Re: [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space

From: Wei Liu <wei.liu2@citrix.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	ian.jackson@eu.citrix.com, peter.huangpeng@huawei.com,
	xen-devel@lists.xen.org, Julien Grall <julien.grall@arm.com>,
	Shannon Zhao <shannon.zhao@linaro.org>,
	Shannon Zhao <zhaoshenglong@huawei.com>
Subject: Re: [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space
Date: Tue, 12 Jul 2016 17:05:59 +0100	[thread overview]
Message-ID: <20160712160559.GN23802@citrix.com> (raw)
In-Reply-To: <55c5025f-f25c-d49c-6ae0-168121ddf70f@oracle.com>

On Tue, Jul 12, 2016 at 11:21:12AM -0400, Boris Ostrovsky wrote:
> On 07/12/2016 11:13 AM, Wei Liu wrote:
> > On Tue, Jul 12, 2016 at 11:08:47AM -0400, Boris Ostrovsky wrote:
> >> On 07/12/2016 10:57 AM, Shannon Zhao wrote:
> >>> On 2016年07月12日 22:50, Wei Liu wrote:
> >>>> On Tue, Jul 12, 2016 at 10:42:07PM +0800, Shannon Zhao wrote:
> >>>>>>>>>>>>>>>>>>>>>>>> Does it mean we would need to update the slack to take into account the ACPI
> >>>>>>>>>>>>>>>>>>>>>>>> blob?
> >>>>>>>>>>>>>>>> Yes, we need to take into account the ACPI blob. Probably not in the
> >>>>>>>>>>>>>>>> slack but directly in mam_memkb.
> >>>>>>>>>>>> Sorry, I'm not sure understand this. I found the b_info->max_memkb but
> >>>>>>>>>>>> didn't find the slack you said. And how to fix this? Update
> >>>>>>>>>>>> b_info->max_memkb or the slack?
> >>>>>>>> Can you calculate the size of your payload and add that to max_memkb?
> >>>>>>>>
> >>>>>> Yeah, but the size will be changed if we change the tables in the future
> >>>>>> and this also should consider x86, right?
> >>>> That could easily be solved by introducing a function to calculate the
> >>>> size, right?
> >>> Oh, I'm not familiar with this. Let's clarify on this. It can add the
> >>> size to max_memkb after generating the ACPI tables and before loading
> >>> the tables to guest space and it doesn't have to add the size at
> >>> libxl__domain_build_info_setdefault(), right?
> > Hmm... I would like to think a bit more about this. But before dwelling
> > on this too much...
> >
> >> This was discussed before: ACPI tables are part of RAM whose size is
> >> specified by the config file (and is reflected in max_memkb I believe).
> >> It may not be presented to the guest as RAM (i.e. on x86 it is labeled
> >> by BIOS (or whoever) as a dedicated type in e820) but it still resides
> >> in DIMMs.
> >>
> >> I believe we should not increase memory resources for ACPI tables.
> >>
> > This is an interesting point. If there is already such resolution I will
> > be happy to follow it.
> >
> > Any reference?
> 
> The last one (that I can find) is
>    
> https://lists.xenproject.org/archives/html/xen-devel/2016-07/msg00821.html
> 
> (conveniently in the same thread is the one we have been using to talk
> about licensing)
> 

Ah, OK.

Shannon, you don't need to modify max_memkb then. 

Wei.

> -boris
> 
> 

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