Re: [PATCH v3 3/3] PCI/MSI: Convert pci_msi_ignore_mask to per MSI domain flag

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

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;
                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.