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

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Message-ID: <41f62ad1-fee7-3509-f670-b62db8c37843@linux.intel.com>
Date:   Wed, 11 May 2022 08:19:53 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Russell Currey <ruscur@...sell.cc>,
        Oliver OHalloran <oohall@...il.com>
Cc:     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

Hi Bjorn,

On 4/18/22 8:02 AM, 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))
>                   return IRQ_NONE;
> 
>   +       mdelay(5000);
> 
>   # Prep injection data for a correctable error.
>   $ cd /sys/kernel/debug/apei/einj
>   $ echo 0x00000040 > error_type
>   $ echo 0x4 > flags
>   $ echo 0x891000 > param4
> 
>   # Root Error Status is initially clear
>   $ setpci -s <Dev ID> ECAP0001+0x30.w
>   0000
> 
>   # Inject one error
>   $ echo 1 > error_inject
> 
>   # Interrupt received
>   pcieport <Dev ID>: AER: Root Error Status 0001
> 
>   # Inject another error (within 5 seconds)
>   $ echo 1 > error_inject
> 
>   # You will get a new IRQ with only multiple ERR_COR bit set
>   pcieport <Dev ID>: AER: Root Error Status 0002
> 
> Currently, the above issue has been only reproduced in the ICL server
> platform.
> 
> [Eric: proposed reproducing steps]
> Fixes: 4696b828ca37 ("PCI/AER: Hoist aerdrv.c, aer_inject.c up to drivers/pci/pcie/")
> Reported-by: Eric Badger <ebadger@...estorage.com>
> Reviewed-by: Ashok Raj <ashok.raj@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
> 

Any comments on this patch? I'm wondering whether you are expecting any
changes to be done to it. Please let me know.

> Changes since v2:
>   * Added more details to the commit log.
>   * Rebased on v5.18-rc1.
> 
> Changes since v1:
>   * Added Fixes tag.
>   * Included reproducing steps proposed by Eric.
> 
>   drivers/pci/pcie/aer.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 9fa1f97e5b27..7952e5efd6cf 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -101,6 +101,11 @@ struct aer_stats {
>   #define ERR_COR_ID(d)			(d & 0xffff)
>   #define ERR_UNCOR_ID(d)			(d >> 16)
>   
> +#define AER_ERR_STATUS_MASK		(PCI_ERR_ROOT_UNCOR_RCV |	\
> +					PCI_ERR_ROOT_COR_RCV |		\
> +					PCI_ERR_ROOT_MULTI_COR_RCV |	\
> +					PCI_ERR_ROOT_MULTI_UNCOR_RCV)
> +
>   static int pcie_aer_disable;
>   static pci_ers_result_t aer_root_reset(struct pci_dev *dev);
>   
> @@ -1196,7 +1201,7 @@ 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);
> -	if (!(e_src.status & (PCI_ERR_ROOT_UNCOR_RCV|PCI_ERR_ROOT_COR_RCV)))
> +	if (!(e_src.status & AER_ERR_STATUS_MASK))
>   		return IRQ_NONE;
>   
>   	pci_read_config_dword(rp, aer + PCI_ERR_ROOT_ERR_SRC, &e_src.id);

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer