[v11,1/8] PCI/ERR: Update error status after reset_link()
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Message ID a2e57496135fcfc1dab8d201cb49f5717e7459a4.1577400653.git.sathyanarayanan.kuppuswamy@linux.intel.com
State New
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Series
  • Add Error Disconnect Recover (EDR) support
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Commit Message

Kuppuswamy, Sathyanarayanan Dec. 27, 2019, 12:39 a.m. UTC
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
reset_link() to recover from fatal errors. But, if the reset is
successful there is no need to continue the rest of the error recovery
checks. Also, during fatal error recovery, if the initial value of error
status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
even after successful recovery (using reset_link()) pcie_do_recovery()
will report the recovery result as failure. So update the status of
error after reset_link().

Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Keith Busch <keith.busch@intel.com>
---
 drivers/pci/pcie/err.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

Comments

Bjorn Helgaas Jan. 4, 2020, 12:34 a.m. UTC | #1
On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> 
> Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
> reset_link() to recover from fatal errors. But, if the reset is
> successful there is no need to continue the rest of the error recovery
> checks. Also, during fatal error recovery, if the initial value of error
> status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
> even after successful recovery (using reset_link()) pcie_do_recovery()
> will report the recovery result as failure. So update the status of
> error after reset_link().

I like the part about updating "status" with the result of
reset_link(), and I split that into its own patch because it
seems like a fix that *can* be separated.

But I'm not convinced that we should skip the ->slot_reset()
callbacks if the reset_link() was successful.  According to
Documentation/PCI/pci-error-recovery.rst, we should call
->slot_reset() after completion of the reset.

For example, rsxx_err_handler implements ->slot_reset(), but
not ->resume().  If we reset the device, we'll claim success and
return, but we won't call rsxx_slot_reset(), which does a bunch
of important-looking recovery stuff.

If pci-error-recovery.rst is wrong, we should fix that (after
auditing all the drivers to make sure they match).

> Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Keith Busch <keith.busch@intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Acked-by: Keith Busch <keith.busch@intel.com>
> ---
>  drivers/pci/pcie/err.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index b0e6048a9208..53cd9200ec2c 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>  	else
>  		pci_walk_bus(bus, report_normal_detected, &status);
>  
> -	if (state == pci_channel_io_frozen &&
> -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
> -		goto failed;
> +	if (state == pci_channel_io_frozen) {
> +		status = reset_link(dev, service);
> +		if (status != PCI_ERS_RESULT_RECOVERED)
> +			goto failed;
> +		goto done;
> +	}
>  
>  	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>  		status = PCI_ERS_RESULT_RECOVERED;
> @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>  	if (status != PCI_ERS_RESULT_RECOVERED)
>  		goto failed;
>  
> +done:
>  	pci_dbg(dev, "broadcast resume message\n");
>  	pci_walk_bus(bus, report_resume, &status);
>  
> -- 
> 2.21.0
>
Kuppuswamy, Sathyanarayanan Jan. 4, 2020, 1:03 a.m. UTC | #2
On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
> On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>
>> Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
>> reset_link() to recover from fatal errors. But, if the reset is
>> successful there is no need to continue the rest of the error recovery
>> checks. Also, during fatal error recovery, if the initial value of error
>> status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
>> even after successful recovery (using reset_link()) pcie_do_recovery()
>> will report the recovery result as failure. So update the status of
>> error after reset_link().
> I like the part about updating "status" with the result of
> reset_link(), and I split that into its own patch because it
> seems like a fix that *can* be separated.
>
> But I'm not convinced that we should skip the ->slot_reset()
> callbacks if the reset_link() was successful.
If reset_link() call is successful then the result value will be
"PCI_ERS_RESULT_RECOVERED". So even if you proceed with
rest of the code, slot_reset() will never get called right ?
>    According to
> Documentation/PCI/pci-error-recovery.rst, we should call
> ->slot_reset() after completion of the reset.
>
> For example, rsxx_err_handler implements ->slot_reset(), but
> not ->resume().  If we reset the device, we'll claim success and
> return, but we won't call rsxx_slot_reset(), which does a bunch
> of important-looking recovery stuff.
>
> If pci-error-recovery.rst is wrong, we should fix that (after
> auditing all the drivers to make sure they match).
>
>> Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
>> Cc: Ashok Raj <ashok.raj@intel.com>
>> Cc: Keith Busch <keith.busch@intel.com>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>> Acked-by: Keith Busch <keith.busch@intel.com>
>> ---
>>   drivers/pci/pcie/err.c | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index b0e6048a9208..53cd9200ec2c 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>   	else
>>   		pci_walk_bus(bus, report_normal_detected, &status);
>>   
>> -	if (state == pci_channel_io_frozen &&
>> -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>> -		goto failed;
>> +	if (state == pci_channel_io_frozen) {
>> +		status = reset_link(dev, service);
>> +		if (status != PCI_ERS_RESULT_RECOVERED)
>> +			goto failed;
>> +		goto done;
>> +	}
>>   
>>   	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>>   		status = PCI_ERS_RESULT_RECOVERED;
>> @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>   	if (status != PCI_ERS_RESULT_RECOVERED)
>>   		goto failed;
>>   
>> +done:
>>   	pci_dbg(dev, "broadcast resume message\n");
>>   	pci_walk_bus(bus, report_resume, &status);
>>   
>> -- 
>> 2.21.0
>>
Bjorn Helgaas Jan. 4, 2020, 2:54 a.m. UTC | #3
On Fri, Jan 03, 2020 at 05:03:03PM -0800, Kuppuswamy Sathyanarayanan wrote:
> On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
> > On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> > > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > 
> > > Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
> > > reset_link() to recover from fatal errors. But, if the reset is
> > > successful there is no need to continue the rest of the error recovery
> > > checks. Also, during fatal error recovery, if the initial value of error
> > > status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
> > > even after successful recovery (using reset_link()) pcie_do_recovery()
> > > will report the recovery result as failure. So update the status of
> > > error after reset_link().
> > I like the part about updating "status" with the result of
> > reset_link(), and I split that into its own patch because it
> > seems like a fix that *can* be separated.
> > 
> > But I'm not convinced that we should skip the ->slot_reset()
> > callbacks if the reset_link() was successful.
>
> If reset_link() call is successful then the result value will be
> "PCI_ERS_RESULT_RECOVERED". So even if you proceed with
> rest of the code, slot_reset() will never get called right ?

The current code:

        if (state == pci_channel_io_frozen &&
            reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
                goto failed;
        ...
        if (status == PCI_ERS_RESULT_NEED_RESET) {
                status = PCI_ERS_RESULT_RECOVERED;
                pci_walk_bus(bus, report_slot_reset, &status);

doesn't save the result of reset_link(), so if status was
PCI_ERS_RESULT_NEED_RESET and the reset succeeds, we will call
->slot_reset().

After your patch, if "state == pci_channel_io_frozen", we *never* call
->slot_reset().

Do you think that matches pci-error-recovery.rst?  It doesn't seem
like it to me, but perhaps I haven't read it closely enough.

> > According to
> > Documentation/PCI/pci-error-recovery.rst, we should call
> > ->slot_reset() after completion of the reset.
> > 
> > For example, rsxx_err_handler implements ->slot_reset(), but
> > not ->resume().  If we reset the device, we'll claim success and
> > return, but we won't call rsxx_slot_reset(), which does a bunch
> > of important-looking recovery stuff.
> > 
> > If pci-error-recovery.rst is wrong, we should fix that (after
> > auditing all the drivers to make sure they match).
> > 
> > > Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
> > > Cc: Ashok Raj <ashok.raj@intel.com>
> > > Cc: Keith Busch <keith.busch@intel.com>
> > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > Acked-by: Keith Busch <keith.busch@intel.com>
> > > ---
> > >   drivers/pci/pcie/err.c | 10 +++++++---
> > >   1 file changed, 7 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > > index b0e6048a9208..53cd9200ec2c 100644
> > > --- a/drivers/pci/pcie/err.c
> > > +++ b/drivers/pci/pcie/err.c
> > > @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
> > >   	else
> > >   		pci_walk_bus(bus, report_normal_detected, &status);
> > > -	if (state == pci_channel_io_frozen &&
> > > -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
> > > -		goto failed;
> > > +	if (state == pci_channel_io_frozen) {
> > > +		status = reset_link(dev, service);
> > > +		if (status != PCI_ERS_RESULT_RECOVERED)
> > > +			goto failed;
> > > +		goto done;
> > > +	}
> > >   	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
> > >   		status = PCI_ERS_RESULT_RECOVERED;
> > > @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
> > >   	if (status != PCI_ERS_RESULT_RECOVERED)
> > >   		goto failed;
> > > +done:
> > >   	pci_dbg(dev, "broadcast resume message\n");
> > >   	pci_walk_bus(bus, report_resume, &status);
> > > -- 
> > > 2.21.0
> > > 
> -- 
> Sathyanarayanan Kuppuswamy
> Linux kernel developer
>
Kuppuswamy, Sathyanarayanan Jan. 9, 2020, 12:14 a.m. UTC | #4
Hi Bjorn,

Thanks for the comments.

On 1/3/20 6:54 PM, Bjorn Helgaas wrote:
> On Fri, Jan 03, 2020 at 05:03:03PM -0800, Kuppuswamy Sathyanarayanan wrote:
>> On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
>>> On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>>
>>>> Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
>>>> reset_link() to recover from fatal errors. But, if the reset is
>>>> successful there is no need to continue the rest of the error recovery
>>>> checks. Also, during fatal error recovery, if the initial value of error
>>>> status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
>>>> even after successful recovery (using reset_link()) pcie_do_recovery()
>>>> will report the recovery result as failure. So update the status of
>>>> error after reset_link().
>>> I like the part about updating "status" with the result of
>>> reset_link(), and I split that into its own patch because it
>>> seems like a fix that *can* be separated.
>>>
>>> But I'm not convinced that we should skip the ->slot_reset()
>>> callbacks if the reset_link() was successful.
>> If reset_link() call is successful then the result value will be
>> "PCI_ERS_RESULT_RECOVERED". So even if you proceed with
>> rest of the code, slot_reset() will never get called right ?
> The current code:
>
>          if (state == pci_channel_io_frozen &&
>              reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>                  goto failed;
>          ...
>          if (status == PCI_ERS_RESULT_NEED_RESET) {
>                  status = PCI_ERS_RESULT_RECOVERED;
>                  pci_walk_bus(bus, report_slot_reset, &status);
>
> doesn't save the result of reset_link(), so if status was
> PCI_ERS_RESULT_NEED_RESET and the reset succeeds, we will call
> ->slot_reset().
>
> After your patch, if "state == pci_channel_io_frozen", we *never* call
> ->slot_reset().
>
> Do you think that matches pci-error-recovery.rst?  It doesn't seem
> like it to me, but perhaps I haven't read it closely enough.
Documentation does not have clear details on what to do with return
value of reset_link() ( step 3). But IMO, if step 3 recovers the device and
returns PCI_ERS_RESULT_RECOVERED then there is no need to proceed
to slot reset (step 4). May be we should update the Documentation ?

Keith,
You have any comments ?
>
>>> According to
>>> Documentation/PCI/pci-error-recovery.rst, we should call
>>> ->slot_reset() after completion of the reset.
>>>
>>> For example, rsxx_err_handler implements ->slot_reset(), but
>>> not ->resume().  If we reset the device, we'll claim success and
>>> return, but we won't call rsxx_slot_reset(), which does a bunch
>>> of important-looking recovery stuff.
>>>
>>> If pci-error-recovery.rst is wrong, we should fix that (after
>>> auditing all the drivers to make sure they match).
>>>
>>>> Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
>>>> Cc: Ashok Raj <ashok.raj@intel.com>
>>>> Cc: Keith Busch <keith.busch@intel.com>
>>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>> Acked-by: Keith Busch <keith.busch@intel.com>
>>>> ---
>>>>    drivers/pci/pcie/err.c | 10 +++++++---
>>>>    1 file changed, 7 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>>>> index b0e6048a9208..53cd9200ec2c 100644
>>>> --- a/drivers/pci/pcie/err.c
>>>> +++ b/drivers/pci/pcie/err.c
>>>> @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>>>    	else
>>>>    		pci_walk_bus(bus, report_normal_detected, &status);
>>>> -	if (state == pci_channel_io_frozen &&
>>>> -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>>>> -		goto failed;
>>>> +	if (state == pci_channel_io_frozen) {
>>>> +		status = reset_link(dev, service);
>>>> +		if (status != PCI_ERS_RESULT_RECOVERED)
>>>> +			goto failed;
>>>> +		goto done;
>>>> +	}
>>>>    	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>>>>    		status = PCI_ERS_RESULT_RECOVERED;
>>>> @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>>>    	if (status != PCI_ERS_RESULT_RECOVERED)
>>>>    		goto failed;
>>>> +done:
>>>>    	pci_dbg(dev, "broadcast resume message\n");
>>>>    	pci_walk_bus(bus, report_resume, &status);
>>>> -- 
>>>> 2.21.0
>>>>
>> -- 
>> Sathyanarayanan Kuppuswamy
>> Linux kernel developer
>>
Bjorn Helgaas Jan. 9, 2020, 11:26 p.m. UTC | #5
On Wed, Jan 08, 2020 at 04:14:09PM -0800, Kuppuswamy Sathyanarayanan wrote:
> On 1/3/20 6:54 PM, Bjorn Helgaas wrote:
> > On Fri, Jan 03, 2020 at 05:03:03PM -0800, Kuppuswamy Sathyanarayanan wrote:
> > > On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
> > > > On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> > > > > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > > > 
> > > > > Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
> > > > > reset_link() to recover from fatal errors. But, if the reset is
> > > > > successful there is no need to continue the rest of the error recovery
> > > > > checks. Also, during fatal error recovery, if the initial value of error
> > > > > status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
> > > > > even after successful recovery (using reset_link()) pcie_do_recovery()
> > > > > will report the recovery result as failure. So update the status of
> > > > > error after reset_link().
> > > > I like the part about updating "status" with the result of
> > > > reset_link(), and I split that into its own patch because it
> > > > seems like a fix that *can* be separated.
> > > > 
> > > > But I'm not convinced that we should skip the ->slot_reset()
> > > > callbacks if the reset_link() was successful.
> > > If reset_link() call is successful then the result value will be
> > > "PCI_ERS_RESULT_RECOVERED". So even if you proceed with
> > > rest of the code, slot_reset() will never get called right ?
> > The current code:
> > 
> >          if (state == pci_channel_io_frozen &&
> >              reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
> >                  goto failed;
> >          ...
> >          if (status == PCI_ERS_RESULT_NEED_RESET) {
> >                  status = PCI_ERS_RESULT_RECOVERED;
> >                  pci_walk_bus(bus, report_slot_reset, &status);
> > 
> > doesn't save the result of reset_link(), so if status was
> > PCI_ERS_RESULT_NEED_RESET and the reset succeeds, we will call
> > ->slot_reset().
> > 
> > After your patch, if "state == pci_channel_io_frozen", we *never* call
> > ->slot_reset().
> > 
> > Do you think that matches pci-error-recovery.rst?  It doesn't seem
> > like it to me, but perhaps I haven't read it closely enough.
> Documentation does not have clear details on what to do with return
> value of reset_link() (step 3). But IMO, if step 3 recovers the device and
> returns PCI_ERS_RESULT_RECOVERED then there is no need to proceed
> to slot reset (step 4). May be we should update the Documentation?

Are you suggesting we don't need to call a driver callback after
resetting the device?  Note that the ->slot_reset() doesn't *perform*
a reset; it is called *after* completion of a reset.

The doc says:

  ... Upon completion of slot reset, the platform will call the device
  slot_reset() callback.
  ...
  This call gives drivers the chance to re-initialize the hardware
  (re-download firmware, etc.).  At this point, the driver may assume
  that the card is in a fresh state and is fully functional. The slot
  is unfrozen and the driver has full access to PCI config space,
  memory mapped I/O space and DMA. Interrupts (Legacy, MSI, or MSI-X)
  will also be available.

After we reset a device, the driver certainly needs a chance to
reinitialize it.

> > > > According to
> > > > Documentation/PCI/pci-error-recovery.rst, we should call
> > > > ->slot_reset() after completion of the reset.
> > > > 
> > > > For example, rsxx_err_handler implements ->slot_reset(), but
> > > > not ->resume().  If we reset the device, we'll claim success and
> > > > return, but we won't call rsxx_slot_reset(), which does a bunch
> > > > of important-looking recovery stuff.
> > > > 
> > > > If pci-error-recovery.rst is wrong, we should fix that (after
> > > > auditing all the drivers to make sure they match).
> > > > 
> > > > > Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
> > > > > Cc: Ashok Raj <ashok.raj@intel.com>
> > > > > Cc: Keith Busch <keith.busch@intel.com>
> > > > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > > > Acked-by: Keith Busch <keith.busch@intel.com>
> > > > > ---
> > > > >    drivers/pci/pcie/err.c | 10 +++++++---
> > > > >    1 file changed, 7 insertions(+), 3 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > > > > index b0e6048a9208..53cd9200ec2c 100644
> > > > > --- a/drivers/pci/pcie/err.c
> > > > > +++ b/drivers/pci/pcie/err.c
> > > > > @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
> > > > >    	else
> > > > >    		pci_walk_bus(bus, report_normal_detected, &status);
> > > > > -	if (state == pci_channel_io_frozen &&
> > > > > -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
> > > > > -		goto failed;
> > > > > +	if (state == pci_channel_io_frozen) {
> > > > > +		status = reset_link(dev, service);
> > > > > +		if (status != PCI_ERS_RESULT_RECOVERED)
> > > > > +			goto failed;
> > > > > +		goto done;
> > > > > +	}
> > > > >    	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
> > > > >    		status = PCI_ERS_RESULT_RECOVERED;
> > > > > @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
> > > > >    	if (status != PCI_ERS_RESULT_RECOVERED)
> > > > >    		goto failed;
> > > > > +done:
> > > > >    	pci_dbg(dev, "broadcast resume message\n");
> > > > >    	pci_walk_bus(bus, report_resume, &status);
> > > > > -- 
> > > > > 2.21.0
> > > > > 
> > > -- 
> > > Sathyanarayanan Kuppuswamy
> > > Linux kernel developer
> > > 
> -- 
> Sathyanarayanan Kuppuswamy
> Linux kernel developer
>
Kuppuswamy, Sathyanarayanan Jan. 10, 2020, 1:08 a.m. UTC | #6
On 1/9/20 3:26 PM, Bjorn Helgaas wrote:
> On Wed, Jan 08, 2020 at 04:14:09PM -0800, Kuppuswamy Sathyanarayanan wrote:
>> On 1/3/20 6:54 PM, Bjorn Helgaas wrote:
>>> On Fri, Jan 03, 2020 at 05:03:03PM -0800, Kuppuswamy Sathyanarayanan wrote:
>>>> On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
>>>>> On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>>>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>>>>
>>>>>> Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
>>>>>> reset_link() to recover from fatal errors. But, if the reset is
>>>>>> successful there is no need to continue the rest of the error recovery
>>>>>> checks. Also, during fatal error recovery, if the initial value of error
>>>>>> status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
>>>>>> even after successful recovery (using reset_link()) pcie_do_recovery()
>>>>>> will report the recovery result as failure. So update the status of
>>>>>> error after reset_link().
>>>>> I like the part about updating "status" with the result of
>>>>> reset_link(), and I split that into its own patch because it
>>>>> seems like a fix that *can* be separated.
>>>>>
>>>>> But I'm not convinced that we should skip the ->slot_reset()
>>>>> callbacks if the reset_link() was successful.
>>>> If reset_link() call is successful then the result value will be
>>>> "PCI_ERS_RESULT_RECOVERED". So even if you proceed with
>>>> rest of the code, slot_reset() will never get called right ?
>>> The current code:
>>>
>>>           if (state == pci_channel_io_frozen &&
>>>               reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>>>                   goto failed;
>>>           ...
>>>           if (status == PCI_ERS_RESULT_NEED_RESET) {
>>>                   status = PCI_ERS_RESULT_RECOVERED;
>>>                   pci_walk_bus(bus, report_slot_reset, &status);
>>>
>>> doesn't save the result of reset_link(), so if status was
>>> PCI_ERS_RESULT_NEED_RESET and the reset succeeds, we will call
>>> ->slot_reset().
>>>
>>> After your patch, if "state == pci_channel_io_frozen", we *never* call
>>> ->slot_reset().
>>>
>>> Do you think that matches pci-error-recovery.rst?  It doesn't seem
>>> like it to me, but perhaps I haven't read it closely enough.
>> Documentation does not have clear details on what to do with return
>> value of reset_link() (step 3). But IMO, if step 3 recovers the device and
>> returns PCI_ERS_RESULT_RECOVERED then there is no need to proceed
>> to slot reset (step 4). May be we should update the Documentation?
> Are you suggesting we don't need to call a driver callback after
> resetting the device?  Note that the ->slot_reset() doesn't *perform*
> a reset; it is called *after* completion of a reset.
>
> The doc says:
>
>    ... Upon completion of slot reset, the platform will call the device
>    slot_reset() callback.
>    ...
>    This call gives drivers the chance to re-initialize the hardware
>    (re-download firmware, etc.).  At this point, the driver may assume
>    that the card is in a fresh state and is fully functional. The slot
>    is unfrozen and the driver has full access to PCI config space,
>    memory mapped I/O space and DMA. Interrupts (Legacy, MSI, or MSI-X)
>    will also be available.
Got it. Let me fix it in next version.
But, will this sequence apply for fatal error recovery (triggered from 
DPC code path) ? I think the device is removed and re-added in hotplug 
path (DLLSC transition).
>
> After we reset a device, the driver certainly needs a chance to
> reinitialize it.
>
>>>>> According to
>>>>> Documentation/PCI/pci-error-recovery.rst, we should call
>>>>> ->slot_reset() after completion of the reset.
>>>>>
>>>>> For example, rsxx_err_handler implements ->slot_reset(), but
>>>>> not ->resume().  If we reset the device, we'll claim success and
>>>>> return, but we won't call rsxx_slot_reset(), which does a bunch
>>>>> of important-looking recovery stuff.
>>>>>
>>>>> If pci-error-recovery.rst is wrong, we should fix that (after
>>>>> auditing all the drivers to make sure they match).
>>>>>
>>>>>> Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
>>>>>> Cc: Ashok Raj <ashok.raj@intel.com>
>>>>>> Cc: Keith Busch <keith.busch@intel.com>
>>>>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>>>> Acked-by: Keith Busch <keith.busch@intel.com>
>>>>>> ---
>>>>>>     drivers/pci/pcie/err.c | 10 +++++++---
>>>>>>     1 file changed, 7 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>>>>>> index b0e6048a9208..53cd9200ec2c 100644
>>>>>> --- a/drivers/pci/pcie/err.c
>>>>>> +++ b/drivers/pci/pcie/err.c
>>>>>> @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>>>>>     	else
>>>>>>     		pci_walk_bus(bus, report_normal_detected, &status);
>>>>>> -	if (state == pci_channel_io_frozen &&
>>>>>> -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>>>>>> -		goto failed;
>>>>>> +	if (state == pci_channel_io_frozen) {
>>>>>> +		status = reset_link(dev, service);
>>>>>> +		if (status != PCI_ERS_RESULT_RECOVERED)
>>>>>> +			goto failed;
>>>>>> +		goto done;
>>>>>> +	}
>>>>>>     	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>>>>>>     		status = PCI_ERS_RESULT_RECOVERED;
>>>>>> @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>>>>>     	if (status != PCI_ERS_RESULT_RECOVERED)
>>>>>>     		goto failed;
>>>>>> +done:
>>>>>>     	pci_dbg(dev, "broadcast resume message\n");
>>>>>>     	pci_walk_bus(bus, report_resume, &status);
>>>>>> -- 
>>>>>> 2.21.0
>>>>>>
>>>> -- 
>>>> Sathyanarayanan Kuppuswamy
>>>> Linux kernel developer
>>>>
>> -- 
>> Sathyanarayanan Kuppuswamy
>> Linux kernel developer
>>

Patch
diff mbox series

diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index b0e6048a9208..53cd9200ec2c 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -204,9 +204,12 @@  void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
 	else
 		pci_walk_bus(bus, report_normal_detected, &status);
 
-	if (state == pci_channel_io_frozen &&
-	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
-		goto failed;
+	if (state == pci_channel_io_frozen) {
+		status = reset_link(dev, service);
+		if (status != PCI_ERS_RESULT_RECOVERED)
+			goto failed;
+		goto done;
+	}
 
 	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
 		status = PCI_ERS_RESULT_RECOVERED;
@@ -228,6 +231,7 @@  void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
 	if (status != PCI_ERS_RESULT_RECOVERED)
 		goto failed;
 
+done:
 	pci_dbg(dev, "broadcast resume message\n");
 	pci_walk_bus(bus, report_resume, &status);