On Tue, 7 Jan 2025 12:41:46 -0700
Dave Jiang <dave.jiang@xxxxxxxxx> wrote:
> On 12/24/24 5:11 AM, Jonathan Cameron wrote:
> > On Wed, 4 Dec 2024 15:46:48 -0700
> > Dave Jiang <dave.jiang@xxxxxxxxx> wrote:
> >
> >> Add the aliased address of extended linear cache when emitting event
> >> trace for DRAM and general media of CXL events.
> >>
> >> Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> > I wonder if you want to future proof the hpa_alias for potential case
> > of there being more than 1? hpa_alias0 or similar so that we can add
> > more as needed?
>
> Do you mean when emitting via the trace? Yeah I can change it to hpa_alias0 in the output string.
>
err. Can't entirely remember what I meant but that seems sensible ;)
>
> >
> >
> > Otherwise, looks like there is either a null point dereference or
> > overly paranoid existing code. I haven't checked which but changes
> > needed either way.
>
> I'll move it under the if (cxlr) and also add a check for cxlr in the helper function.
>
> DJ
>
>
> >
> > Jonathan
> >
> >> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> >> index 5175138c4fb7..4017b7afa78a 100644
> >> --- a/drivers/cxl/core/mbox.c
> >> +++ b/drivers/cxl/core/mbox.c
> >> @@ -856,6 +856,24 @@ int cxl_enumerate_cmds(struct cxl_memdev_state *mds)
> >> }
> >> EXPORT_SYMBOL_NS_GPL(cxl_enumerate_cmds, CXL);
> >>
> >> +static u64 cxlr_hpa_cache_alias(struct cxl_region *cxlr, u64 hpa)
> >> +{
> >> + struct cxl_region_params *p = &cxlr->params;
> >
> > Bad idea to unconditionally dereference I think. See below.
> >
> >> + int nid;
> >> +
> >> + if (!p->cache_size)
> >> + return ~0ULL;
> >> +
> >> + nid = cxl_region_nid(cxlr);
> >> + if (nid == NUMA_NO_NODE)
> >> + nid = 0;
> >> +
> >> + if (hpa >= p->res->start + p->cache_size)
> >> + return hpa - p->cache_size;
> >> +
> >> + return hpa + p->cache_size;
> >> +}
> >> +
> >> void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
> >> enum cxl_event_log_type type,
> >> enum cxl_event_type event_type,
> >> @@ -871,7 +889,7 @@ void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
> >> }
> >>
> >> if (trace_cxl_general_media_enabled() || trace_cxl_dram_enabled()) {
> >> - u64 dpa, hpa = ULLONG_MAX;
> >> + u64 dpa, hpa = ULLONG_MAX, hpa_alias;
> >> struct cxl_region *cxlr;
> >>
> >> /*
> >> @@ -887,11 +905,14 @@ void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
> >> if (cxlr)
> >> hpa = cxl_dpa_to_hpa(cxlr, cxlmd, dpa);
> >>
> >> + hpa_alias = cxlr_hpa_cache_alias(cxlr, hpa);
> >
> > If there is no region, and hence no hpa does it make sense to call this?
> > Particularly as first thing done in this is to dereference cxlr.
> >
> >
> >> +
> >> if (event_type == CXL_CPER_EVENT_GEN_MEDIA)
> >> trace_cxl_general_media(cxlmd, type, cxlr, hpa,
> >> - &evt->gen_media);
> >> + hpa_alias, &evt->gen_media);
> >> else if (event_type == CXL_CPER_EVENT_DRAM)
> >> - trace_cxl_dram(cxlmd, type, cxlr, hpa, &evt->dram);
> >> + trace_cxl_dram(cxlmd, type, cxlr, hpa, hpa_alias,
> >> + &evt->dram);
> >> }
> >> }
> >> EXPORT_SYMBOL_NS_GPL(cxl_event_trace_record, CXL);
> >
>
>
