Re: [PATCH v6 3/4] x86/mce: Handle AMD threshold interrupt storms

[Yazen Ghannam]

On 6/23/2023 10:45 AM, Borislav Petkov wrote:
> On Fri, Jun 16, 2023 at 11:27:43AM -0700, Tony Luck wrote:
> > +static void _reset_block(struct threshold_block *block)
> > +{
> > +	struct thresh_restart tr;
> > +
> > +	memset(&tr, 0, sizeof(tr));
> > +	tr.b = block;
> > +	threshold_restart_bank(&tr);
> > +}
>
> > +
> > +static void toggle_interrupt_reset_block(struct threshold_block *block, bool on)
> > +{
> > +	if (!block)
> > +		return;
> > +
> > +	block->interrupt_enable = !!on;
> > +	_reset_block(block);
> > +}
> > +
> > +void mce_amd_handle_storm(int bank, bool on)
> > +{
> > +	struct threshold_block *first_block = NULL, *block = NULL, *tmp = NULL;
> > +	struct threshold_bank **bp = this_cpu_read(threshold_banks);
> > +	unsigned long flags;
> > +
> > +	if (!bp)
> > +		return;
> > +
> > +	local_irq_save(flags);
> > +
> > +	first_block = bp[bank]->blocks;
> > +	if (!first_block)
> > +		goto end;
> > +
> > +	toggle_interrupt_reset_block(first_block, on);
> > +
> > +	list_for_each_entry_safe(block, tmp, &first_block->miscj, miscj)
> > +		toggle_interrupt_reset_block(block, on);
> > +end:
> > +	local_irq_restore(flags);
> > +}
>
> There's already other code which does this threshold block control. Pls
> refactor and unify it instead of adding almost redundant similar functions.

Okay, will do.

> >   static void mce_threshold_block_init(struct threshold_block *b, int offset)
> >   {
> >   	struct thresh_restart tr = {
> > @@ -868,6 +909,7 @@ static void amd_threshold_interrupt(void)
> >   	struct threshold_block *first_block = NULL, *block = NULL, *tmp = NULL;
> >   	struct threshold_bank **bp = this_cpu_read(threshold_banks);
> >   	unsigned int bank, cpu = smp_processor_id();
> > +	u64 status;
> >   
> >   	/*
> >   	 * Validate that the threshold bank has been initialized already. The
> > @@ -881,6 +923,13 @@ static void amd_threshold_interrupt(void)
> >   		if (!(per_cpu(bank_map, cpu) & BIT_ULL(bank)))
> >   			continue;
> >   
> > +		rdmsrl(mca_msr_reg(bank, MCA_STATUS), status);
> > +		track_cmci_storm(bank, status);
>
> So this is called from interrupt context.
>
> There's another track_cmci_storm() from machine_check_poll() which can
> happen in process context.
>
> And there's no sync (locking) between the two. Not good.
>
> Why are even two calls needed on AMD?

I think because the AMD interrupt handlers don't call 
machine_check_poll(). This is a good opportunity to unify the AMD 
thresholding and deferred error interrupt handlers with 
machine_check_poll().

Tony,
Please leave out this AMD patch for now. I'll work on refactoring it.

Thanks,
Yazen