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

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Date:   Wed, 11 May 2022 17:29:45 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Russell Currey <ruscur@...sell.cc>,
        Oliver OHalloran <oohall@...il.com>, linux-pci@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] PCI/AER: Handle Multi UnCorrectable/Correctable errors
 properly



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