linux-kernel - Re: [PATCH 2/2] cxl/mbox: Wire up irq support

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Message-ID: <63546b48dcd31_141929434@dwillia2-mobl3.amr.corp.intel.com.notmuch>
Date:   Sat, 22 Oct 2022 15:14:32 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Davidlohr Bueso <dave@...olabs.net>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     <dan.j.williams@...el.com>, <ira.weiny@...el.com>,
        <dave.jiang@...el.com>, <alison.schofield@...el.com>,
        <bwidawsk@...nel.org>, <vishal.l.verma@...el.com>,
        <a.manzanares@...sung.com>, <linux-cxl@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] cxl/mbox: Wire up irq support

Davidlohr Bueso wrote:
> On Tue, 18 Oct 2022, Jonathan Cameron wrote:
> 
> >Whilst I get the need for an example, I'd rather this didn't
> >go in until we have that background handler in place.
> 
> One of the reasons why the bg stuff hasn't been re-posted is
> because the only user currently is the sanitation work
> (and hopefully maybe scan media soon), which in turn depends
> on the cache-flushing thing to be picked up (unless someone
> starts ranting again against wbinvd). And that is in Dave's
> pmem security series which I'm hoping will be picked up for
> v6.3 at some point.
> 
> So I guess we're a while away from the irq thing. I was mostly
> suggesting sending an mbox-only just to layout the
> pci_alloc_irq_vectors if we're not using the common table,
> but per the above this might not be sooner than the pmu or
> events stuff...
> 
> >Unused infrastructure tends to rot or not be quite what is
> >needed.
> 
> No arguing there.

I do feel that event notifications are likely the nearest consumer
because the whole reason to do the RCD work is to support OS native
error handling for these CXL 1.1+ devices that people can actually get
their hands on today. Error handling and other RAS flows need to be able
to hear the device's screams for help.