Re: [PATCH v3] PCI/AER: Handle Multi UnCorrectable/Correctable errors properly

[Sathyanarayanan Kuppuswamy]

On 5/11/22 4:40 PM, Bjorn Helgaas wrote:
> On Mon, Apr 18, 2022 at 03:02:37PM +0000, Kuppuswamy Sathyanarayanan wrote:
> > Currently the aer_irq() handler returns IRQ_NONE for cases without bits
> > PCI_ERR_ROOT_UNCOR_RCV or PCI_ERR_ROOT_COR_RCV are set. But this
> > assumption is incorrect.
> >
> > Consider a scenario where aer_irq() is triggered for a correctable
> > error, and while we process the error and before we clear the error
> > status in "Root Error Status" register, if the same kind of error
> > is triggered again, since aer_irq() only clears events it saw, the
> > multi-bit error is left in tact. This will cause the interrupt to fire
> > again, resulting in entering aer_irq() with just the multi-bit error
> > logged in the "Root Error Status" register.
> >
> > Repeated AER recovery test has revealed this condition does happen
> > and this prevents any new interrupt from being triggered. Allow to
> > process interrupt even if only multi-correctable (BIT 1) or
> > multi-uncorrectable bit (BIT 3) is set.
> >
> > Also note that, for cases with only multi-bit error is set, since this
> > is not the first occurrence of the error, PCI_ERR_ROOT_ERR_SRC may have
> > zero or some junk value. So we cannot cleanly process this error
> > information using aer_isr_one_error(). All we are attempting with this
> > fix is to make sure error interrupt processing can continue in this
> > scenario.
> >
> > This error can be reproduced by making following changes to the
> > aer_irq() function and by executing the given test commands.
> >
> >   static irqreturn_t aer_irq(int irq, void *context)
> >           struct aer_err_source e_src = {};
> >
> >           pci_read_config_dword(rp, aer + PCI_ERR_ROOT_STATUS,
> > 				&e_src.status);
> >   +       pci_dbg(pdev->port, "Root Error Status: %04x\n",
> >   +		e_src.status);
> >           if (!(e_src.status & AER_ERR_STATUS_MASK))
>
> Do you mean
>
>    if (!(e_src.status & (PCI_ERR_ROOT_UNCOR_RCV|PCI_ERR_ROOT_COR_RCV)))
>
> here?  AER_ERR_STATUS_MASK would be after this fix.

Yes. You are correct. Do you want me to update it and Fixes tag
and send next version?

> >                   return IRQ_NONE;
> >
> >   +       mdelay(5000);

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer