linux-kernel - Re: [PATCH v7 18/31] arm64: smp: Support non-SGIs for IPIs

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Message-ID: <aHZm8BsqV1ighJ+2@lpieralisi>
Date: Tue, 15 Jul 2025 16:34:24 +0200
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Sascha Bischoff <sascha.bischoff@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Timothy Hayes <timothy.hayes@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Peter Maydell <peter.maydell@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Jiri Slaby <jirislaby@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v7 18/31] arm64: smp: Support non-SGIs for IPIs

On Tue, Jul 15, 2025 at 07:10:29AM -0700, Breno Leitao wrote:
> Hello Lorenzo, Marc,
> 
> On Thu, Jul 03, 2025 at 12:25:08PM +0200, Lorenzo Pieralisi wrote:
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index 3b3f6b56e733..2c501e917d38 100644
> 
> > @@ -1046,11 +1068,15 @@ static void ipi_setup(int cpu)
> >  		return;
> >  
> >  	for (i = 0; i < nr_ipi; i++) {
> > -		if (ipi_should_be_nmi(i)) {
> > -			prepare_percpu_nmi(ipi_irq_base + i);
> > -			enable_percpu_nmi(ipi_irq_base + i, 0);
> > +		if (!percpu_ipi_descs) {
> > +			if (ipi_should_be_nmi(i)) {
> > +				prepare_percpu_nmi(ipi_irq_base + i);
> 
> I am testing linux-next on commit 0be23810e32e6d0 ("Add linux-next
> specific files for 20250714") on a Grace (GiCv3), and I am getting
> a bunch of those:
> 
> 	[    0.007992] WARNING: kernel/irq/manage.c:2599 at prepare_percpu_nmi+0x178/0x1b0, CPU#2: swapper/2/0
> 
> 	[    0.007996] pstate: 600003c9 (nZCv DAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> 	[    0.007997] pc : prepare_percpu_nmi (kernel/irq/manage.c:2599 (discriminator 1))
> 	[    0.007998] lr : prepare_percpu_nmi (kernel/irq/manage.c:2599 (discriminator 1))
> 
> 	[    0.008011] Call trace:
> 	[    0.008011] prepare_percpu_nmi (kernel/irq/manage.c:2599 (discriminator 1)) (P)
> 	[    0.008012] ipi_setup (arch/arm64/kernel/smp.c:1057)
> 	[    0.008014] secondary_start_kernel (arch/arm64/kernel/smp.c:245)
> 	[    0.008016] __secondary_switched (arch/arm64/kernel/head.S:405)
> 
> I haven't bissected the problem to this patch specifically, but
> I decided to share in case this is a known issue, given you are touching
> this code.
> 
> I would be happy to bissect it, in case it doesn't ring a bell.

Thank you for reporting it.

Does this patch below fix it ?

-- >8 --
diff --git i/arch/arm64/kernel/smp.c w/arch/arm64/kernel/smp.c
index 4797e2c70014..a900835a3adf 100644
--- i/arch/arm64/kernel/smp.c
+++ w/arch/arm64/kernel/smp.c
@@ -1093,7 +1093,7 @@ static void ipi_setup_sgi(int ipi)
 
 	irq = ipi_irq_base + ipi;
 
-	if (ipi_should_be_nmi(irq)) {
+	if (ipi_should_be_nmi(ipi)) {
 		err = request_percpu_nmi(irq, ipi_handler, "IPI", &irq_stat);
 		WARN(err, "Could not request IRQ %d as NMI, err=%d\n", irq, err);
 	} else {