Re: [RFC PATCH 04/10 v2 ] x86/fpu: eager switch PKRU state

[Rik van Riel]

On Tue, 2018-09-18 at 18:04 +0200, Sebastian Andrzej Siewior wrote:
> On 2018-09-18 17:29:52 [+0200], Paolo Bonzini wrote:
> > > I don't think it matters what the PKRU state is
> > > for kernel threads, since kernel PTEs should not
> > > be using protection keys anyway.
> > 
> > What about copy_from/to_user?
> 
> This doesn't work for a kernel thread, does it? I mean they share the
> init's MM and never do copy_{from|to}_user.

Indeed, copy_from/to_user only works if current->mm
points at an mm_struct with userspace memory.

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