linux-kernel - Re: [PATCH 0/1] Drivers: hv: hv_balloon: do not online pages in offline blocks

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Message-ID: <877fu4rtax.fsf@vitty.brq.redhat.com>
Date:	Thu, 26 Mar 2015 10:39:50 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	KY Srinivasan <kys@...rosoft.com>
Cc:	Haiyang Zhang <haiyangz@...rosoft.com>,
	"devel\@linuxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Dexuan Cui <decui@...rosoft.com>
Subject: Re: [PATCH 0/1] Drivers: hv: hv_balloon: do not online pages in offline blocks

KY Srinivasan <kys@...rosoft.com> writes:

>> -----Original Message-----
>> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
>> Sent: Wednesday, March 25, 2015 11:02 AM
>> To: KY Srinivasan
>> Cc: Haiyang Zhang; devel@...uxdriverproject.org; linux-
>> kernel@...r.kernel.org; Dexuan Cui
>> Subject: [PATCH 0/1] Drivers: hv: hv_balloon: do not online pages in offline
>> blocks
>> 
>> Patch 1/1 is rather a hackaround. The root cause of the issue is the fact that
>> we're adding not fully backed memory blocks and allow to online them. It is
>> relatively easy to forbid that and add only fully backed 128Mb regions. The
>> whole
>> driver code will be much simpler: hv_bring_pgs_online() and
>> hv_online_page()
>> will go away, ha_region_mutex won't probably be required,... Please let me
>> know
>> if you think I should follow this way.
>
> Vitaly,
>
> The main issue I had to address here was that Windows has a 2M alignment for memory
> hot add while Linux has a 128M alignment requirement. Furthermore, we will also have to deal with
> the case where only a partial 128MB block might be hot-added. The strategy I chose of selectively 
> onlining pages in a properly aligned block that would be hot added was
> to address the above two issues.

Yes, we can keep things this was, basically everyhting works. I just
wanted to highlight the other possible solution for the issue which is
also a major simplification for the driver.

So what do you think about my patch? We definitely should avoid onlining
pages in offline blocks.

>
> Regards,
>
> K. Y
>> 
>> Vitaly Kuznetsov (1):
>>   Drivers: hv: hv_balloon: do not online pages in offline blocks
>> 
>>  drivers/hv/hv_balloon.c | 12 +++++++++++-
>>  1 file changed, 11 insertions(+), 1 deletion(-)
>> 
>> --
>> 1.9.3

-- 
  Vitaly
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