Messages in this thread | | | Date | Tue, 5 Feb 2019 19:16:01 +0100 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH 08/22] x86/fpu: Remove user_fpu_begin() |
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On 2019-01-25 16:18:40 [+0100], Borislav Petkov wrote: > Reviewed-by: Borislav Petkov <bp@suse.de> thanks.
> Should we do this microoptimization in addition, to save us the > activation when the kernel thread here: > > taskA -> kernel thread -> taskA > > doesn't call kernel_fpu_begin() and thus fpu_fpregs_owner_ctx remains > the same?
This might work now but at the end of the series this case will be handled. The switch taskA -> kernel thread
will save taskA's registers. The switch kernel thread -> taskA
will only set TF flag to restore FPU registers on the return to userland. The load happens only the ctx pointer is different.
> It would be a bit more correct as it won't invoke the > trace_x86_fpu_regs_activated() TP in case the FPU context is the same.
The trace point is not wrong. As of now the same context will be loaded again.
Sebastian
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