[PATCH] makedumpfile: Support for x86_64 1G pages

Trapp, Norbert norbert.trapp at ts.fujitsu.com
Thu Aug 30 07:19:04 EDT 2012

> -----Original Message-----
> From: Petr Tesarik [mailto:ptesarik at suse.cz]
> Sent: Tuesday, August 28, 2012 5:11 PM
> To: kexec at lists.infradead.org
> Cc: Trapp, Norbert
> Subject: [PATCH] makedumpfile: Support for x86_64 1G pages
> The PS bit is not recognized in the Page-Directory-Pointer Table (pgdir
> in Linux terms), so virtual addresses that map to a 1G page will be
> translated incorrectly.
> This bug affects both Xen and bare metal. I don't think it can be easily
> triggered in practice, because 1G mappings are created only for:
> 1. direct 1:1 mapping of physical memory, for which we don't walk the page
>    tables, but instead subtract the corresponding virtual offset, and
> 2. 1G hugepages, which are only used for userspace data.

Hello again,

With Xen not only the Linux kernel has to be considered, but the Xen
hypervisor, too.  The usage of 1 GB pages by the hypervisor is
relevant for machines with recent types of processors and more
than a small amount of memory.

With kind reagards


Norbert Trapp

Fujitsu Technology Solutions GmbH
Domagkstraße 28, D-80807 München, Germany
E-mail: Norbert.Trapp at ts.fujitsu.com
Web: ts.fujitsu.com
Company details: ts.fujitsu.com/imprint

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