On Thu, 29 Feb 2024 14:05:58 -0800 Brett Creeley <bcreeley@xxxxxxx> wrote: > On 2/29/2024 1:11 AM, Shameer Kolothum wrote: > > Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding. > > > > > > The deferred_reset logic was added to vfio migration drivers to prevent > > a circular locking dependency with respect to mm_lock and state mutex. > > This is mainly because of the copy_to/from_user() functions(which takes > > mm_lock) invoked under state mutex. But for HiSilicon driver, the only > > place where we now hold the state mutex for copy_to_user is during the > > PRE_COPY IOCTL. So for pre_copy, release the lock as soon as we have > > updated the data and perform copy_to_user without state mutex. By this, > > we can get rid of the deferred_reset logic. > > > > Link: https://lore.kernel.org/kvm/20240220132459.GM13330@xxxxxxxxxx/ > > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> > > Shameer, > > Thanks for providing this example. After seeing this, it probably > doens't make sense to accept my 2/2 patch at > https://lore.kernel.org/kvm/20240228003205.47311-3-brett.creeley@xxxxxxx/. > > I have reworked that patch and am currently doing some testing with it > to make sure it's functional. Once I have some results I will send a v3. Darn, somehow this thread snuck by me last week. Currently your series is at the top of my next branch, so I'll just rebase it to 8512ed256334 ("vfio/pds: Always clear the save/restore FDs on reset") to drop your 2/2 and wait for something new relative to the reset logic. Thanks, Alex
