Re: [PATCH V2] PCI/MSI: Set device flag indicating only 32-bit MSI support

[Vidya Sagar]

On 12/3/2020 11:54 PM, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
>
>
> On Tue, Nov 24, 2020 at 04:20:35PM +0530, Vidya Sagar wrote:
> > There are devices (Ex:- Marvell SATA controller) that don't support
> > 64-bit MSIs and the same is advertised through their MSI capability
> > register. Set no_64bit_msi flag explicitly for such devices in the
> > MSI setup code so that the msi_verify_entries() API would catch
> > if the MSI arch code tries to use 64-bit MSI.
>
> This seems good to me.  I'll post a possible revision to set
> dev->no_64bit_msi in the device enumeration path instead of in the IRQ
> allocation path, since it's really a property of the device, not of
> the msi_desc.
>
> I like the extra checking this gives us.  Was this prompted by
> tripping over something, or is it something you noticed by code
> reading?  If the former, a hint about what was wrong and how it's
> being fixed would be useful.
I observed functionality issue with Marvell SATA controller (1b4b:9171) 
when the allocated MSI target address was a 64-bit address. I mentioned 
the Marvell SATA controller as an example in the commit message.

Thanks,
Vidya Sagar

> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > ---
> > V2:
> > * Addressed Bjorn's comment and changed the error message
> >
> >   drivers/pci/msi.c | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > index d52d118979a6..8de5ba6b4a59 100644
> > --- a/drivers/pci/msi.c
> > +++ b/drivers/pci/msi.c
> > @@ -581,10 +581,12 @@ msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)
> >        entry->msi_attrib.multi_cap     = (control & PCI_MSI_FLAGS_QMASK) >> 1;
> >        entry->msi_attrib.multiple      = ilog2(__roundup_pow_of_two(nvec));
> >
> > -     if (control & PCI_MSI_FLAGS_64BIT)
> > +     if (control & PCI_MSI_FLAGS_64BIT) {
> >                entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
> > -     else
> > +     } else {
> >                entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_32;
> > +             dev->no_64bit_msi = 1;
> > +     }
> >
> >        /* Save the initial mask status */
> >        if (entry->msi_attrib.maskbit)
> > @@ -602,8 +604,9 @@ static int msi_verify_entries(struct pci_dev *dev)
> >        for_each_pci_msi_entry(entry, dev) {
> >                if (!dev->no_64bit_msi || !entry->msg.address_hi)
> >                        continue;
> > -             pci_err(dev, "Device has broken 64-bit MSI but arch"
> > -                     " tried to assign one above 4G\n");
> > +             pci_err(dev, "Device has either broken 64-bit MSI or "
> > +                     "only 32-bit MSI support but "
> > +                     "arch tried to assign one above 4G\n");
> >                return -EIO;
> >        }
> >        return 0;
> > --
> > 2.17.1