linux-kernel - Re: [PATCH 1/2] x86: Add Isolated Memory Regions for Quark X1000

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Message-ID: <54AE73C7.90009@nexus-software.ie>
Date:	Thu, 08 Jan 2015 12:10:47 +0000
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	"Ong, Boon Leong" <boon.leong.ong@...el.com>,
	Darren Hart <dvhart@...radead.org>
CC:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86: Add Isolated Memory Regions for Quark X1000

On 07/01/15 23:45, Ong, Boon Leong wrote:
>> Since BIOS and grub code both use 0x00000000 as the 'off' address I think it
>> makes sense for the kernel to continue to use that address.
>
> Just add on top of what Daren mentioned in another mail, based on the Quark document,
> the base address can start from zero. Say lo=0, hi=0, and WM & RM may be changed from default value,
> 1st 1KiB will be marked as IMR. It seems to me that there is no good way to test if an IMR is 'occupied' and/or 'enabled'
> since enable-bit is not available. But, what is benefit of testing against lo=0 & hi=0? The logic to calculate size will work under
> lo=0 & hi=0 anway.

Hi Boon Leong.

I think it does make sense to add a check for rmask and wmask in the 
'access all' state when determining if an IMR is enabled on X1000 or not.

>> My own view is that it's not really desirable and easier to debug IMRs
>> generally on a platform if overlaps aren't allowed.
> I do agree on the benefit listed above. Perhaps, you can add explanation here
> to mention the design decision.

Will do.


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