linux-kernel - Re: [RFC PATCH 9/9] cxl/pci: Enable interrupts for CXL PCIe ports' AER internal errors

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Date: Tue, 2 Jul 2024 17:00:03 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Terry Bowman <Terry.Bowman@....com>
CC: <dan.j.williams@...el.com>, <ira.weiny@...el.com>, <dave@...olabs.net>,
	<dave.jiang@...el.com>, <alison.schofield@...el.com>, <ming4.li@...el.com>,
	<vishal.l.verma@...el.com>, <jim.harris@...sung.com>,
	<ilpo.jarvinen@...ux.intel.com>, <ardb@...nel.org>,
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Yazen.Ghannam@....com>,
	<Robert.Richter@....com>
Subject: Re: [RFC PATCH 9/9] cxl/pci: Enable interrupts for CXL PCIe ports'
 AER internal errors

On Mon, 24 Jun 2024 11:46:01 -0500
Terry Bowman <Terry.Bowman@....com> wrote:

> Hi Jonathan,
> 
> I added responses inline below.
> 
> On 6/20/24 08:15, Jonathan Cameron wrote:
> > On Mon, 17 Jun 2024 15:04:11 -0500
> > Terry Bowman <terry.bowman@....com> wrote:
> >   
> >> CXL RAS errors are reported through AER interrupts using the AER status:
> >> correctbale internal errors (CIE) and AER uncorrectable internal errors  
> > 
> > correctable
> >   
> 
> Thanks.
> 
> >> (UIE).[1] But, the AER CIE/UIE are disabled by default preventing
> >> notification of CXL RAS errors.[2]
> >>
> >> Enable CXL PCIe port RAS notification by unmasking the ports' AER CIE
> >> and UIE errors.
> >>
> >> [1] CXL3.1 - 12.2.2 CXL Root Ports, Downstream Switch Ports, and Upstream
> >>              Switch Ports
> >> [2] PCI6.0 - 7.8.4.3 Uncorrectable Error Mask Register (Offset 08h),
> >>              7.8.4.6 Correctable Error Mask Register (Offset 14h)
> >>
> >> Signed-off-by: Terry Bowman <terry.bowman@....com>  
> > 
> > I'm not sure doing this from a driver other than the one handling the
> > errors makes sense.  It is doing a couple of RMW without any locking
> > or guarantees that the driver bound to the PCI port might care about
> > this changing.
> >   
> 
> I think this could fit into the helper function mentioned in our earlier 
> discussion. When the portdrv's notifier enabler is called it could also
> enable the UIE/CIE.
> 
> > I'd like more info on why we don't just turn this on in general
> > and hence avoid the need to control it from the 'wrong' place.
> > 
> > Jonathan
> >   
> 
> I was trying to enable only where needed given the one case is not a 
> pattern, yet. At this point it is only for CXL RCH downstream port 
> and CXL VH ports (portdrv).
> 
> Would you like for the UIE/CIE unmask added to the AER driver init ?

If we can get away with it, yes!