linux-kernel - Re: [PATCH 4/5] resource: Report parent to walk_iomem_res

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Message-ID: <CAPcyv4goRP8EAfMX8oOANgzgm3Pn=wES42MCDXbP_x__-GW52g@mail.gmail.com>
Date:   Tue, 17 Mar 2020 15:04:48 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Wei Yang <richardw.yang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] resource: Report parent to walk_iomem_res_desc() callback

On Thu, Mar 5, 2020 at 6:42 AM Tom Lendacky <thomas.lendacky@....com> wrote:
>
> On 3/2/20 4:20 PM, Dan Williams wrote:
> > In support of detecting whether a resource might have been been claimed,
> > report the parent to the walk_iomem_res_desc() callback. For example,
> > the ACPI HMAT parser publishes "hmem" platform devices per target range.
> > However, if the HMAT is disabled / missing a fallback driver can attach
> > devices to the raw memory ranges as a fallback if it sees unclaimed /
> > orphan "Soft Reserved" resources in the resource tree.
> >
> > Otherwise, find_next_iomem_res() returns a resource with garbage data
> > from the stack allocation in __walk_iomem_res_desc() for the res->parent
> > field.
>
> Just wondering if we shouldn't just copy the complete resource struct and
> just override the start and end values? That way, if some code in the
> future wants to look at sibling or child values, another change isn't needed.
>
> Just a thought.

Thanks for taking a look. I think it's ok to come update this again if
that need arises.