Re: [PATCHv4] x86/sgx: Avoid softlockup from sgx_vepc_release

[Ingo Molnar <mingo@kernel.org>]

* Jack Wang <jinpu.wang@ionos.com> wrote:

> We hit softlocup with following call trace:
> 
> ? asm_sysvec_apic_timer_interrupt+0x16/0x20
> xa_erase+0x21/0xb0
> ? sgx_free_epc_page+0x20/0x50
> sgx_vepc_release+0x75/0x220
> __fput+0x89/0x250
> task_work_run+0x59/0x90
> do_exit+0x337/0x9a0
> 
> Similar like commit 8795359e35bc ("x86/sgx: Silence softlockup detection
> when releasing large enclaves"). The test system has 64GB of enclave memory,
> and all assigned to a single VM. Release vepc take longer time and triggers
> the softlockup warning.
> 
> Add cond_resched() to give other tasks a chance to run and placate
> the softlockup detector.

I've rewritten the changelog: it's not just a change to 'placate' the 
softlockup detector, the SGX code was causing *real*, very long 
non-preemptible delays in the kernel. That's a real kernel bug, not some 
softlockup whingle that needs to be silenced ...

So what this patch does is to break up those delays & latencies, and that 
softlockup doesn't warn anymore is a side effect fix.

I've changed the description accordingly, and applied it to tip:x86/urgent.

Thanks,

	Ingo