Re: [PATCH v2] dmaengine: idxd: avoid deadlock in process_misc_interrupts()

[Dave Jiang]

On 8/23/2022 5:54 PM, Jerry Snitselaar wrote:
> On Tue, Aug 23, 2022 at 09:46:19AM -0700, Dave Jiang wrote:
> > On 8/23/2022 9:37 AM, Jerry Snitselaar wrote:
> > > idxd_device_clear_state() now grabs the idxd->dev_lock
> > > itself, so don't grab the lock prior to calling it.
> > >
> > > This was seen in testing after dmar fault occurred on system,
> > > resulting in lockup stack traces.
> > >
> > > Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> > > Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> > > Cc: Vinod Koul <vkoul@xxxxxxxxxx>
> > > Cc: dmaengine@xxxxxxxxxxxxxxx
> > > Fixes: cf4ac3fef338 ("dmaengine: idxd: fix lockdep warning on device driver removal")
> > > Signed-off-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
> > Thanks Jerry!
> >
> > Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> I noticed another problem while looking at this. When the device ends
> up in the halted state, and needs an flr or system reset, it calls
> idxd_wqs_unmap_portal(). Then if you do a modprobe -r idxd, you hit
> the WARN_ON in devm_iounmap(), because the remove code path calls
> idxd_wq_portal_unmap(), and wq->portal is null. I'm not sure if it
> just needs a simple sanity check in drv_disable_wq() to avoid the call
> in the case that it has already been unmapped, or if more cleanup
> needs to be done, and possibly a state to differentiate between
> halted + soft reset possible, versus halted + flr or system reset
> needed.  You get multiple "Device is HALTED" messages during the
> removal as well.

Thanks!

Fenghua, can you please take a look at this when you have a chance? 
Thank you!


> Regards,
> Jerry