Re: [PATCH V3 0/8] xen: Switch to virtual mapped linear p2m list

From: Juergen Gross
Date: Thu Nov 20 2014 - 00:09:24 EST

On 11/19/2014 09:41 PM, Konrad Rzeszutek Wilk wrote:
On Tue, Nov 11, 2014 at 06:43:38AM +0100, Juergen Gross wrote:
Paravirtualized kernels running on Xen use a three level tree for
translation of guest specific physical addresses to machine global
addresses. This p2m tree is used for construction of page table
entries, so the p2m tree walk is performance critical.

By using a linear virtual mapped p2m list accesses to p2m elements
can be sped up while even simplifying code. To achieve this goal
some p2m related initializations have to be performed later in the
boot process, as the final p2m list can be set up only after basic
memory management functions are available.

Hey Juergen,

I finially finished looking at the patchset. Had some comments,
some questions that I hope can make it in the patch so that in
six months or so when somebody looks at the code they can
understand the subtle pieces.


OTOH: What was hard to write should be hard to read ;-)

Looking forward to the v4! (Thought keep in mind that next week
is Thanksgiving week so won't be able to look much after Wednesday)

Let's see how testing is going. Setting up the test system wasn't
very smooth due to some unrelated issues.

arch/x86/include/asm/pgtable_types.h | 1 +
arch/x86/include/asm/xen/page.h | 49 +-
arch/x86/mm/pageattr.c | 20 +
arch/x86/xen/mmu.c | 38 +-
arch/x86/xen/p2m.c | 1315 ++++++++++++++--------------------
arch/x86/xen/setup.c | 460 ++++++------
arch/x86/xen/xen-ops.h | 6 +-
7 files changed, 854 insertions(+), 1035 deletions(-)

And best of - we are deleting more code!

Indeed. But it's a shame the beautiful ASCII-art in p2m.c is part of the

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