include/kvm/arm_arch_timer.h | 2 ++ >>> virt/kvm/arm/arch_timer.c | 84 ++++++++++++++++++++------------------------ >>> 2 files changed, 40 insertions(+), 46 deletions(-) >>> >>> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h >>> index 6e45608b2399..b1dcfde0a3ef 100644 >>> --- a/include/kvm/arm_arch_timer.h >>> +++ b/include/kvm/arm_arch_timer.h >>> @@ -90,6 +90,8 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu); >>> void kvm_timer_init_vhe(void); >>> +bool kvm_arch_timer_get_input_level(int vintid); >>> + >>> #define vcpu_vtimer(v) (&(v)->arch.timer_cpu.vtimer) >>> #define vcpu_ptimer(v) (&(v)->arch.timer_cpu.ptimer) >>> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c >>> index fb0533ed903d..d845d67b7062 100644 >>> --- a/virt/kvm/arm/arch_timer.c >>> +++ b/virt/kvm/arm/arch_timer.c >>> @@ -343,6 +343,12 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu) >>> phys_timer_emulate(vcpu); >>> } >>> +static void __timer_snapshot_state(struct arch_timer_context *timer) >>> +{ >>> + timer->cnt_ctl = read_sysreg_el0(cntv_ctl); >>> + timer->cnt_cval = read_sysreg_el0(cntv_cval); >>> +} >>> + >>> static void vtimer_save_state(struct kvm_vcpu *vcpu) >>> { >>> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; >>> @@ -354,10 +360,8 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu) >>> if (!vtimer->loaded) >>> goto out; >>> - if (timer->enabled) { >>> - vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl); >>> - vtimer->cnt_cval = read_sysreg_el0(cntv_cval); >>> - } >>> + if (timer->enabled) >>> + __timer_snapshot_state(vtimer); >>> /* Disable the virtual timer */ >>> write_sysreg_el0(0, cntv_ctl); >>> @@ -454,8 +458,7 @@ static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu) >>> bool phys_active; >>> int ret; >>> - phys_active = vtimer->irq.level || >>> - kvm_vgic_map_is_active(vcpu, vtimer->irq.irq); >>> + phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq); >>> ret = irq_set_irqchip_state(host_vtimer_irq, >>> IRQCHIP_STATE_ACTIVE, >>> @@ -535,54 +538,27 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu) >>> set_cntvoff(0); >>> } >>> -static void unmask_vtimer_irq(struct kvm_vcpu *vcpu) >>> +/* >>> + * With a userspace irqchip we have to check if the guest de-asserted the >>> + * timer and if so, unmask the timer irq signal on the host interrupt >>> + * controller to ensure that we see future timer signals. >>> + */ >>> +static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu) >>> { >>> struct arch_timer_context *vtimer = vcpu_vtimer(vcpu); >>> if (unlikely(!irqchip_in_kernel(vcpu->kvm))) { >>> - kvm_vtimer_update_mask_user(vcpu); >>> - return; >>> - } >>> - >>> - /* >>> - * If the guest disabled the timer without acking the interrupt, then >>> - * we must make sure the physical and virtual active states are in >>> - * sync by deactivating the physical interrupt, because otherwise we >>> - * wouldn't see the next timer interrupt in the host. >>> - */ >>> - if (!kvm_vgic_map_is_active(vcpu, vtimer->irq.irq)) { >>> - int ret; >>> - ret = irq_set_irqchip_state(host_vtimer_irq, >>> - IRQCHIP_STATE_ACTIVE, >>> - false); >>> - WARN_ON(ret); >>> + __timer_snapshot_state(vtimer); >>> + if (!kvm_timer_should_fire(vtimer)) { >>> + kvm_timer_update_irq(vcpu, false, vtimer); >>> + kvm_vtimer_update_mask_user(vcpu); >>> + } >>> } >>> } >>> -/** >>> - * kvm_timer_sync_hwstate - sync timer state from cpu >>> - * @vcpu: The vcpu pointer >>> - * >>> - * Check if any of the timers have expired while we were running in the guest, >>> - * and inject an interrupt if that was the case. >>> - */ >>> void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu) >>> { >>> - struct arch_timer_context *vtimer = vcpu_vtimer(vcpu); >>> - >>> - /* >>> - * If we entered the guest with the vtimer output asserted we have to >>> - * check if the guest has modified the timer so that we should lower >>> - * the line at this point. >>> - */ >>> - if (vtimer->irq.level) { >>> - vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl); >>> - vtimer->cnt_cval = read_sysreg_el0(cntv_cval); >>> - if (!kvm_timer_should_fire(vtimer)) { >>> - kvm_timer_update_irq(vcpu, false, vtimer); >>> - unmask_vtimer_irq(vcpu); >>> - } >>> - } >>> + unmask_vtimer_irq_user(vcpu); >>> } >> >> While testing your VHE optimization series [1] I noticed massive WFI exits >> on ThunderX2 so I bisected 'vhe-optimize-v3-with-fixes' branch of [2] down >> to this commit. >> >> The host traps on WFI so that VCPU thread should be scheduled out for some >> time. However, this is not happening because kvm_vcpu_block() -> >> kvm_vcpu_check_block() gives negative value (vtimer->irq.level is asserted) >> and VCPU is woken up immediately. Nobody takes care about lowering the >> vtimer line in this case. >> >> I reverted shape of above kvm_timer_sync_hwstate() and things are good now. >> Before I start digging I wanted to check with you. Can you please check on >> your side? >> > > This patch should fix the issue, thanks for pointing it out. > https://lists.cs.columbia.edu/pipermail/kvmarm/2018-January/029582.html > > I'd be happy to hear if you can confirm this or not. Yes, the issue is fixed. Thanks! > > I forgot that my git auto-cc doesn't pick up reported-by tags (I should > fix that), so apologies for not cc'ing you on the series. > No problem at all. Tomasz