linux-kernel - Re: [PATCH v2 3/5] genirq/msi: Move prepare() call to per-device allocation

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Message-ID: <87iklddkfp.wl-maz@kernel.org>
Date: Tue, 03 Jun 2025 14:27:38 +0100
From: Marc Zyngier <maz@...nel.org>
To: Zenghui Yu <yuzenghui@...wei.com>
Cc: <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lorenzo Pieralisi
	<lpieralisi@...nel.org>,
	Sascha Bischoff <sascha.bischoff@....com>,
	Timothy
 Hayes <timothy.hayes@....com>
Subject: Re: [PATCH v2 3/5] genirq/msi: Move prepare() call to per-device allocation

On Tue, 03 Jun 2025 14:07:04 +0100,
Zenghui Yu <yuzenghui@...wei.com> wrote:
> 
> Hi Marc,
> 
> On 2025/6/3 20:50, Marc Zyngier wrote:
> > Hi Zenghui,
> > 
> > On Tue, 03 Jun 2025 09:22:47 +0100,
> > Zenghui Yu <yuzenghui@...wei.com> wrote:
> > >
> > > > +	domain->dev = dev;
> > > > +	dev->msi.data->__domains[domid].domain = domain;
> > > > +
> > > > +	if (msi_domain_prepare_irqs(domain, dev, hwsize, &bundle->alloc_info)) {
> > >
> > > Does it work for MSI? hwsize is 1 in the MSI case, without taking
> > > pci_msi_vec_count() into account.
> > >
> > > bool pci_setup_msi_device_domain(struct pci_dev *pdev)
> > > {
> > > 	[...]
> > >
> > > 	return pci_create_device_domain(pdev, &pci_msi_template, 1);
> > 
> > Well spotted.
> > 
> > This looks like a PCI bug ignoring Multi-MSI. Can you give the
> > following a go and let people know whether that fixes your issue?
> 
> I hit this problem on Kunpeng920 with some HiSilicon SAS (Serial
> Attached SCSI controller) on it. These controllers are MSI-capable and
> didn't work after this commit.

That's interesting. It means that the sizing of the irqdomain to 1
wasn't getting in the way, even if that was obviously wrong. The funny
thing is that the msi_desc would still be OK, as we only have one for
MSI, no matter how many vectors are used.

>
> I have the exact same diff to get my box to work again ;-)

Ah ;-)

>
> Tested-by: Zenghui Yu <yuzenghui@...wei.com>
> 
> Thanks for your fix!

Thank you!

	M.

-- 
Jazz isn't dead. It just smells funny.