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.
> 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")
--
Kiryl Shutsemau / Kirill A. Shutemov
