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

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Message-ID: <aD741hI7MfTmi7Rl@lpieralisi>
Date: Tue, 3 Jun 2025 15:29:58 +0200
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: Marc Zyngier <maz@...nel.org>
Cc: Zenghui Yu <yuzenghui@...wei.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Thomas Gleixner <tglx@...utronix.de>,
	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, Jun 03, 2025 at 01:50:47PM +0100, 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?
> 
> Thanks,
> 
> 	M.
> 
> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index d7ba8795d60f..89677a21d525 100644
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -287,7 +287,7 @@ static bool pci_create_device_domain(struct pci_dev *pdev, const struct msi_doma
>   *	- The device is removed
>   *	- MSI is disabled and a MSI-X domain is created
>   */
> -bool pci_setup_msi_device_domain(struct pci_dev *pdev)
> +bool pci_setup_msi_device_domain(struct pci_dev *pdev, unsigned int hwsize)
>  {
>  	if (WARN_ON_ONCE(pdev->msix_enabled))
>  		return false;
> @@ -297,7 +297,7 @@ bool pci_setup_msi_device_domain(struct pci_dev *pdev)
>  	if (pci_match_device_domain(pdev, DOMAIN_BUS_PCI_DEVICE_MSIX))
>  		msi_remove_device_irq_domain(&pdev->dev, MSI_DEFAULT_DOMAIN);
>  
> -	return pci_create_device_domain(pdev, &pci_msi_template, 1);
> +	return pci_create_device_domain(pdev, &pci_msi_template, hwsize);
>  }
>  
>  /**
> diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
> index 8b8848788618..81891701840a 100644
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -449,7 +449,7 @@ int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
>  	if (rc)
>  		return rc;
>  
> -	if (!pci_setup_msi_device_domain(dev))
> +	if (!pci_setup_msi_device_domain(dev, nvec))

If pci_msi_vec_count(dev) > maxvec we would cap nvec and size the
domain with the capped value.

In __pci_enable_msix_range() we are sizing the device according to
pci_msix_vec_count(dev) regardless of maxvec, if I read the code correctly.

While fixing it it would be good to make them consistent unless there is
a reason why they should not.

Lorenzo

>  		return -ENODEV;
>  
>  	for (;;) {
> diff --git a/drivers/pci/msi/msi.h b/drivers/pci/msi/msi.h
> index ee53cf079f4e..3ab898af88a7 100644
> --- a/drivers/pci/msi/msi.h
> +++ b/drivers/pci/msi/msi.h
> @@ -107,7 +107,7 @@ enum support_mode {
>  };
>  
>  bool pci_msi_domain_supports(struct pci_dev *dev, unsigned int feature_mask, enum support_mode mode);
> -bool pci_setup_msi_device_domain(struct pci_dev *pdev);
> +bool pci_setup_msi_device_domain(struct pci_dev *pdev, unsigned int hwsize);
>  bool pci_setup_msix_device_domain(struct pci_dev *pdev, unsigned int hwsize);
>  
>  /* Legacy (!IRQDOMAIN) fallbacks */
> 
> -- 
> Jazz isn't dead. It just smells funny.