On 2024-04-10 at 15:35:39 +0300, Kirill A. Shutemov wrote:
> On Wed, Apr 10, 2024 at 06:23:01PM +0800, Chen Yu wrote:
> > Commit 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused
> > by parallel memory acceptance") has released the spinlock so
> > other CPUs can do memory acceptance in parallel and not
> > triggers softlockup on other CPUs.
> >
> > However the softlock up was intermittent shown up if the memory
> > of the TD guest is large, and the timeout of softlockup is set
> > to 1 second:
> >
> > RIP: 0010:_raw_spin_unlock_irqrestore
> > Call Trace:
> > ? __hrtimer_run_queues
> > <IRQ>
> > ? hrtimer_interrupt
> > ? watchdog_timer_fn
> > ? __sysvec_apic_timer_interrupt
> > ? __pfx_watchdog_timer_fn
> > ? sysvec_apic_timer_interrupt
> > </IRQ>
> > ? __hrtimer_run_queues
> > <TASK>
> > ? hrtimer_interrupt
> > ? asm_sysvec_apic_timer_interrupt
> > ? _raw_spin_unlock_irqrestore
> > ? __sysvec_apic_timer_interrupt
> > ? sysvec_apic_timer_interrupt
> > accept_memory
> > try_to_accept_memory
> > do_huge_pmd_anonymous_page
> > get_page_from_freelist
> > __handle_mm_fault
> > __alloc_pages
> > __folio_alloc
> > ? __tdx_hypercall
> > handle_mm_fault
> > vma_alloc_folio
> > do_user_addr_fault
> > do_huge_pmd_anonymous_page
> > exc_page_fault
> > ? __do_huge_pmd_anonymous_page
> > asm_exc_page_fault
> > __handle_mm_fault
>
> Stacktrace doesn't add much value here. Just drop it.
>
OK, will do.
> > When the local irq is enabled at the end of accept_memory(),
> > the softlockup detects that the watchdog on single CPU has
> > not been fed for a while. That is to say, even other CPUs
> > will not be blocked by spinlock, the current CPU might be
> > stunk with local irq disabled for a while, which hurts not
> > only nmi watchdog but also softlockup.
> >
> > Chao Gao pointed out that the memory accept could be time
> > costly and there was similar report before. Thus to avoid
> > any softlocup detection during this stage, give the
> > softlockup a flag to skip the timeout check at the end of
> > accept_memory(), by invoking touch_softlockup_watchdog().
> >
> > Reported-by: "Hossain, Md Iqbal" <md.iqbal.hossain@xxxxxxxxx>
> > Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>
> And I think it is justified to add Fixes tag:
>
> Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
>
OK, I'll refine the patch and send v2, thanks!
thanks,Chenyu
