Re: [PATCH 0/4] KVM: x86: TIF_NEED_FPU_LOAD bug fixes

Liu, Jing2
2020-03-04T07:38:57Z

On 1/17/2020 2:26 PM, Sean Christopherson wrote:
> TIF_FPU_NEED_LOAD can be set any time
> control is transferred out of KVM, e.g. via IRQ->softirq, not just when
> KVM is preempted.

Hi Sean,

Is this just because kernel_fpu_begin() is called during softirq? I saw
the dump trace in 3/4 message, but didn't find out clue.

Could I ask where kernel_fpu_begin() is called? Or is this just a
"possible" thing?

Because I just want to make sure that, kvm can use this flag to cover
all preempt/softirq/(other?) cases?

Thanks,

Jing