linux-kernel - Re: [RFC PATCH] resource: Fix CXL node not populated issue

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Message-ID: <de22dd6e-00a3-4183-a123-15cc7c53980f@amd.com>
Date: Wed, 11 Dec 2024 12:10:14 +0530
From: Bharata B Rao <bharata@....com>
To: Dan Williams <dan.j.williams@...el.com>,
 Raghavendra K T <raghavendra.kt@....com>, linux-kernel@...r.kernel.org,
 linux-cxl@...r.kernel.org
Cc: Huang Ying <ying.huang@...el.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>, Davidlohr Bueso <dave@...olabs.net>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Dave Jiang <dave.jiang@...el.com>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Alistair Popple <apopple@...dia.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Bjorn Helgaas <bhelgaas@...gle.com>, Baoquan He <bhe@...hat.com>,
 ilpo.jarvinen@...ux.intel.com,
 Mika Westerberg <mika.westerberg@...ux.intel.com>,
 Fontenot Nathan <Nathan.Fontenot@....com>, Wei Huang <wei.huang2@....com>,
 regressions@...ts.linux.dev
Subject: Re: [RFC PATCH] resource: Fix CXL node not populated issue

On 11-Dec-24 10:14 AM, Dan Williams wrote:
> 
> I was able to reproduce a similar set of conditions with the cxl_test
> environment:
> 
> f010000000-f04fffffff : Soft Reserved
>    f010000000-f04fffffff : CXL Window 0
>      f020000000-f03fffffff : region3
>        f020000000-f03fffffff : dax3.0
>          f020000000-f03fffffff : System RAM (kmem)
> 
> 
> ...but that did not result in the bug. So there are some other details
> missing. Can you proceed with providing the dmesg from the good and the
> bad cases?
> 
> gist.github.com is useful for this.

Sorry for the delay in providing the data. The system wasn't available 
for a while. Now I have put the good(6.11.0-rc6) and bad(6.13.0-rc1) 
dmesg and iomem logs at

https://gist.github.com/bharata/4a57db11e044fd1d313035f3dd5f763b

What I see is that in the bad case, we hit the below shown dev_dbg 
message (not seen in the logs that are provided)

static int hmem_register_device(struct device *host, int target_nid,
                                 const struct resource *res)
{
         struct platform_device *pdev;
         struct memregion_info info;
         long id;
         int rc;

         if (IS_ENABLED(CONFIG_CXL_REGION) &&
             region_intersects(res->start, resource_size(res), 
IORESOURCE_MEM,
                               IORES_DESC_CXL) != REGION_DISJOINT) {
                 dev_dbg(host, "deferring range to CXL: %pr\n", res); <--
                 return 0;
         }

With this, it appears that dev_dax_kmem_probe() won't happen for the CXL 
range and hence CXL memory doesn't get detected.

Let us know if you need more debug data.

Regards,
Bharata.