From: Keir Fraser <keir@xensource.com>
Subject: Re: RE: [PATCH] calling zap_low_mappings breaks xen
	boot on the es7000
Date: Fri, 25 May 2007 13:39:51 +0100
Message-ID: <C27C97A7.F848%keir@xensource.com>
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To: "Subrahmanian, Raj" <raj.subrahmanian@unisys.com>, xen-devel@lists.xensource.com

On 25/5/07 13:24, "Subrahmanian, Raj" <raj.subrahmanian@unisys.com> wrote:

>> So where is the late low-memory access happening? There's not
>> that much es7000-specific code. It can't be hard to fix
>> properly. If the physical pointer is known to be below 1MB you
>> can just __va() it. If not you may need to use a fixmap, or
>> acpi_map_table, or just __va() only on x86_64. I'd like to
>> keep the zap as early as possible to catch truly erroneous low
>> pointers.
> I will look into that code and fix it.
> If you don't mind me asking, what exactly does zap_low_mappings do? I am
> not able to figure it out looking at the code.

It removes the 1:1 mapping of physical memory at virtual address 0x0.

 -- Keir