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

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Message-ID: <87frggex3d.wl-maz@kernel.org>
Date: Tue, 03 Jun 2025 15:08:54 +0100
From: Marc Zyngier <maz@...nel.org>
To: Lorenzo Pieralisi <lpieralisi@...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, 03 Jun 2025 15:03:26 +0100,
Marc Zyngier <maz@...nel.org> wrote:
> 
> On Tue, 03 Jun 2025 14:29:58 +0100,
> Lorenzo Pieralisi <lpieralisi@...nel.org> wrote:
> > 
> > > +	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.
> 
> This is indeed odd, but that'd be a separate fix. Something like:
> 
> diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
> index 2090eef64b14..6ede55a7c5e6 100644
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -439,9 +439,6 @@ int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
>  	if (nvec < minvec)
>  		return -ENOSPC;
>  
> -	if (nvec > maxvec)
> -		nvec = maxvec;
> -
>  	rc = pci_setup_msi_context(dev);
>  	if (rc)
>  		return rc;
> @@ -449,6 +446,9 @@ int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
>  	if (!pci_setup_msi_device_domain(dev, nvec))
>  		return -ENODEV;
>  
> +	if (nvec > maxvec)
> +		nvec = maxvec;
> +
>  	for (;;) {
>  		if (affd) {
>  			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
> 

Actually, let's lump the two together. There is no reason to wait.

	M.

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