linux-kernel - Re: [PATCH 06/19] x86, mm: setup page table in top-down

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Message-ID: <CAE9FiQXARsxX61htTrF5Z7EGRi2dANrUUOa4BqaQBVwbyaKcNw@mail.gmail.com>
Date:	Tue, 23 Oct 2012 11:47:48 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/19] x86, mm: setup page table in top-down

On Tue, Oct 23, 2012 at 5:16 AM, Stefano Stabellini
<stefano.stabellini@...citrix.com> wrote:
> On Mon, 22 Oct 2012, Yinghai Lu wrote:
>> On Mon, Oct 22, 2012 at 11:17 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>> > On Mon, Oct 22, 2012 at 6:19 AM, Stefano Stabellini
>>
>> > How about put sth:
>> > ---
>> > Xen mmu requires pages from this function should be directly mapped already.
>> > ---
>> >
>> > or you can introduce some doc tag specially that we can out those
>> > assumption easily?
>>
>> I add
>>
>> /* Xen requires pages from this function should be directly mapped already */
>>
>> in   [PATCH] x86, mm: Add alloc_low_pages(num)
>>
>> hope you are happy with that.
>>
>
> It is not bad, but let's just fix the English a bit and give more
> context:
>
> /* Pages returned by this function are already directly mapped.
>  *
>  * Changing that is likely to break Xen, see commit
>  * 279b706bf800b5967037f492dbe4fc5081ad5d0f for more information on the
>  * subject.
>  */


I put your change in separate patch.

http://git.kernel.org/?p=linux/kernel/git/yinghai/linux-yinghai.git;a=patch;h=bc6e8a77f049f3ecaad291329238367af044aa57

>From bc6e8a77f049f3ecaad291329238367af044aa57 Mon Sep 17 00:00:00 2001
From: Stefano Stabellini <stefano.stabellini@...citrix.com>
Date: Tue, 23 Oct 2012 11:24:07 -0700
Subject: [PATCH] x86, mm: Add pointer about Xen mmu requirement for
 alloc_low_pages

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
---
 arch/x86/mm/init.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index e98a4b8..88f90f7 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -25,6 +25,13 @@ unsigned long __meminitdata pgt_buf_top;

 static unsigned long min_pfn_mapped;

+/*
+ * Pages returned are already directly mapped.
+ *
+ * Changing that is likely to break Xen, see commit
+ * 279b706bf800b5967037f492dbe4fc5081ad5d0f for more information on the
+ * subject.
+ */
 __ref void *alloc_low_pages(unsigned int num)
 {
 	unsigned long pfn;
-- 
1.7.7.6
--
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