linux-kernel - Re: [PATCH 2/3 v9] resource: add the new I/O resource descriptor 'IORES_DESC

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Date:   Thu, 28 Mar 2019 22:00:01 +0800
From:   lijiang <lijiang@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        x86@...nel.org, hpa@...or.com, dyoung@...hat.com, bhe@...hat.com,
        Thomas.Lendacky@....com
Subject: Re: [PATCH 2/3 v9] resource: add the new I/O resource descriptor
 'IORES_DESC_RESERVED'

在 2019年03月25日 20:24, Borislav Petkov 写道:
> On Mon, Mar 25, 2019 at 02:53:02PM +0800, lijiang wrote:
>> In this function, i printed its values, and only got the value of reserved
>> type, so i changed the IORES_DESC_NONE to the IORES_DESC_RESERVED.
>>
>> In addition, after the new descriptor 'IORES_DESC_RESERVED' is introduced,
>> the IORES_DESC_NONE does not include the IORES_DESC_RESERVED any more, it
>> could miss to handle the value of the reserved type.
> 
> Yes, IORES_DESC_RESERVED is supposed to denote the e820 reserved type.
> Why should IORES_DESC_NONE include it ?!?!
> 
> IORES_DESC_NONE is, well, an invalid, i.e., "none" type:

Yes, i see. That indicates an empty area, or "void" type.

> 
> /*
>  * I/O Resource Descriptors
>  *
>  * Descriptors are used by walk_iomem_res_desc() and region_intersects()
>  * for searching a specific resource range in the iomem table.  Assign
>  * a new descriptor when a resource range supports the search interfaces.
>  * Otherwise, resource.desc must be set to IORES_DESC_NONE (0).
>  */
> 
>> Do you mean i should never touch the three chunks? If i made a mistake, i
>> will remove this changes next post.
> 
> I'm looking at the hunks below and you're changing ->desc assignments in
> some random function which doesn't look like you know what you're doing.
> Maybe it gets you what you want but it sure as hell doesn't look right
> to me.
> 
I have realized that there could be a problem with this changes. Indeed, here
it denotes an empty area instead of a reserved area.

BTW: Looks like the name of this function(__reserve_region_with_split) is a bit
misleading.

Thank you for pointing out this problem, i will correct them next post.

Lianbo