Re: [PATCH v2 06/16] x86/mce: Remove __mcheck_cpu_init_early()

[Yazen Ghannam <yazen.ghannam@amd.com>]

On Thu, Feb 27, 2025 at 09:48:01PM +0100, Borislav Petkov wrote:
> On February 27, 2025 8:59:33 PM GMT+01:00, Yazen Ghannam <yazen.ghannam@amd.com> wrote:
> >On Thu, Feb 27, 2025 at 08:33:19PM +0100, Borislav Petkov wrote:
> >> On February 27, 2025 5:31:48 PM GMT+01:00, Yazen Ghannam <yazen.ghannam@amd.com> wrote:
> >> >On Thu, Feb 27, 2025 at 04:25:00PM +0100, Borislav Petkov wrote:
> >> >> On Thu, Feb 13, 2025 at 04:45:55PM +0000, Yazen Ghannam wrote:
> >> >> > Also, move __mcheck_cpu_init_generic() after
> >> >> > __mcheck_cpu_init_prepare_banks() so that MCA is enabled after the first
> >> >> > MCA polling event.
> >> >> 
> >> >> The reason being?
> >> >> 
> >> >> Precaution?
> >> >> 
> >> >> It was this way since forever, why are you moving it now? Any particular
> >> >> reason?
> >> >> 
> >> >
> >> >1) To read/clear old errors before turning on MCA. The updated
> >> >__mcheck_cpu_init_prepare_banks() function does this for the MCi_CTL
> >> >registers. This patch does this for the MCG_CTL register too.
> >> >
> >> >2) To ensure that vendor-specific setup is finished beforehand also.
> >> 
> >> That doesn't answer my question. All of the above gets done even without shuffling the order...
> >> 
> >> 
> >
> >MCA banks can start logging errors once MCG_CTL is set. The AMD docs say
> >"The operating system must initialize the MCA_CONFIG registers prior to
> >initialization of the MCA_CTL registers."
> >
> >"The MCA_CTL registers must be initialized prior to enabling the error
> >reporting banks in MCG_CTL".
> >
> >However, the Intel docs "Machine-Check Initialization Pseudocode" say
> >MCG_CTL first then MCi_CTL.
> >
> >But both agree that CR4.MCE should be set last.
> >
> >We have an old thread on the topic that led to this patch.
> >https://lore.kernel.org/all/YqJHwXkg3Ny9fI3s@yaz-fattaah/
> >
> >And it seemed okay at the time.
> >https://lore.kernel.org/all/YrnTMmwl5TrHwT9J@zn.tnic/
> >
> >I don't think anything much has changed since then, so I included the
> >old patch again in this set.
> >
> >Thanks,
> >Yazen
> 
> This is exactly what needs to be in the commit message - why is the change being done. 
> -- 

Sure thing. I'll update the commit message.

Thanks,
Yazen