Re: [for-4.10] Re: [PATCH v2] tools/libxl: mark special pages as reserved in e820 map for PVH

From: Julien Grall <julien.grall@linaro.org>
To: "Roger Pau Monné" <roger.pau@citrix.com>,
	"Juergen Gross" <jgross@suse.com>
Cc: xen-devel@lists.xenproject.org, julien.grall@arm.com,
	wei.liu2@citrix.com, ian.jackson@eu.citrix.com
Subject: Re: [for-4.10] Re: [PATCH v2] tools/libxl: mark special pages as reserved in e820 map for PVH
Date: Wed, 6 Dec 2017 11:50:29 +0000	[thread overview]
Message-ID: <4db6f077-9850-c9ac-0b87-f02407879ea3@linaro.org> (raw)
In-Reply-To: <20171206114746.rlbifb2djqupa7qg@MacBook-Pro-de-Roger.local>

Hi,

On 12/06/2017 11:47 AM, Roger Pau Monné wrote:
> On Wed, Dec 06, 2017 at 12:22:00PM +0100, Juergen Gross wrote:
>> On 06/12/17 10:53, Julien Grall wrote:
>>> Hi Juergen,
>>>
>>> On 12/05/2017 04:19 PM, Juergen Gross wrote:
>>>> On 05/12/17 16:23, Julien Grall wrote:
>>>>> Hi Juergen,
>>>>>
>>>>> On 04/12/17 15:49, Juergen Gross wrote:
>>>>>> On 21/11/17 12:06, Juergen Gross wrote:
>>>>>>> The "special pages" for PVH guests include the frames for console and
>>>>>>> Xenstore ring buffers. Those have to be marked as "Reserved" in the
>>>>>>> guest's E820 map, as otherwise conflicts might arise later e.g. when
>>>>>>> hotplugging memory into the guest.
>>>>>>>
>>>>>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>>>>> ---
>>>>>>> This is a bugfix for PVH guests. Please consider for 4.10.
>>>>>>
>>>>>> Ping?
>>>>>
>>>>> I was waiting an ack from tools maintainers before looking for a release
>>>>> perspective.
>>>>>
>>>>> I would recommend to tag your patch is 4.10 to help reviewers prioritize
>>>>> review on your patch. I have done it now.
>>>>>
>>>>> I am looking at releasing Xen 4.10 in the next few days. Can you explain
>>>>> the pros/cons of this patch?
>>>>
>>>> Pros: PVH guests with 4GB of memory or more will work. :-)
>>>
>>> They never worked before? Or is it a regression? If it is a regression
>>> when did it appear?
>>
>> Hmm, seems we are lucky: Linux kernel will not try to map any memory
>> there (I just tested it). So we don't need that patch in 4.10 for Linux
>> running as PVH guest. Not sure about BSD, though.
> 
> I haven't yet committed any PVHv2 support to FreeBSD, but in any case
> I always avoid using memory below 4GB just in case...

I will defer this patch post 4.10. We can add a release note if you 
think it is worth it.

Cheers,

-- 
Julien Grall

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