Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly

[Dave Hansen]

On 05/02/2016 02:24 PM, Yu-cheng Yu wrote:
> On Mon, May 02, 2016 at 02:18:17PM -0700, Yu-cheng Yu wrote:
>> > Before Linux gets into copy_fpstate_to_sigframe(),
>> > current->thread.fpu.fpstate_active must be true.
>> > For eagerfpu, fpregs_active() must also be true.
>> > For lazyfpu, once we try to do FSAVE/FXSAVE/XSAVE,
>> > fpregs_active() will become true as well.
>> > 
>> > We should have not based on boot_cpu_has(X86_FEATURE_XSAVES)
>> > at all. 
>> > 
>> > Why don't we make it simple and always copy_fpregs_to_signal_frame()?
>> > Or, only for the lazy case, i.e. !fpregs_active(), we do __copy_to_user().
> For (lazy && not XSAVES) actually!

I think we're off in the weeds here.

Please just send an updated patch for what you want to do here.