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

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Date:	Fri, 27 Mar 2015 14:28:14 +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: Thursday, March 26, 2015 2:40 AM
> To: KY Srinivasan
> Cc: Haiyang Zhang; devel@...uxdriverproject.org; linux-
> kernel@...r.kernel.org; Dexuan Cui
> 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.

Yes; looks good.

K. Y
> 
> >
> > 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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