linux-kernel - Re: [Xen-devel] [PATCHv2 10/10] xen/balloon: pre-allocate p2m entries for ballooned pages

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Date:	Mon, 27 Jul 2015 13:40:04 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Julien Grall <julien.grall@...rix.com>,
	David Vrabel <david.vrabel@...rix.com>,
	<xen-devel@...ts.xenproject.org>
CC:	<linux-mm@...ck.org>, Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"Daniel Kiper" <daniel.kiper@...cle.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCHv2 10/10] xen/balloon: pre-allocate p2m entries
 for ballooned pages

On 27/07/15 12:01, Julien Grall wrote:
> On 27/07/15 10:30, David Vrabel wrote:
>> On 25/07/15 00:21, Julien Grall wrote:
>>> On 24/07/2015 12:47, David Vrabel wrote:
>>>> @@ -550,6 +551,11 @@ int alloc_xenballooned_pages(int nr_pages, struct
>>>> page **pages)
>>>>           page = balloon_retrieve(true);
>>>>           if (page) {
>>>>               pages[pgno++] = page;
>>>> +#ifdef CONFIG_XEN_HAVE_PVMMU
>>>> +            ret = xen_alloc_p2m_entry(page_to_pfn(page));
>>>
>>> Don't you want to call this function only when the guest is not using
>>> auto-translated physmap?
>>
>> xen_alloc_p2m_entry() is a nop in auto-xlate guests, so no need for an
>> additional check here.
> 
> I don't have the impression it's the case or it's not obvious.

Oops. You're right.  I'll add a

	if (xen_feature(XENFEAT_auto_translated_physmap))
		return true;

Check at the top.

David

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