linux-kernel - Re: [PATCH v4 1/2] x86/mce: Check for writes ignored in MCA

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Date:   Thu, 21 Apr 2022 12:10:07 -0700
From:   Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH v4 1/2] x86/mce: Check for writes ignored in MCA_STATUS
 register

On 4/20/2022 2:17 AM, Borislav Petkov wrote:
> On Mon, Apr 18, 2022 at 08:24:35PM -0700, Smita Koralahalli wrote:
>> Why are we checking this here? This flag (hw_injection_possible)
>> is set to false inside prepare_msrs() called from
>> smp_call_function_single().
>> Should this check be done after the call to smp_call_function_single()?
> Why would you do that then?
>
> Is any of the code after
>
>          if (inj_type == SW_INJ) {
>                  mce_log(m);
>                  return 0;
>          }
>
> worth running if hardware injection is not possible?

Okay I got the gist of this now. This will be mainly useful for subsequent
hardware error injections.

Also, should we move this slightly before? In inj_bank_set() after we check
for sw injection and before reading IPID value?

>
>> Also, we already have inj_desc.err which returns error code to userspace
>> when WRIG in status registers. Why is this flag needed?
> To not do unnecessary work when you *know* hardware injection won't
> work.
>
> :-)

Okay.

>
> Btw, please trim your mails when you reply, just like I did.

I'm sorry. Noted for my next replies!

Thanks,
Smita
>
> Thx.
>