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

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Message-ID: <BY2PR0301MB07117A35A981B98CAE313D14A00B0@BY2PR0301MB0711.namprd03.prod.outlook.com>
Date:	Wed, 25 Mar 2015 18:31:03 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	Haiyang Zhang <haiyangz@...rosoft.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel@...r.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



> -----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.

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

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