linux-kernel - Re: [PATCH v3 3/3] PCI/MSI: Convert pci_msi_ignore

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Message-ID: <gu73hcbm5opv7wpdsbyyrends3dcxkzvran2asoepujlhfeqas@76rncc27opy2>
Date: Tue, 25 Mar 2025 10:47:14 +0100
From: Daniel Gomez <da.gomez@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Roger Pau Monné <roger.pau@...rix.com>, 
	Jürgen Groß <jgross@...e.com>, Bjorn Helgaas <helgaas@...nel.org>, linux-kernel@...r.kernel.org, 
	xen-devel@...ts.xenproject.org, linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 3/3] PCI/MSI: Convert pci_msi_ignore_mask to per MSI
 domain flag

On Tue, Mar 25, 2025 at 10:20:43AM +0100, Thomas Gleixner wrote:
> On Tue, Mar 25 2025 at 09:11, Thomas Gleixner wrote:
> 
> > On Mon, Mar 24 2025 at 20:18, Roger Pau Monné wrote:
> >> On Mon, Mar 24, 2025 at 07:58:14PM +0100, Daniel Gomez wrote:
> >>> The issue is that info appears to be uninitialized. So, this worked for me:
> >>
> >> Indeed, irq_domain->host_data is NULL, there's no msi_domain_info.  As
> >> this is x86, I was expecting x86 ot always use
> >> x86_init_dev_msi_info(), but that doesn't seem to be the case.  I
> >> would like to better understand this.
> >
> > Indeed. On x86 this should not happen at all. On architectures, which do
> > not use (hierarchical) interrupt domains, it will return NULL.
> >
> > So I really want to understand why this happens on x86 before such a
> > "fix" is deployed.
> 
> So after staring at it some more it's clear. Without XEN, the domain
> returned is the MSI parent domain, which is the vector domain in that
> setup. That does not have a domain info set. But on legacy architectures
> there is not even a domain.
> 
> It's really wonderful that we have a gazillion ways to manage the
> backends of PCI/MSI....
> 
> So none of the suggested pointer checks will cover it correctly. Though
> there is already a function which allows to query MSI domain flags
> independent of the underlying insanity. Sorry for not catching it in
> review.
> 
> Untested patch below.
> 
> Thanks,
> 
>         tglx
> ---
>  drivers/pci/msi/msi.c |   18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
> 
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -285,8 +285,6 @@ static void pci_msi_set_enable(struct pc
>  static int msi_setup_msi_desc(struct pci_dev *dev, int nvec,
>  			      struct irq_affinity_desc *masks)
>  {
> -	const struct irq_domain *d = dev_get_msi_domain(&dev->dev);
> -	const struct msi_domain_info *info = d->host_data;
>  	struct msi_desc desc;
>  	u16 control;
>  
> @@ -297,7 +295,7 @@ static int msi_setup_msi_desc(struct pci
>  	/* Lies, damned lies, and MSIs */
>  	if (dev->dev_flags & PCI_DEV_FLAGS_HAS_MSI_MASKING)
>  		control |= PCI_MSI_FLAGS_MASKBIT;
> -	if (info->flags & MSI_FLAG_NO_MASK)
> +	if (pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY))
>  		control &= ~PCI_MSI_FLAGS_MASKBIT;
>  
>  	desc.nvec_used			= nvec;
> @@ -605,20 +603,18 @@ static void __iomem *msix_map_region(str
>   */
>  void msix_prepare_msi_desc(struct pci_dev *dev, struct msi_desc *desc)
>  {
> -	const struct irq_domain *d = dev_get_msi_domain(&dev->dev);
> -	const struct msi_domain_info *info = d->host_data;
> -
>  	desc->nvec_used				= 1;
>  	desc->pci.msi_attrib.is_msix		= 1;
>  	desc->pci.msi_attrib.is_64		= 1;
>  	desc->pci.msi_attrib.default_irq	= dev->irq;
>  	desc->pci.mask_base			= dev->msix_base;
> -	desc->pci.msi_attrib.can_mask		= !(info->flags & MSI_FLAG_NO_MASK) &&
> -						  !desc->pci.msi_attrib.is_virtual;
>  
> -	if (desc->pci.msi_attrib.can_mask) {
> +
> +	if (!pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY) &&
> +	    !desc->pci.msi_attrib.is_virtual) {
>  		void __iomem *addr = pci_msix_desc_addr(desc);
>  
> +		desc->pci.msi_attrib.can_mask = true;

can_mask is u8.

>  		desc->pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
>  	}
>  }
> @@ -715,8 +711,6 @@ static int msix_setup_interrupts(struct
>  static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
>  				int nvec, struct irq_affinity *affd)
>  {
> -	const struct irq_domain *d = dev_get_msi_domain(&dev->dev);
> -	const struct msi_domain_info *info = d->host_data;
>  	int ret, tsize;
>  	u16 control;
>  
> @@ -747,7 +741,7 @@ static int msix_capability_init(struct p
>  	/* Disable INTX */
>  	pci_intx_for_msi(dev, 0);
>  
> -	if (!(info->flags & MSI_FLAG_NO_MASK)) {
> +	if (!pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY)) {
>  		/*
>  		 * Ensure that all table entries are masked to prevent
>  		 * stale entries from firing in a crash kernel.

It works, thanks!

For the final patch:

Tested-by: Daniel Gomez <da.gomez@...sung.com>

Daniel