From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 65C5FD6554E for ; Wed, 17 Dec 2025 11:49:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=wga2G7vEvUnhQvXk0fzzJEMJ+JzaQfo7Zev7g481zco=; b=bBYQALXMIKTuU/C/BYcs8kOC+j ZIw135sHqJYYSrrl3oP5loaQQykekHVtV4uGZIaRW3FCymRJ/f5kJW/7uAIrqSiKCRzOuLfjvt/4V QtMGrgls7dG00tyQqdnfE0s9ePACabvV+qPc+Xc+YrVmf/cn4UhyYfsoN4IIjQPYmD2kPbZ92KvgO FaZuAJaWp1HrWOp9bXydC6hMbx2ho4f0suSqPRLBU4Fgr+xi8mPZLdvKSI6F3+2g4w2JhBmSannrW A5CwTRkAX4ONT8AFnE5DZj1rz1VPfxmlQG4F0nscXlL1EpZGeS70gOyLL1a5hS7lY+67OG32MxX+Y isBftS5A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vVq2L-00000006ka6-3zZt; Wed, 17 Dec 2025 11:49:45 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vVq2I-00000006kZZ-3eFt for linux-arm-kernel@lists.infradead.org; Wed, 17 Dec 2025 11:49:44 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9E56514BF; Wed, 17 Dec 2025 03:49:32 -0800 (PST) Received: from e124191.cambridge.arm.com (e124191.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BC8CF3F73B; Wed, 17 Dec 2025 03:49:37 -0800 (PST) Date: Wed, 17 Dec 2025 11:49:32 +0000 From: Joey Gouly To: Sascha Bischoff Cc: "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "kvm@vger.kernel.org" , nd , "maz@kernel.org" , "oliver.upton@linux.dev" , Suzuki Poulose , "yuzenghui@huawei.com" , "peter.maydell@linaro.org" , "lpieralisi@kernel.org" , Timothy Hayes Subject: Re: [PATCH 18/32] KVM: arm64: gic-v5: Check for pending PPIs Message-ID: <20251217114932.GA1626516@e124191.cambridge.arm.com> References: <20251212152215.675767-1-sascha.bischoff@arm.com> <20251212152215.675767-19-sascha.bischoff@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251212152215.675767-19-sascha.bischoff@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251217_034943_019334_EA5F91C0 X-CRM114-Status: GOOD ( 34.80 ) 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 Hi Sascha, On Fri, Dec 12, 2025 at 03:22:41PM +0000, Sascha Bischoff wrote: > This change allows KVM to check for pending PPI interrupts. This has > two main components: > > First of all, the effective priority mask is calculated. This is a > combination of the priority mask in the VPEs ICC_PCR_EL1.PRIORITY and > the currently running priority as determined from the VPE's > ICH_APR_EL1. If an interrupt's prioirity is greater than or equal to > the effective priority mask, it can be signalled. Otherwise, it > cannot. > > Secondly, any Enabled and Pending PPIs must be checked against this > compound priority mask. The reqires the PPI priorities to by synced > back to the KVM shadow state - this is skipped in general operation as > it isn't required and is rather expensive. If any Enabled and Pending > PPIs are of sufficient priority to be signalled, then there are > pending PPIs. Else, there are not. This ensures that a VPE is not > woken when it cannot actually process the pending interrupts. > > Signed-off-by: Sascha Bischoff > --- > arch/arm64/kvm/vgic/vgic-v5.c | 123 ++++++++++++++++++++++++++++++++++ > arch/arm64/kvm/vgic/vgic.c | 10 ++- > arch/arm64/kvm/vgic/vgic.h | 1 + > 3 files changed, 131 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/vgic/vgic-v5.c b/arch/arm64/kvm/vgic/vgic-v5.c > index d54595fbf4586..35740e88b3591 100644 > --- a/arch/arm64/kvm/vgic/vgic-v5.c > +++ b/arch/arm64/kvm/vgic/vgic-v5.c > @@ -54,6 +54,31 @@ int vgic_v5_probe(const struct gic_kvm_info *info) > return 0; > } > > +static u32 vgic_v5_get_effective_priority_mask(struct kvm_vcpu *vcpu) > +{ > + struct vgic_v5_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v5; > + unsigned highest_ap, priority_mask; > + > + /* > + * Counting the number of trailing zeros gives the current > + * active priority. Explicitly use the 32-bit version here as > + * we have 32 priorities. 0x20 then means that there are no > + * active priorities. > + */ > + highest_ap = __builtin_ctz(cpu_if->vgic_apr); __builtin_ctz(0) is undefined (https://gcc.gnu.org/onlinedocs/gcc/Bit-Operation-Builtins.html) Looking at __vgic_v3_clear_highest_active_priority(), it handles that like this: c0 = ap0 ? __ffs(ap0) : 32; Thanks, Joey > + > + /* > + * An interrupt is of sufficient priority if it is equal to or > + * greater than the priority mask. Add 1 to the priority mask > + * (i.e., lower priority) to match the APR logic before taking > + * the min. This gives us the lowest priority that is masked. > + */ > + priority_mask = FIELD_GET(FEAT_GCIE_ICH_VMCR_EL2_VPMR, cpu_if->vgic_vmcr); > + priority_mask = min(highest_ap, priority_mask + 1); > + > + return priority_mask; > +} > + > static bool vgic_v5_ppi_set_pending_state(struct kvm_vcpu *vcpu, > struct vgic_irq *irq) > { > @@ -121,6 +146,104 @@ void vgic_v5_set_ppi_ops(struct vgic_irq *irq) > irq->ops = &vgic_v5_ppi_irq_ops; > } > > + > +/* > + * Sync back the PPI priorities to the vgic_irq shadow state > + */ > +static void vgic_v5_sync_ppi_priorities(struct kvm_vcpu *vcpu) > +{ > + struct vgic_v5_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v5; > + unsigned long flags; > + int i, reg; > + > + /* We have 16 PPI Priority regs */ > + for (reg = 0; reg < 16; reg++) { > + const unsigned long priorityr = cpu_if->vgic_ppi_priorityr[reg]; > + > + for (i = 0; i < 8; ++i) { > + struct vgic_irq *irq; > + u32 intid; > + u8 priority; > + > + priority = (priorityr >> (i * 8)) & 0x1f; > + > + intid = FIELD_PREP(GICV5_HWIRQ_TYPE, GICV5_HWIRQ_TYPE_PPI); > + intid |= FIELD_PREP(GICV5_HWIRQ_ID, reg * 8 + i); > + > + irq = vgic_get_vcpu_irq(vcpu, intid); > + raw_spin_lock_irqsave(&irq->irq_lock, flags); > + > + irq->priority = priority; > + > + raw_spin_unlock_irqrestore(&irq->irq_lock, flags); > + vgic_put_irq(vcpu->kvm, irq); > + } > + } > +} > + > +bool vgic_v5_has_pending_ppi(struct kvm_vcpu *vcpu) > +{ > + struct vgic_v5_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v5; > + unsigned long flags; > + int i, reg; > + unsigned int priority_mask; > + > + /* If no pending bits are set, exit early */ > + if (likely(!cpu_if->vgic_ppi_pendr[0] && !cpu_if->vgic_ppi_pendr[1])) > + return false; > + > + priority_mask = vgic_v5_get_effective_priority_mask(vcpu); > + > + /* If the combined priority mask is 0, nothing can be signalled! */ > + if (!priority_mask) > + return false; > + > + /* The shadow priority is only updated on demand, sync it across first */ > + vgic_v5_sync_ppi_priorities(vcpu); > + > + for (reg = 0; reg < 2; reg++) { > + unsigned long possible_bits; > + const unsigned long enabler = cpu_if->vgic_ich_ppi_enabler_exit[reg]; > + const unsigned long pendr = cpu_if->vgic_ppi_pendr_exit[reg]; > + bool has_pending = false; > + > + /* Check all interrupts that are enabled and pending */ > + possible_bits = enabler & pendr; > + > + /* > + * Optimisation: pending and enabled with no active priorities > + */ > + if (possible_bits && priority_mask > 0x1f) > + return true; > + > + for_each_set_bit(i, &possible_bits, 64) { > + struct vgic_irq *irq; > + u32 intid; > + > + intid = FIELD_PREP(GICV5_HWIRQ_TYPE, GICV5_HWIRQ_TYPE_PPI); > + intid |= FIELD_PREP(GICV5_HWIRQ_ID, reg * 64 + i); > + > + irq = vgic_get_vcpu_irq(vcpu, intid); > + raw_spin_lock_irqsave(&irq->irq_lock, flags); > + > + /* > + * We know that the interrupt is enabled and pending, so > + * only check the priority. > + */ > + if (irq->priority <= priority_mask) > + has_pending = true; > + > + raw_spin_unlock_irqrestore(&irq->irq_lock, flags); > + vgic_put_irq(vcpu->kvm, irq); > + > + if (has_pending) > + return true; > + } > + } > + > + return false; > +} > + > /* > * Detect any PPIs state changes, and propagate the state with KVM's > * shadow structures. > diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c > index e534876656ca7..5d18a03cc11d5 100644 > --- a/arch/arm64/kvm/vgic/vgic.c > +++ b/arch/arm64/kvm/vgic/vgic.c > @@ -1174,11 +1174,15 @@ int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu) > unsigned long flags; > struct vgic_vmcr vmcr; > > - if (!vcpu->kvm->arch.vgic.enabled) > + if (!vcpu->kvm->arch.vgic.enabled && !vgic_is_v5(vcpu->kvm)) > return false; > > - if (vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last) > - return true; > + if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V5) { > + return vgic_v5_has_pending_ppi(vcpu); > + } else { > + if (vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last) > + return true; > + } > > vgic_get_vmcr(vcpu, &vmcr); > > diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h > index 5a77318ddb87a..4b3a1e7ca3fb4 100644 > --- a/arch/arm64/kvm/vgic/vgic.h > +++ b/arch/arm64/kvm/vgic/vgic.h > @@ -387,6 +387,7 @@ void vgic_debug_destroy(struct kvm *kvm); > int vgic_v5_probe(const struct gic_kvm_info *info); > void vgic_v5_set_ppi_ops(struct vgic_irq *irq); > int vgic_v5_set_ppi_dvi(struct kvm_vcpu *vcpu, u32 irq, bool dvi); > +bool vgic_v5_has_pending_ppi(struct kvm_vcpu *vcpu); > void vgic_v5_flush_ppi_state(struct kvm_vcpu *vcpu); > void vgic_v5_fold_irq_state(struct kvm_vcpu *vcpu); > void vgic_v5_load(struct kvm_vcpu *vcpu); > -- > 2.34.1