Re: [Xen-devel] [PATCH v4 3/4] x86: fix indirect thunk usage of CONFIG_INDIRECT_THUNK

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Feb 20, 2018 at 05:53:08AM -0700, Jan Beulich wrote:
> >>> On 20.02.18 at 13:42, <roger.pau@xxxxxxxxxx> wrote:
> > On Tue, Feb 20, 2018 at 05:32:17AM -0700, Jan Beulich wrote:
> >> >>> On 20.02.18 at 12:22, <roger.pau@xxxxxxxxxx> wrote:
> >> > On Tue, Feb 20, 2018 at 04:13:42AM -0700, Jan Beulich wrote:
> >> >> >>> On 20.02.18 at 12:01, <roger.pau@xxxxxxxxxx> wrote:
> >> >> > --- a/xen/include/asm-x86/asm_defns.h
> >> >> > +++ b/xen/include/asm-x86/asm_defns.h
> >> >> > @@ -15,6 +15,9 @@
> >> >> >  #include <asm/alternative.h>
> >> >> > 
> >> >> >  #ifdef __ASSEMBLY__
> >> >> > +#ifndef CONFIG_INDIRECT_THUNK
> >> >> > +.equ CONFIG_INDIRECT_THUNK, 0
> >> >> > +#endif
> >> >> >  # include <asm/indirect_thunk_asm.h>
> >> >> >  #else
> >> >> >  asm ( "\t.equ CONFIG_INDIRECT_THUNK, "
> >> >> > 
> >> >> > It's fairly similar to my first approach, but at least "#ifdef
> >> >> > CONFIG_INDIRECT_THUNK" will still work as expected after this fix.
> >> >> 
> >> >> I've used something similar in backports to old versions, so I
> >> >> wonder whether what you quote above is right: Assembly files
> >> >> don't get handed to clang anyway iirc, so the change would
> >> >> seem to be needed in the #else part of the conditional.
> >> > 
> >> > Assembly files do get handed to clang, from xen/Rules.mk:
> >> > 
> >> > %.o: %.S Makefile
> >> >  $(CC) $(AFLAGS) -c $< -o $@
> >> > 
> >> > Xen doesn't call as directly to compile those, or am I missing
> >> > something?
> >> 
> >> Oh, I was referring to the -mno-integrated-as (or whatever it's
> >> called) option. "Handed to clang" wasn't the best way to put it,
> >> I agree. But it's clang's integrated assembler which the problem
> >> is with.
> > 
> > Oh, I see. You are right, this is just a preparatory change for patch
> > 4, which does enable clang's integrated assembler if the right
> > features are present.
> > 
> > Let me know if you think the above chunk is acceptable.
> 
> It is certainly acceptable if it helps; you now apparently agreeing
> I'm more confused though by this question. Iirc you don't enable
> the integrated assembler for assembly sources, but only for C ones.

So at this point the integrated assembler is only enabled for C
sources.

In patch 4 I enable the integrated assembler for everything if
possible, but in order to enable it I need to solve this issue
first. I can merge patches 3 and 4 if it's going to be clearer.

Hope this help shed some light.

Thanks, Roger.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel