[MODERATED] Re: [patch 07/11] [PATCH v2 07/10] Linux Patch #7

[Borislav Petkov <bp@suse.de>]

On Thu, Apr 19, 2018 at 10:25:47PM -0400, speck for konrad.wilk_at_oracle.com wrote:
> x86/cpu: Add fix_this_cpu to be called _after_ check_bugs and at BSP.
> 
> We do a lot of things in the check_bugs() - one of the first
> things we do is identify_boot_cpu() which calls identify_cpu()
> which calls this_cpu->init.
> 
> Once identify_boot_cpu() is done _then_ it walks through the
> spectre_v2_select_mitigation() and alternative_assembler().
> 
> If there are some CPU fix ups _after_ spectre_v2 is done
> we can't activate those on the BSP as we have already
> called 'this_cpu->init'. Hence add a new function to
> fixup CPUs.

Konrad, this is still unnecessary and adding superfluous complexity to
an already crazy early boot path. Let me clarify the flow:

First you are on the BSP:

setup_arch()
|-> early_cpu_init
|-> early_identify_cpu
|-> cpu_set_bug_bits

now you have all the X86_BUG bits set so that you can test them in the
functions later.

Then, you're still on the BSP and can do check_bugs() with all cmdline
options picking apart etc etc.

setup_arch()
|-> check_bugs()
|-> ssb_select_mitigation()
|-> identify_boot_cpu()			<--- HERE you call ->c_init() on the BSP
|-> spectre_v2_select_mitigation

In that order!

So, all you wanna do works without adding this new function pointer.

-- 
Regards/Gruss,
    Boris.

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