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SubjectRe: [PATCH] Fix resume on x86-32 machines
On Sun 2017-12-10 13:58:23, Andy Lutomirski wrote:
> > On Dec 10, 2017, at 1:38 PM, Pavel Machek <pavel@ucw.cz> wrote:
> >
> >
> > After 4.15-rc2, suspend stopped working on Thinkpad X60. 5b06bbc
> > (unintentionally?) reordered stuff with respect to
> > fix_processor_context() on 32-bit and 64-bit. We undo that change on
> > 32-bit.
> >
>
> Can you explain what was wrong with the reordering? Your patch certainly *looks* incorrect.
>

No, I can't, sorry.

> I'm guessing that the real issue is that 32-bit needs %fs restored
> early for TLS.

Maybe. I can test patches...

I don't think it would be good idea to revert
5b06bbcfc2c621da3009da8decb7511500c293ed, but since it introduced
regression in -rc2, I believe we should fix the regression now, and
then we can try to provide cleaner solution.

As Linus noted, the code is quite "interesting".
Pavel


>
> > While we are at it, fix a comment.
> >
> > Signed-off-by: Pavel Machek <pavel@ucw.cz>
> > Fixes: 5b06bbcfc2c621da3009da8decb7511500c293ed
> >
> > diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
> > index 5191de1..af7b613 100644
> > --- a/arch/x86/power/cpu.c
> > +++ b/arch/x86/power/cpu.c
> > @@ -216,8 +216,8 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
> > write_cr0(ctxt->cr0);
> >
> > /*
> > - * now restore the descriptor tables to their proper values
> > - * ltr is done i fix_processor_context().
> > + * Now restore the descriptor tables to their proper values
> > + * ltr is done in fix_processor_context().
> > */
> > #ifdef CONFIG_X86_32
> > load_idt(&ctxt->idt);
> > @@ -235,13 +235,11 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
> > wrmsrl(MSR_GS_BASE, ctxt->gs_base);
> > #endif
> >
> > - fix_processor_context();
> > -
> > +#ifdef CONFIG_X86_32
> > /*
> > - * Restore segment registers. This happens after restoring the GDT
> > - * and LDT, which happen in fix_processor_context().
> > + * Restore segment registers.
> > */
> > -#ifdef CONFIG_X86_32
> > +
> > loadsegment(es, ctxt->es);
> > loadsegment(fs, ctxt->fs);
> > loadsegment(gs, ctxt->gs);
> > @@ -252,8 +250,17 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
> > */
> > if (boot_cpu_has(X86_FEATURE_SEP))
> > enable_sep_cpu();
> > +
> > + fix_processor_context();
> > #else
> > /* CONFIG_X86_64 */
> > + /*
> > + * Restore segment registers. This happens after restoring the GDT
> > + * and LDT, which happen in fix_processor_context().
> > + */
> > +
> > + fix_processor_context();
> > +
> > asm volatile ("movw %0, %%ds" :: "r" (ctxt->ds));
> > asm volatile ("movw %0, %%es" :: "r" (ctxt->es));
> > asm volatile ("movw %0, %%fs" :: "r" (ctxt->fs));
> >

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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