[PATCH] mei: discard messages from not connected client during power down.

[PATCH] mei: discard messages from not connected client during power down.

[Martin Peres]

From: Alexander Usyskin <alexander.usyskin@intel.com>

This fixes regression introduced by
commit 8d52af6795c0 ("mei: speed up the power down flow")

In power down or suspend flow a message can still be received
from the FW because the clients fake disconnection.
In normal case we interpret messages w/o destination as corrupted
and link reset is performed in order to clean the channel,
but during power down link reset is already in progress resulting
in endless loop. To resolve the issue under power down flow we
discard messages silently.

Cc: <stable@vger.kernel.org> 4.16+
Fixes: 8d52af6795c0 ("mei: speed up the power down flow")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199541
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
 drivers/misc/mei/interrupt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/mei/interrupt.c b/drivers/misc/mei/interrupt.c
index b0b8f18a85e3..6649f0d56d2f 100644
--- a/drivers/misc/mei/interrupt.c
+++ b/drivers/misc/mei/interrupt.c
@@ -310,8 +310,11 @@ int mei_irq_read_handler(struct mei_device *dev,
 	if (&cl->link == &dev->file_list) {
 		/* A message for not connected fixed address clients
 		 * should be silently discarded
+		 * On power down client may be force cleaned,
+		 * silently discard such messages
 		 */
-		if (hdr_is_fixed(mei_hdr)) {
+		if (hdr_is_fixed(mei_hdr) ||
+		    dev->dev_state == MEI_DEV_POWER_DOWN) {
 			mei_irq_discard_msg(dev, mei_hdr);
 			ret = 0;
 			goto reset_slots;
-- 
2.16.2

Re: [PATCH] mei: discard messages from not connected client during power down.

[Greg KH]

On Tue, May 29, 2018 at 11:56:16AM +0300, Martin Peres wrote:
> From: Alexander Usyskin <alexander.usyskin@intel.com>
> 
> This fixes regression introduced by
> commit 8d52af6795c0 ("mei: speed up the power down flow")
> 
> In power down or suspend flow a message can still be received
> from the FW because the clients fake disconnection.
> In normal case we interpret messages w/o destination as corrupted
> and link reset is performed in order to clean the channel,
> but during power down link reset is already in progress resulting
> in endless loop. To resolve the issue under power down flow we
> discard messages silently.
> 
> Cc: <stable@vger.kernel.org> 4.16+
> Fixes: 8d52af6795c0 ("mei: speed up the power down flow")
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199541
> Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
> ---
>  drivers/misc/mei/interrupt.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

Shouldn't this patch go through the char/misc maintainer?

confused,

greg k-h

Re: [PATCH] mei: discard messages from not connected client during power down.

[Martin Peres]

On 29/05/18 12:04, Greg KH wrote:
> On Tue, May 29, 2018 at 11:56:16AM +0300, Martin Peres wrote:
>> From: Alexander Usyskin <alexander.usyskin@intel.com>
>>
>> This fixes regression introduced by
>> commit 8d52af6795c0 ("mei: speed up the power down flow")
>>
>> In power down or suspend flow a message can still be received
>> from the FW because the clients fake disconnection.
>> In normal case we interpret messages w/o destination as corrupted
>> and link reset is performed in order to clean the channel,
>> but during power down link reset is already in progress resulting
>> in endless loop. To resolve the issue under power down flow we
>> discard messages silently.
>>
>> Cc: <stable@vger.kernel.org> 4.16+
>> Fixes: 8d52af6795c0 ("mei: speed up the power down flow")
>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199541
>> Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
>> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
>> ---
>>  drivers/misc/mei/interrupt.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> Shouldn't this patch go through the char/misc maintainer?
> 
> confused,

Sorry for the confusion. I actually tried to avoid this situation by not
Cc:ing everyone, but git send-email did not prompt me to validate the
final email after setting some of the --no-*-cc. Next time, I'll add
--dry-run just to be sure...

Anyway, what I was trying to do is submit this patch to our CI system
since we were the ones reporting the bug. If successful, we will then
apply this patch as a temporary workaround (our core-for-CI branch) to
gather better statistics (reproducing rate is ~5% of our CI runs), and
allow it to land upstream. We'll then drop our workaround when upstream
with the fix gets backmerged in drm-tip.

Sorry again for the noise!

Martin