[PATCH] powerpc/eeh: Fix wrong flag passed to eeh_unfreeze_pe()

[PATCH] powerpc/eeh: Fix wrong flag passed to eeh_unfreeze_pe()

[Gavin Shan]

In __eeh_clear_pe_frozen_state(), we should pass the flag's value
instead of its address to eeh_unfreeze_pe(). This doesn't introduce
any problems, but the code is just wrong.

This fixes the code by passing flag's value to eeh_unfreeze_pe().

Cc: stable@vger.kernel.org #3.18+
Fixes: 5cfb20b96f6 ("powerpc/eeh: Emulate EEH recovery for VFIO devices")
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/eeh_driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
index d88573b..fa15fa6 100644
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -549,7 +549,7 @@ static void *__eeh_clear_pe_frozen_state(void *data, void *flag)
 	int i, rc = 1;
 
 	for (i = 0; rc && i < 3; i++)
-		rc = eeh_unfreeze_pe(pe, clear_sw_state);
+		rc = eeh_unfreeze_pe(pe, *clear_sw_state);
 
 	/* Stop immediately on any errors */
 	if (rc) {
-- 
2.7.4

Re: [PATCH] powerpc/eeh: Fix wrong flag passed to eeh_unfreeze_pe()

[Michael Ellerman]

Gavin Shan <gwshan@linux.vnet.ibm.com> writes:

> In __eeh_clear_pe_frozen_state(), we should pass the flag's value
> instead of its address to eeh_unfreeze_pe(). This doesn't introduce
> any problems, but the code is just wrong.

It means any caller that passes false, will be getting the wrong
behaviour. eg. I see at least one call in eeh_reset_device() which
passes false to eeh_clear_pe_frozen_state(), which is then passed to
__eeh_clear_pe_frozen_state().

But I guess you're saying that caller doesn't actually see a bug because
of this?

> This fixes the code by passing flag's value to eeh_unfreeze_pe().
>
> Cc: stable@vger.kernel.org #3.18+
> Fixes: 5cfb20b96f6 ("powerpc/eeh: Emulate EEH recovery for VFIO devices")
> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>
> diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
> index d88573b..fa15fa6 100644
> --- a/arch/powerpc/kernel/eeh_driver.c
> +++ b/arch/powerpc/kernel/eeh_driver.c
> @@ -549,7 +549,7 @@ static void *__eeh_clear_pe_frozen_state(void *data, void *flag)

	bool *clear_sw_state = flag;

>  	int i, rc = 1;
>  
>  	for (i = 0; rc && i < 3; i++)
> -		rc = eeh_unfreeze_pe(pe, clear_sw_state);
> +		rc = eeh_unfreeze_pe(pe, *clear_sw_state);


I think it would be better to just do the dereference once:

	bool clear_sw_state = *(bool *)flag;
	int i, rc = 1;

	for (i = 0; rc && i < 3; i++)
		rc = eeh_unfreeze_pe(pe, clear_sw_state);


cheers

Re: [PATCH] powerpc/eeh: Fix wrong flag passed to eeh_unfreeze_pe()

[Gavin Shan]

On Wed, Jan 18, 2017 at 04:49:58PM +1100, Michael Ellerman wrote:
>Gavin Shan <gwshan@linux.vnet.ibm.com> writes:
>
>> In __eeh_clear_pe_frozen_state(), we should pass the flag's value
>> instead of its address to eeh_unfreeze_pe(). This doesn't introduce
>> any problems, but the code is just wrong.
>
>It means any caller that passes false, will be getting the wrong
>behaviour. eg. I see at least one call in eeh_reset_device() which
>passes false to eeh_clear_pe_frozen_state(), which is then passed to
>__eeh_clear_pe_frozen_state().
>

Yes, when __eeh_clear_pe_frozen_state() succeeds on all child PEs, the
isolated flag is cleared. No failure from __eeh_clear_pe_frozen_state()
was observed previously.

>But I guess you're saying that caller doesn't actually see a bug because
>of this?
>

Yes, I'll update the changelog accordingly, to give more details as above.

>> This fixes the code by passing flag's value to eeh_unfreeze_pe().
>>
>> Cc: stable@vger.kernel.org #3.18+
>> Fixes: 5cfb20b96f6 ("powerpc/eeh: Emulate EEH recovery for VFIO devices")
>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>>
>> diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
>> index d88573b..fa15fa6 100644
>> --- a/arch/powerpc/kernel/eeh_driver.c
>> +++ b/arch/powerpc/kernel/eeh_driver.c
>> @@ -549,7 +549,7 @@ static void *__eeh_clear_pe_frozen_state(void *data, void *flag)
>
>	bool *clear_sw_state = flag;
>
>>  	int i, rc = 1;
>>  
>>  	for (i = 0; rc && i < 3; i++)
>> -		rc = eeh_unfreeze_pe(pe, clear_sw_state);
>> +		rc = eeh_unfreeze_pe(pe, *clear_sw_state);
>
>
>I think it would be better to just do the dereference once:
>
>	bool clear_sw_state = *(bool *)flag;
>	int i, rc = 1;
>
>	for (i = 0; rc && i < 3; i++)
>		rc = eeh_unfreeze_pe(pe, clear_sw_state);
>

Thanks, Michael. I'll update in v2.

Thanks,
Gavin