linux-kernel - Re: [patch 2/9] x86/process: Unify copy_thread

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Date:   Sun, 10 Nov 2019 08:56:50 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Willy Tarreau <w@....eu>, Juergen Gross <jgross@...e.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [patch 2/9] x86/process: Unify copy_thread_tls()

On Sun, Nov 10, 2019 at 4:36 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Sat, 9 Nov 2019, Thomas Gleixner wrote:
> > On Fri, 8 Nov 2019, Andy Lutomirski wrote:
> > > On 11/6/19 11:35 AM, Thomas Gleixner wrote:
> > > > +static inline int copy_io_bitmap(struct task_struct *tsk)
> > > > +{
> > > > + if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
> > > > +         return 0;
> > > > +
> > > > + tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
> > > > +                                     IO_BITMAP_BYTES, GFP_KERNEL);
> > >
> > > tsk->thread.io_bitmap_max = current->thread.io_bitmap_max?
> > >
> > > I realize you inherited this from the code you're refactoring, but it
> > > does seem to be missing.
> >
> > It already got copied with the task struct :)
> >
> > > > +#ifdef CONFIG_X86_64
> > > > + savesegment(gs, p->thread.gsindex);
> > > > + p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase;
> > > > + savesegment(fs, p->thread.fsindex);
> > > > + p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase;
> > > > + savesegment(es, p->thread.es);
> > > > + savesegment(ds, p->thread.ds);
> > > > +#else
> > > > + /* Clear all status flags including IF and set fixed bit. */
> > > > + frame->flags = X86_EFLAGS_FIXED;
> > > > +#endif
> > >
> > > Want to do another commit to make the eflags fixup unconditional?  I'm
> > > wondering if we have a bug.
> >
> > Let me look at that.
>
> 64bit does not have flags in the inactive_task_frame ...
>

Hmm.  One more thing to unify, I guess.

--Andy