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Fri, 17 Apr 2026 15:56:35 +0000 Date: Fri, 17 Apr 2026 16:56:35 +0100 Message-ID: <86tst91sy4.wl-maz@kernel.org> From: Marc Zyngier To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: Deepanshu Kartikey , Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu Subject: Re: [PATCH 2/4] KVM: arm64: timer: Kill the per-timer level cache In-Reply-To: <20260417124612.2770268-3-maz@kernel.org> References: <20260417124612.2770268-1-maz@kernel.org> <20260417124612.2770268-3-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kartikey406@gmail.com, joey.gouly@arm.com, suzuki.poulose@arm.com, oupton@kernel.org, yuzenghui@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 17 Apr 2026 13:46:10 +0100, Marc Zyngier wrote: > > The timer code makes use of a per-timer irq level cache, which > looks like a very minor optimisation to avoid taking a lock upon > updating the GIC view of the interrupt when it is unchanged from > the previous state. > > This is coming in the way of more important correctness issues, > so get rid of the cache, which simplifies a couple of minor things. > > Signed-off-by: Marc Zyngier > --- > arch/arm64/kvm/arch_timer.c | 18 +++++++++--------- > include/kvm/arm_arch_timer.h | 5 ----- > 2 files changed, 9 insertions(+), 14 deletions(-) > > diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c > index d6802fc87e085..fdc1afff06340 100644 > --- a/arch/arm64/kvm/arch_timer.c > +++ b/arch/arm64/kvm/arch_timer.c > @@ -446,9 +446,8 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, > { > kvm_timer_update_status(timer_ctx, new_level); > > - timer_ctx->irq.level = new_level; > trace_kvm_timer_update_irq(vcpu->vcpu_id, timer_irq(timer_ctx), > - timer_ctx->irq.level); > + new_level); > > if (userspace_irqchip(vcpu->kvm)) > return; > @@ -466,7 +465,7 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, > > kvm_vgic_inject_irq(vcpu->kvm, vcpu, > timer_irq(timer_ctx), > - timer_ctx->irq.level, > + new_level, > timer_ctx); > } > > @@ -477,8 +476,7 @@ static void timer_emulate(struct arch_timer_context *ctx) > > trace_kvm_timer_emulate(ctx, pending); > > - if (pending != ctx->irq.level) > - kvm_timer_update_irq(timer_context_to_vcpu(ctx), pending, ctx); > + kvm_timer_update_irq(timer_context_to_vcpu(ctx), pending, ctx); > > kvm_timer_update_status(ctx, pending); As my new best mate Sashiko pointed out, kvm_timer_update_status() here becomes redundant, as the unconditional call to kvm_timer_update_irq() already contains that. I'll drop it from the patch when applying, unless there are more comments. Thanks, M. -- Without deviation from the norm, progress is not possible.