linux-kernel - Re: [PATCH 16/16] PCI: vmd: Switch to msi_create_parent_irq

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Message-ID: <20250716203115.GA2553753@bhelgaas>
Date: Wed, 16 Jul 2025 15:31:15 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Nam Cao <namcao@...utronix.de>
Cc: Antonio Quartulli <antonio@...delbit.com>,
	Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Karthikeyan Mitran <m.karthikeyan@...iveil.co.in>,
	Hou Zhiqiang <Zhiqiang.Hou@....com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Pali Rohár <pali@...nel.org>,
	"K . Y . Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Joyce Ooi <joyce.ooi@...el.com>, Jim Quinlan <jim2101024@...il.com>,
	Nicolas Saenz Julienne <nsaenz@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
	Ryder Lee <ryder.lee@...iatek.com>,
	Jianjun Wang <jianjun.wang@...iatek.com>,
	Marek Vasut <marek.vasut+renesas@...il.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Michal Simek <michal.simek@....com>,
	Daire McNamara <daire.mcnamara@...rochip.com>,
	Nirmal Patel <nirmal.patel@...ux.intel.com>,
	Jonathan Derrick <jonathan.derrick@...ux.dev>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-arm-kernel@...ts.infradead.org, linux-hyperv@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH 16/16] PCI: vmd: Switch to msi_create_parent_irq_domain()

On Wed, Jul 16, 2025 at 10:12:16PM +0200, Nam Cao wrote:
> On Wed, Jul 16, 2025 at 09:52:05PM +0200, Antonio Quartulli wrote:
> > Hi Nam,
> Hi Antonio,
> 
> > On 26/06/2025 16:48, Nam Cao wrote:
> > [...]
> > > -static void vmd_msi_free(struct irq_domain *domain,
> > > -			struct msi_domain_info *info, unsigned int virq)
> > > +static void vmd_msi_free(struct irq_domain *domain, unsigned int virq, unsigned int nr_irqs)
> > >   {
> > >   	struct vmd_irq *vmdirq = irq_get_chip_data(virq);
> > > -	synchronize_srcu(&vmdirq->irq->srcu);
> > > +	for (int i = 0; i < nr_irqs; ++i) {
> > > +		synchronize_srcu(&vmdirq->irq->srcu);
> > > -	/* XXX: Potential optimization to rebalance */
> > > -	scoped_guard(raw_spinlock_irq, &list_lock)
> > > -		vmdirq->irq->count--;
> > > +		/* XXX: Potential optimization to rebalance */
> > > +		scoped_guard(raw_spinlock_irq, &list_lock)
> > > +			vmdirq->irq->count--;
> > > -	kfree(vmdirq);
> > > +		kfree(vmdirq);
> > > +	}
> > 
> > By introducing a for loop in this function, you are re-using vmdirq after
> > free'ing it.
> > 
> > I can't send a patch because I am not faimliar with this API and I don't
> > know how to fix it.
> > 
> > However, the issue was reported today by Coverity.
> > 
> > Any idea? :-)
> 
> Thanks for the report. That was indeed a mistake from my side.
> 
> I hope PCI maintainers don't mind squashing the below diff.

Squashed, thanks!  Updated commit:

  https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?id=4246b7fccf26

> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 48a6096cbbc0..50f0c91d561c 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -280,9 +280,11 @@ static int vmd_msi_alloc(struct irq_domain *domain, unsigned int virq,
>  static void vmd_msi_free(struct irq_domain *domain, unsigned int virq,
>  			 unsigned int nr_irqs)
>  {
> -	struct vmd_irq *vmdirq = irq_get_chip_data(virq);
> +	struct vmd_irq *vmdirq;
>  
>  	for (int i = 0; i < nr_irqs; ++i) {
> +		vmdirq = irq_get_chip_data(virq + i);
> +
>  		synchronize_srcu(&vmdirq->irq->srcu);
>  
>  		/* XXX: Potential optimization to rebalance */
>