* Criteria for dom0_gnttab_start
@ 2014-10-21 11:54 Vijay Kilari
2014-10-21 12:04 ` Ian Campbell
0 siblings, 1 reply; 6+ messages in thread
From: Vijay Kilari @ 2014-10-21 11:54 UTC (permalink / raw)
To: Ian Campbell, Stefano Stabellini
Cc: Prasun Kapoor, Julien Grall, manishjaggi.oss,
xen-devel@lists.xen.org
Hi,
What is the criteria for setting dom0_gnttab_start and size for a
platform. Till now I am using default gnttab map
Grant table range: 0x000000b0000000-0x000000b0020000
Regards
Vijay
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Criteria for dom0_gnttab_start
2014-10-21 11:54 Criteria for dom0_gnttab_start Vijay Kilari
@ 2014-10-21 12:04 ` Ian Campbell
2014-10-21 12:12 ` Julien Grall
0 siblings, 1 reply; 6+ messages in thread
From: Ian Campbell @ 2014-10-21 12:04 UTC (permalink / raw)
To: Vijay Kilari
Cc: Prasun Kapoor, Julien Grall, xen-devel@lists.xen.org,
manishjaggi.oss, Stefano Stabellini
On Tue, 2014-10-21 at 17:24 +0530, Vijay Kilari wrote:
> Hi,
>
> What is the criteria for setting dom0_gnttab_start and size for a
> platform.
It simply needs to be an area of the IPA address space which is not
populated by anything else. Since dom0's MMIO space is mapped 1:1 with
the host PA address space it seems easiest/safest to find a hole in the
real physical space and use that.
If there is no such hole available then using the space occupied by some
device which is not passed to dom0 (e.g. is blacklisted, or used by Xen)
will suffice.
For an arm32 platform it should be below 4G.
Sizewise anything from 0x20000 should do.
Alignmentwise I suppose 2M aligned would be preferable for the guest,
but it's not mandatory.
Ian.
> Till now I am using default gnttab map
>
> Grant table range: 0x000000b0000000-0x000000b0020000
>
> Regards
> Vijay
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Criteria for dom0_gnttab_start
2014-10-21 12:04 ` Ian Campbell
@ 2014-10-21 12:12 ` Julien Grall
2014-10-21 12:14 ` Ian Campbell
0 siblings, 1 reply; 6+ messages in thread
From: Julien Grall @ 2014-10-21 12:12 UTC (permalink / raw)
To: Ian Campbell, Vijay Kilari
Cc: Prasun Kapoor, xen-devel@lists.xen.org, manishjaggi.oss,
Stefano Stabellini
On 10/21/2014 01:04 PM, Ian Campbell wrote:
> On Tue, 2014-10-21 at 17:24 +0530, Vijay Kilari wrote:
>> What is the criteria for setting dom0_gnttab_start and size for a
>> platform.
>
> It simply needs to be an area of the IPA address space which is not
> populated by anything else. Since dom0's MMIO space is mapped 1:1 with
> the host PA address space it seems easiest/safest to find a hole in the
> real physical space and use that.
>
> If there is no such hole available then using the space occupied by some
> device which is not passed to dom0 (e.g. is blacklisted, or used by Xen)
> will suffice.
>
> For an arm32 platform it should be below 4G.
Even on aarch64 platform, it will be better to have this range below 4G.
I'm thinking about having a 32 bit DOM0 on top on a 64 bit Xen. Though,
this may not happen often but we are currently supported this
possibility for DOM0.
Regards,
--
Julien Grall
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Criteria for dom0_gnttab_start
2014-10-21 12:12 ` Julien Grall
@ 2014-10-21 12:14 ` Ian Campbell
2014-10-21 12:44 ` Vijay Kilari
0 siblings, 1 reply; 6+ messages in thread
From: Ian Campbell @ 2014-10-21 12:14 UTC (permalink / raw)
To: Julien Grall; +Cc: xen-devel@lists.xen.org, Vijay Kilari, Stefano Stabellini
On Tue, 2014-10-21 at 13:12 +0100, Julien Grall wrote:
> On 10/21/2014 01:04 PM, Ian Campbell wrote:
> > On Tue, 2014-10-21 at 17:24 +0530, Vijay Kilari wrote:
> >> What is the criteria for setting dom0_gnttab_start and size for a
> >> platform.
> >
> > It simply needs to be an area of the IPA address space which is not
> > populated by anything else. Since dom0's MMIO space is mapped 1:1 with
> > the host PA address space it seems easiest/safest to find a hole in the
> > real physical space and use that.
> >
> > If there is no such hole available then using the space occupied by some
> > device which is not passed to dom0 (e.g. is blacklisted, or used by Xen)
> > will suffice.
> >
> > For an arm32 platform it should be below 4G.
>
> Even on aarch64 platform, it will be better to have this range below 4G.
>
> I'm thinking about having a 32 bit DOM0 on top on a 64 bit Xen. Though,
> this may not happen often but we are currently supported this
> possibility for DOM0.
True.
Ian.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Criteria for dom0_gnttab_start
2014-10-21 12:14 ` Ian Campbell
@ 2014-10-21 12:44 ` Vijay Kilari
2014-10-21 12:59 ` Ian Campbell
0 siblings, 1 reply; 6+ messages in thread
From: Vijay Kilari @ 2014-10-21 12:44 UTC (permalink / raw)
To: Ian Campbell; +Cc: Julien Grall, xen-devel@lists.xen.org, Stefano Stabellini
On Tue, Oct 21, 2014 at 5:44 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:
> On Tue, 2014-10-21 at 13:12 +0100, Julien Grall wrote:
>> On 10/21/2014 01:04 PM, Ian Campbell wrote:
>> > On Tue, 2014-10-21 at 17:24 +0530, Vijay Kilari wrote:
>> >> What is the criteria for setting dom0_gnttab_start and size for a
>> >> platform.
>> >
>> > It simply needs to be an area of the IPA address space which is not
>> > populated by anything else. Since dom0's MMIO space is mapped 1:1 with
>> > the host PA address space it seems easiest/safest to find a hole in the
>> > real physical space and use that.
>> >
>> > If there is no such hole available then using the space occupied by some
>> > device which is not passed to dom0 (e.g. is blacklisted, or used by Xen)
>> > will suffice.
Thanks for the inputs.
Assume arm64 platform has 4GB physical RAM starting from 0x0
and all MMIO regions are beyond 4GB. For Xen the physical RAM start
address is specified at 12MB - 4GB
by UEFI.The first 12MB PA is used by Secure world.
In such case, can we specify dom0_gnttab_start anywhere within 0 to
12MB IPA address?
OR can I reserve some physical address space within 4GB and use it?
>> >
>> > For an arm32 platform it should be below 4G.
>>
>> Even on aarch64 platform, it will be better to have this range below 4G.
>>
>> I'm thinking about having a 32 bit DOM0 on top on a 64 bit Xen. Though,
>> this may not happen often but we are currently supported this
>> possibility for DOM0.
>
> True.
>
> Ian.
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Criteria for dom0_gnttab_start
2014-10-21 12:44 ` Vijay Kilari
@ 2014-10-21 12:59 ` Ian Campbell
0 siblings, 0 replies; 6+ messages in thread
From: Ian Campbell @ 2014-10-21 12:59 UTC (permalink / raw)
To: Vijay Kilari; +Cc: Julien Grall, xen-devel@lists.xen.org, Stefano Stabellini
On Tue, 2014-10-21 at 18:14 +0530, Vijay Kilari wrote:
> On Tue, Oct 21, 2014 at 5:44 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:
> > On Tue, 2014-10-21 at 13:12 +0100, Julien Grall wrote:
> >> On 10/21/2014 01:04 PM, Ian Campbell wrote:
> >> > On Tue, 2014-10-21 at 17:24 +0530, Vijay Kilari wrote:
> >> >> What is the criteria for setting dom0_gnttab_start and size for a
> >> >> platform.
> >> >
> >> > It simply needs to be an area of the IPA address space which is not
> >> > populated by anything else. Since dom0's MMIO space is mapped 1:1 with
> >> > the host PA address space it seems easiest/safest to find a hole in the
> >> > real physical space and use that.
> >> >
> >> > If there is no such hole available then using the space occupied by some
> >> > device which is not passed to dom0 (e.g. is blacklisted, or used by Xen)
> >> > will suffice.
>
> Thanks for the inputs.
>
> Assume arm64 platform has 4GB physical RAM starting from 0x0
> and all MMIO regions are beyond 4GB. For Xen the physical RAM start
> address is specified at 12MB - 4GB
> by UEFI.The first 12MB PA is used by Secure world.
> In such case, can we specify dom0_gnttab_start anywhere within 0 to
> 12MB IPA address?
I think so, yes, since NS world will never be able to use that 12MB. I
assume that the EFI address map (or DTB) marks that region as reserved?
> OR can I reserve some physical address space within 4GB and use it?
You'd have to tell Xen not to use it as normal RAM for dom0, which would
probably involve some hacks in the domain builder, best avoided I think.
Ian.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-10-21 12:59 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-10-21 11:54 Criteria for dom0_gnttab_start Vijay Kilari
2014-10-21 12:04 ` Ian Campbell
2014-10-21 12:12 ` Julien Grall
2014-10-21 12:14 ` Ian Campbell
2014-10-21 12:44 ` Vijay Kilari
2014-10-21 12:59 ` Ian Campbell
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.