Re: Unifying x86_64 / Xen init paths and reading hardware_subarch early

From	Borislav Petkov <bp@suse.de>
Newsgroups	linux.kernel
Subject	Re: Unifying x86_64 / Xen init paths and reading hardware_subarch early
Date	2016-01-16 10:20 +0100
Message-ID	<qRvbz-2p8-1@gated-at.bofh.it> (permalink)
References	<qRkJc-3M8-9@gated-at.bofh.it> <qRmhY-4D4-1@gated-at.bofh.it> <qRne4-5ix-65@gated-at.bofh.it> <qRo0r-5P2-31@gated-at.bofh.it>
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On Fri, Jan 15, 2016 at 05:39:05PM -0800, Luis R. Rodriguez wrote:
> On Fri, Jan 15, 2016 at 4:43 PM, Luis R. Rodriguez <mcgrof@suse.com> wrote:
> >>     for (i = 0; i < sizeof(boot_params); i += 4096)
> >>         early_make_pgtable((unsigned long)params + i);
> >
> >  I'll give this a shot.
> 
> Thanks again for this! It seems to let this boot now! But it does not
> seem to provided the right value. If I use the qemu debug patch as I
> listed before to set this to 5 for kvm, and boot it doesn't come up.
> This can be tested with the qemu debug patch + this debug kernel patch
> which prints it out and resets it from what it finds early.
> 
> If you comment out the boot_params.hdr.hardware_subarch =
> my_hardware_subarch; assignment we get the right value from the
> copy_bootdata() work. I use my_hardware_subarch just as a quick hack
> to test and cache the value early code gets but that I can't print
> early on.

You can always do stupid debug loops:

	while (subarch == <expected_value>)
		rep_nop();

and when your guest stops booting and gdb points you here, then you know
what's going on. You can then dump interesting stuff too from gdb.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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Unifying x86_64 / Xen init paths and reading hardware_subarch early "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-01-15 23:10 +0100
  Re: Unifying x86_64 / Xen init paths and reading hardware_subarch early Andy Lutomirski <luto@amacapital.net> - 2016-01-16 00:50 +0100
    Re: Unifying x86_64 / Xen init paths and reading hardware_subarch  early "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-01-16 01:50 +0100
      Re: Unifying x86_64 / Xen init paths and reading hardware_subarch early "H. Peter Anvin" <hpa@zytor.com> - 2016-01-16 02:20 +0100
      Re: Unifying x86_64 / Xen init paths and reading hardware_subarch early "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2016-01-16 02:40 +0100
        Re: Unifying x86_64 / Xen init paths and reading hardware_subarch  early Borislav Petkov <bp@suse.de> - 2016-01-16 10:20 +0100

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