On Thu, Feb 16, 2023 at 9:27 AM Jan Beulich <[email protected]> wrote: > > On 16.02.2023 13:22, Tamas K Lengyel wrote: > > On Thu, Feb 16, 2023 at 3:31 AM Jan Beulich <[email protected]> wrote: > >> > >> On 15.02.2023 17:29, Tamas K Lengyel wrote: > >>> On Wed, Feb 15, 2023 at 5:27 AM Jan Beulich <[email protected]> wrote: > >>>> Did you consider the alternative of adjusting the ASSERT() in question > >>>> instead? It could reasonably become > >>>> > >>>> #ifdef CONFIG_MEM_SHARING > >>>> ASSERT(!p2m_is_hostp2m(p2m) || !remove_root || > >>> !atomic_read(&d->shr_pages)); > >>>> #endif > >>>> > >>>> now, I think. That would be less intrusive a change (helpful for > >>>> backporting), but there may be other (so far unnamed) benefits of > > pulling > >>>> ahead the shared memory teardown. > >>> > >>> I have a hard time understanding this proposed ASSERT. > >> > >> It accounts for the various ways p2m_teardown() can (now) be called, > >> limiting the actual check for no remaining shared pages to the last > >> of all these invocations (on the host p2m with remove_root=true). > >> > >> Maybe > >> > >> /* Limit the check to the final invocation. */ > >> if ( p2m_is_hostp2m(p2m) && remove_root ) > >> ASSERT(!atomic_read(&d->shr_pages)); > >> > >> would make this easier to follow? Another option might be to move > >> the assertion to paging_final_teardown(), ahead of that specific call > >> to p2m_teardown(). > > > > AFAICT d->shr_pages would still be more then 0 when this is called before > > sharing is torn down so the rearrangement is necessary even if we do this > > assert only on the final invocation. I did a printk in place of this assert > > without the rearrangement and afaict it was always != 0. > > Was your printk() in an if() as above? paging_final_teardown() runs really > late during cleanup (when we're about to free struct domain), so I would > be somewhat concerned if by that time the count was still non-zero.
Just replaced the assert with a printk. Without calling relinquish shared pages I don't find it odd that the count is non-zero, it only gets decremented when you do call relinquish. Once the order is corrected it is zero. Tamas
