Re: [PATCH v2 2/5] x86/mce/inject: Warn the user on a not set valid bit in MCA_STATUS

[Koralahalli Channabasappa, Smita]

Hi Boris,

On 10/26/21 5:02 AM, Borislav Petkov wrote:

> On Tue, Oct 19, 2021 at 06:36:38PM -0500, Smita Koralahalli wrote:
> > MCA handlers check the valid bit in each status register (MCA_STATUS[Val])
> > and will likely ignore signatures if the valid bit is not set.
> >
> > Warn the user if the valid bit is not set before doing error injection.
> >
> > Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
> > ---
> > v2:
> > 	Added a warning statement instead of setting the valid bit.
> > ---
> >   arch/x86/kernel/cpu/mce/inject.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
> > index 601efd104bb4..a993dc3d0333 100644
> > --- a/arch/x86/kernel/cpu/mce/inject.c
> > +++ b/arch/x86/kernel/cpu/mce/inject.c
> > @@ -487,6 +487,9 @@ static void do_inject(void)
> >   
> >   	i_mce.tsc = rdtsc_ordered();
> >   
> > +	if (!(i_mce.status & MCI_STATUS_VAL))
> > +		pr_warn("Handlers might ignore signatures with Val=0 in MCA_STATUS\n");
> > +
> >   	if (i_mce.misc)
> >   		i_mce.status |= MCI_STATUS_MISCV;
> >   
> > --
> So what's the real reason for this?
>
> You've injected and you didn't get any feedback and were wondering why?
>
> If handlers ignore !VAL MCEs, why don't you simply set it
> unconditionally on entry to do_inject()?

Like how it was done here?
https://lkml.kernel.org/r/20210915232739.6367-3-Smita.KoralahalliChannabasappa@xxxxxxx

Thanks,