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

On Wed, Jan 18, 2017 at 04:49:58PM +1100, Michael Ellerman wrote:

Gavin Shan [off-list ref] writes:

quoted

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.

quoted

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 <redacted>

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;

quoted

 	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