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

[Bjorn Helgaas]

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.

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