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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>, Andi Kleen <ak@muc.de>,
	linux-kernel@vger.kernel.org, virtualization@lists.osdl.org,
	xen-devel@lists.xensource.com, Chris Wright <chrisw@sous-sol.org>,
	Zachary Amsden <zach@vmware.com>,
	Ian Pratt <ian.pratt@xensource.com>,
	Christian Limpach <Christian.Limpach@cl.cam.ac.uk>,
	Jan Beulich <JBeulich@novell.com>
Subject: Re: [patch 12/21] Xen-paravirt: Allocate and free vmalloc areas
Date: Fri, 16 Feb 2007 18:48:26 +1100	[thread overview]
Message-ID: <45D561CA.3080609@yahoo.com.au> (raw)
In-Reply-To: <20070215232447.5ee67f50.akpm@linux-foundation.org>

Andrew Morton wrote:
> On Thu, 15 Feb 2007 23:08:02 -0800 Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> 
> 
>>Andrew Morton wrote:
>>
>>>This won't work when CONFIG_PREEMPT=y.  The pagefault handler will see
>>>in_atomic() and will scram.
>>>  
>>
>>Is there some other way to get the pagetable populated for the address
>>range?
>>
> 
> 
> If you really need to run atomically, that gets ugly.  Even of one were to
> run handle_mm_fault() by hand, it still needs to allocate memory.
> 
> Two ugly options might be:
> 
> a) touch all the pages, then go atomic, then touch them all again.  If
>    one of them faults (ie: you raced with swapout) then go back and try
>    again.  Obviously susceptible to livelocking.
> 
> b) Do get_user_pages() against all the pages, then go atomic, then do
>    put_page() against them all.  Of course, they can immediately get
>    swapped out.
> 
> But that function's already racy against swapout and I guess it works OK. 
> I don't have clue what it is actually trying to do, so I'm guessing madly
> here.

Well its only operating on kernel pages, and against a vmalloc region.
So it would be immune to any sort of unmapping or swapout.

Andrew's option a) should work. What's this for, and how is it not Xen
specific if nothing else in the tree needs such a weird hack?

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 

  parent reply	other threads:[~2007-02-16  7:49 UTC|newest]

Thread overview: 97+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-16  2:24 [patch 00/21] Xen-paravirt: Xen guest implementation for paravirt_ops interface Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 01/21] Xen-paravirt: Fix typo in sync_constant_test_bit()s name Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 02/21] Xen-paravirt: ignore vgacon if hardware not present Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 03/21] Xen-paravirt: Add pagetable accessors to pack and unpack pagetable entries Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 04/21] Xen-paravirt: =================================================================== Jeremy Fitzhardinge
2007-02-16  9:12   ` Andi Kleen
2007-02-16 17:32     ` Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 05/21] Xen-paravirt: paravirt_ops: hooks to set up initial pagetable Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 06/21] Xen-paravirt: paravirt_ops: allocate a fixmap slot Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 07/21] Xen-paravirt: remove ctor for pgd cache Jeremy Fitzhardinge
2007-02-16  6:04   ` Zachary Amsden
2007-02-16  8:39   ` Pekka Enberg
2007-02-16  9:19     ` Nick Piggin
2007-02-16 17:19       ` Jeremy Fitzhardinge
2007-02-16 20:33   ` Christoph Lameter
2007-02-16 23:33     ` Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 08/21] Xen-paravirt: Allow paravirt backend to choose kernel PMD sharing Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 09/21] Xen-paravirt: Allow paravirt backend to select PGD allocation alignment Jeremy Fitzhardinge
2007-02-16  2:24 ` [patch 10/21] Xen-paravirt: add hooks to intercept mm creation and destruction Jeremy Fitzhardinge
2007-02-16  6:34   ` Andrew Morton
2007-02-16  6:55     ` Jeremy Fitzhardinge
2007-02-22 20:16   ` Pavel Machek
2007-02-22 20:21     ` Jeremy Fitzhardinge
2007-02-22 20:23     ` Jeremy Fitzhardinge
2007-02-16  2:25 ` [patch 11/21] Xen-paravirt: Add apply_to_page_range() which applies a function to a pte range Jeremy Fitzhardinge
2007-02-16  6:37   ` Andrew Morton
2007-02-16  7:06     ` Jeremy Fitzhardinge
2007-02-16  7:19       ` Andrew Morton
2007-02-16  7:23         ` Jeremy Fitzhardinge
2007-02-16  7:31     ` Nick Piggin
2007-02-16  2:25 ` [patch 12/21] Xen-paravirt: Allocate and free vmalloc areas Jeremy Fitzhardinge
2007-02-16  6:43   ` Andrew Morton
2007-02-16  7:08     ` Jeremy Fitzhardinge
2007-02-16  7:24       ` Andrew Morton
2007-02-16  7:30         ` Jeremy Fitzhardinge
2007-02-16  7:49           ` Andrew Morton
2007-02-16  9:18           ` Andi Kleen
2007-02-16 11:10             ` [Xen-devel] " Keir Fraser
2007-02-16 11:34               ` Andi Kleen
2007-02-16 16:46             ` Jeremy Fitzhardinge
2007-02-16 17:10               ` [Xen-devel] " Keir Fraser
2007-02-16 17:12                 ` Keir Fraser
2007-02-16 17:27                   ` Jeremy Fitzhardinge
2007-02-16 19:06                     ` Keir Fraser
2007-02-16 19:19                       ` Keir Fraser
2007-02-16 19:26                         ` Jeremy Fitzhardinge
2007-02-16 23:29                           ` Keir Fraser
2007-02-16 23:41                             ` Jeremy Fitzhardinge
2007-02-16 17:26                 ` Hollis Blanchard
2007-02-16  7:48         ` Nick Piggin [this message]
2007-02-16  2:25 ` [patch 13/21] Xen-paravirt: Add nosegneg capability to the vsyscall page notes Jeremy Fitzhardinge
2007-02-16  6:06   ` Zachary Amsden
2007-02-16  2:25 ` [patch 14/21] Xen-paravirt: Add XEN config options and disable unsupported config options Jeremy Fitzhardinge
2007-02-16  6:14   ` Dan Hecht
2007-02-16  7:04     ` Jeremy Fitzhardinge
2007-02-16  7:52       ` Dan Hecht
2007-02-16  8:05         ` Jeremy Fitzhardinge
2007-02-16  8:37           ` Dan Hecht
2007-02-16 10:49             ` Keir Fraser
2007-02-16  7:06     ` Andrew Morton
2007-02-16  7:25       ` Jeremy Fitzhardinge
2007-02-16 10:09         ` Keir Fraser
2007-02-16 10:19           ` [Xen-devel] " Zachary Amsden
2007-02-16 10:44             ` Keir Fraser
2007-02-16 10:55               ` Zachary Amsden
2007-02-17  4:04             ` Rusty Russell
2007-02-16  6:15   ` Zachary Amsden
2007-02-16  7:33     ` Eric W. Biederman
2007-02-16  8:14       ` Ian Campbell
2007-02-16  8:24         ` Eric W. Biederman
2007-02-16  8:31           ` Zachary Amsden
2007-02-16 13:53       ` [Xen-devel] " Gerd Hoffmann
2007-02-18 11:32     ` Avi Kivity
2007-02-16  2:25 ` [patch 16/21] Xen-paravirt: Core Xen implementation Jeremy Fitzhardinge
2007-02-16  2:25 ` [patch 17/21] Xen-paravirt: Add the Xen virtual console driver Jeremy Fitzhardinge
2007-02-16  6:48   ` Andrew Morton
2007-02-16  2:25 ` [patch 18/21] Xen-paravirt: Add Xen grant table support Jeremy Fitzhardinge
2007-02-16  6:52   ` Andrew Morton
2007-02-16  6:58     ` Jeremy Fitzhardinge
2007-02-16  2:25 ` [patch 19/21] Xen-paravirt: Add the Xenbus sysfs and virtual device hotplug driver Jeremy Fitzhardinge
2007-02-16  2:25 ` [patch 20/21] Xen-paravirt: Add Xen virtual block device driver Jeremy Fitzhardinge
2007-02-16  2:25 ` [patch 21/21] Xen-paravirt: Add the Xen virtual network " Jeremy Fitzhardinge
2007-02-16  6:59 ` [patch 00/21] Xen-paravirt: Xen guest implementation for paravirt_ops interface Andrew Morton
2007-02-16  7:20   ` Jeremy Fitzhardinge
2007-02-16 20:49 ` Christoph Lameter
2007-02-16 21:04   ` Zachary Amsden
2007-02-16 21:13     ` Christoph Lameter
2007-02-16 21:48       ` Zachary Amsden
2007-02-16 21:59         ` Christoph Lameter
2007-02-16 22:10           ` Zachary Amsden
2007-02-17 13:51           ` Andi Kleen
2007-02-21 18:37             ` Christoph Lameter
2007-02-21 18:55               ` Zachary Amsden
2007-02-21 20:02               ` Jeremy Fitzhardinge
2007-02-17  5:05         ` Rusty Russell
2007-02-16 23:49   ` Jeremy Fitzhardinge
2007-02-17  4:58   ` Rusty Russell

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