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[Xen-devel] Re: [PATCH] calling zap_low_mappings breaks xen boot on the

To: "Subrahmanian, Raj" <raj.subrahmanian@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] calling zap_low_mappings breaks xen boot on the es7000
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 24 May 2007 10:04:53 +0100
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Thread-topic: [PATCH] calling zap_low_mappings breaks xen boot on the es7000
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On 23/5/07 22:16, "Subrahmanian, Raj" <raj.subrahmanian@xxxxxxxxxx> wrote:

>> Either we should just delay the zap_low_mappings() call, or
>> fix your code to map_domain_page()/unmap_domain_page(). How
>> late in boot do you need the low mappings?
> This patch delays the zap_low_mappings() call until after the
> smp_prepare_cpus call. With this patch, I am able to run Xen on the
> ES7000 and a Dell SC 1430.

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.

 -- Keir

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