efi/unaccepted: touch soft lockup during memory accept

In the Linux kernel, the following vulnerability has been resolved:

efi/unaccepted: touch soft lockup during memory accept

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

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().