linux-kernel - Re: [PATCH 2/5] mm/resource: move HMM pr

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Date:   Tue, 29 Jan 2019 12:34:50 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Dave Hansen <dave.hansen@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Jiang <dave.jiang@...el.com>, zwisler@...nel.org,
        vishal.l.verma@...el.com, thomas.lendacky@....com,
        Andrew Morton <akpm@...ux-foundation.org>, mhocko@...e.com,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
        Huang Ying <ying.huang@...el.com>,
        Wu Fengguang <fengguang.wu@...el.com>,
        Jerome Glisse <jglisse@...hat.com>
Subject: Re: [PATCH 2/5] mm/resource: move HMM pr_debug() deeper into resource code

Dave Hansen <dave.hansen@...el.com> writes:
> On 1/25/19 1:18 PM, Bjorn Helgaas wrote:
>> On Thu, Jan 24, 2019 at 5:21 PM Dave Hansen <dave.hansen@...ux.intel.com> wrote:
>>> diff -puN kernel/resource.c~move-request_region-check kernel/resource.c
>>> --- a/kernel/resource.c~move-request_region-check       2019-01-24 15:13:14.453199539 -0800
>>> +++ b/kernel/resource.c 2019-01-24 15:13:14.458199539 -0800
>>> @@ -1123,6 +1123,16 @@ struct resource * __request_region(struc
>>>                 conflict = __request_resource(parent, res);
>>>                 if (!conflict)
>>>                         break;
>>> +               /*
>>> +                * mm/hmm.c reserves physical addresses which then
>>> +                * become unavailable to other users.  Conflicts are
>>> +                * not expected.  Be verbose if one is encountered.
>>> +                */
>>> +               if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
>>> +                       pr_debug("Resource conflict with unaddressable "
>>> +                                "device memory at %#010llx !\n",
>>> +                                (unsigned long long)start);
>> 
>> I don't object to the change, but are you really OK with this being a
>> pr_debug() message that is only emitted when enabled via either the
>> dynamic debug mechanism or DEBUG being defined?  From the comments, it
>> seems more like a KERN_INFO sort of message.
>
> I left it consistent with the original message that was in the code.
> I'm happy to change it, though, if the consumers of it (Jerome,
> basically) want something different.

At least using pr_debug() doesn't match the comment, ie. the comment
says "Be verbose" but pr_debug() is silent by default.

cheers