Re: [PATCH V4] PCI/MSI: Fix MSI hwirq truncation

[Vidya Sagar]

Hi Thomas,
Sorry to bother you.
Would you mind giving an Ack to this patch?

Thanks,
Vidya Sagar

On 1/23/2024 9:31 PM, Vidya Sagar wrote:
> Hi Thomas,
> Does this patch look fine to you?
> If yes, would you mind giving an Ack?
>
> Thanks,
> Vidya Sagar
>
> On 1/15/2024 7:26 PM, Vidya Sagar wrote:
> > While calculating the hwirq number for an MSI interrupt, the higher
> > bits (i.e. from bit-5 onwards a.k.a domain_nr >= 32) of the PCI domain
> > number gets truncated because of the shifted value casting to return
> > type of pci_domain_nr() which is 'int'. This for example is resulting
> > in same hwirq number for devices 0019:00:00.0 and 0039:00:00.0.
> >
> > So, cast the PCI domain number to 'irq_hw_number_t' before left shifting
> > it to calculate hwirq number. Please note that this fixes the issue only
> > on 64-bit systems and doesn't change the behavior in 32-bit systems i.e.
> > the 32-bit systems continue to have the issue. Since the issue surfaces
> > only if there are too many PCIe controllers in the system which usually
> > is the case in modern server systems and they don't tend to run 32-bit
> > kernels.
> >
> > Fixes: 3878eaefb89a ("PCI/MSI: Enhance core to support hierarchy 
> > irqdomain")
> > Tested-by: Shanker Donthineni <sdonthineni@xxxxxxxxxx>
> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > ---
> > V4:
> > * Added extra information in the change log about the impact of this 
> > patch
> >    in a 32-bit system as suggested by Thomas
> >
> > V3:
> > * Addressed review comments from Thomas Gleixner
> > * Added Tested-By: Shanker Donthineni <sdonthineni@xxxxxxxxxx>
> >
> > V2:
> > * Added Fixes tag
> >
> >   drivers/pci/msi/irqdomain.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> > index c8be056c248d..cfd84a899c82 100644
> > --- a/drivers/pci/msi/irqdomain.c
> > +++ b/drivers/pci/msi/irqdomain.c
> > @@ -61,7 +61,7 @@ static irq_hw_number_t 
> > pci_msi_domain_calc_hwirq(struct msi_desc *desc)
> >       return (irq_hw_number_t)desc->msi_index |
> >           pci_dev_id(dev) << 11 |
> > -        (pci_domain_nr(dev->bus) & 0xFFFFFFFF) << 27;
> > +        ((irq_hw_number_t)(pci_domain_nr(dev->bus) & 0xFFFFFFFF)) << 27;
> >   }
> >   static void pci_msi_domain_set_desc(msi_alloc_info_t *arg,