Re: [PATCH 04/18] cxl/region: Validate region mode vs decoder mode

[Dan Williams <dan.j.williams@intel.com>]

Jonathan Cameron wrote:
> On Sun, 05 Feb 2023 17:02:51 -0800
> Dan Williams <dan.j.williams@intel.com> wrote:
> 
> > In preparation for a new region mode, do not, for example, allow
> > 'ram' decoders to be assigned to 'pmem' regions and vice versa.
> > 
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> 
> I guess we aren't support mixed endpoint decoders for now (and
> maybe never..) If we did I'd expect this to have to allow
> mixed with either RAM or PMEM.

Mixed is a bug, or I otherwise can not think of a scenario where it is
valid. The kernel prevents it, but platform firmware can make
that mistake. I think if the kernel ever encounters that and works
around it that will come with a loud TAINT_FIRMWARE_WORKAROUND warning.

> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > ---
> >  drivers/cxl/core/region.c |    6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index c9e7f05caa0f..53d6dbe4de6d 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -1217,6 +1217,12 @@ static int cxl_region_attach(struct cxl_region *cxlr,
> >  	struct cxl_dport *dport;
> >  	int i, rc = -ENXIO;
> >  
> > +	if (cxled->mode != cxlr->mode) {
> > +		dev_dbg(&cxlr->dev, "%s region mode: %d mismatch: %d\n",
> > +			dev_name(&cxled->cxld.dev), cxlr->mode, cxled->mode);
> > +		return -EINVAL;
> > +	}
> > +
> >  	if (cxled->mode == CXL_DECODER_DEAD) {
> >  		dev_dbg(&cxlr->dev, "%s dead\n", dev_name(&cxled->cxld.dev));
> >  		return -ENODEV;
> > 
>