diff mbox series

[for-4.19,v2] docs/arm: Document where Xen should be loaded in memory

Message ID 20231024102858.29067-1-julien@xen.org (mailing list archive)
State New, archived
Headers show
Series [for-4.19,v2] docs/arm: Document where Xen should be loaded in memory | expand

Commit Message

Julien Grall Oct. 24, 2023, 10:28 a.m. UTC 
From: Julien Grall <jgrall@amazon.com>

In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
we decided to require Xen to be loaded below 2 TiB to simplify
the logic to enable the MMU. The limit was decided based on
how known platform boot plus some slack.

We had a recent report that this is not sufficient on the AVA
platform with a old firmware [1]. But the restriction is not
going to change in Xen 4.18. So document the limit clearly
in docs/misc/arm/booting.txt.

[1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

---

    Changes in v2:
        - The limit is 2 TiB no 5
        - Remove unnecessary sentence in the docs
        - Add missing link
        - Add Michal's reviewed-by

I couldn't find a nice way to document it in SUPPORT.md. So I decided
to only document the restrict in docs/misc/arm/booting.txt for now.

I also couldn't find any way from GRUB/UEFI (I didn't look much) to
specify the loading address.
---
 docs/misc/arm/booting.txt | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Bertrand Marquis Oct. 24, 2023, 1:30 p.m. UTC | #1 
Hi Julien,

> On 24 Oct 2023, at 12:28, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
> we decided to require Xen to be loaded below 2 TiB to simplify
> the logic to enable the MMU. The limit was decided based on
> how known platform boot plus some slack.
> 
> We had a recent report that this is not sufficient on the AVA
> platform with a old firmware [1]. But the restriction is not
> going to change in Xen 4.18. So document the limit clearly
> in docs/misc/arm/booting.txt.
> 
> [1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> Reviewed-by: Michal Orzel <michal.orzel@amd.com>

Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand

> 
> ---
> 
>    Changes in v2:
>        - The limit is 2 TiB no 5
>        - Remove unnecessary sentence in the docs
>        - Add missing link
>        - Add Michal's reviewed-by
> 
> I couldn't find a nice way to document it in SUPPORT.md. So I decided
> to only document the restrict in docs/misc/arm/booting.txt for now.
> 
> I also couldn't find any way from GRUB/UEFI (I didn't look much) to
> specify the loading address.
> ---
> docs/misc/arm/booting.txt | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
> index 02f7bb65ec6d..547f58a7d981 100644
> --- a/docs/misc/arm/booting.txt
> +++ b/docs/misc/arm/booting.txt
> @@ -21,7 +21,9 @@ The exceptions to this on 32-bit ARM are as follows:
>  zImage protocol should still be used and not the stricter "raw
>  (non-zImage)" protocol described in arm/Booting.
> 
> -There are no exception on 64-bit ARM.
> +The exceptions to this on 64-bit ARM are as follows:
> +
> + Xen binary should be loaded in memory below 2 TiB.
> 
> Booting Guests
> --------------
> -- 
> 2.40.1
>
Stefano Stabellini Oct. 24, 2023, 7:52 p.m. UTC | #2 
On Tue, 24 Oct 2023, Bertrand Marquis wrote:
> Hi Julien,
> 
> > On 24 Oct 2023, at 12:28, Julien Grall <julien@xen.org> wrote:
> > 
> > From: Julien Grall <jgrall@amazon.com>
> > 
> > In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
> > we decided to require Xen to be loaded below 2 TiB to simplify
> > the logic to enable the MMU. The limit was decided based on
> > how known platform boot plus some slack.
> > 
> > We had a recent report that this is not sufficient on the AVA
> > platform with a old firmware [1]. But the restriction is not
> > going to change in Xen 4.18. So document the limit clearly
> > in docs/misc/arm/booting.txt.
> > 
> > [1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org
> > 
> > Signed-off-by: Julien Grall <jgrall@amazon.com>
> > Reviewed-by: Michal Orzel <michal.orzel@amd.com>
> 
> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Added for for-4.19
Henry Wang Oct. 25, 2023, 7:47 a.m. UTC | #3 
Hi Julien,

> On Oct 24, 2023, at 18:28, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
> we decided to require Xen to be loaded below 2 TiB to simplify
> the logic to enable the MMU. The limit was decided based on
> how known platform boot plus some slack.
> 
> We had a recent report that this is not sufficient on the AVA
> platform with a old firmware [1]. But the restriction is not
> going to change in Xen 4.18. So document the limit clearly
> in docs/misc/arm/booting.txt.
> 
> [1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> Reviewed-by: Michal Orzel <michal.orzel@amd.com>

Release-acked-by: Henry Wang <Henry.Wang@arm.com>

Kind regards,
Henry
Julien Grall Oct. 25, 2023, 10:03 a.m. UTC | #4 
Hi Stefano,

On 24/10/2023 20:52, Stefano Stabellini wrote:
> On Tue, 24 Oct 2023, Bertrand Marquis wrote:
>> Hi Julien,
>>
>>> On 24 Oct 2023, at 12:28, Julien Grall <julien@xen.org> wrote:
>>>
>>> From: Julien Grall <jgrall@amazon.com>
>>>
>>> In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
>>> we decided to require Xen to be loaded below 2 TiB to simplify
>>> the logic to enable the MMU. The limit was decided based on
>>> how known platform boot plus some slack.
>>>
>>> We had a recent report that this is not sufficient on the AVA
>>> platform with a old firmware [1]. But the restriction is not
>>> going to change in Xen 4.18. So document the limit clearly
>>> in docs/misc/arm/booting.txt.
>>>
>>> [1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org
>>>
>>> Signed-off-by: Julien Grall <jgrall@amazon.com>
>>> Reviewed-by: Michal Orzel <michal.orzel@amd.com>
>>
>> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
> 
> Added for for-4.19

It was actually meant for 4.18 as we didn't want to include the patch to 
increase the reserved area for the identity mapping [1]. But I failed to 
use the proper tag.

Henry provided a release-ack and the patch is now committed.

Cheers,

[1]  https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org
Stefano Stabellini Oct. 25, 2023, 9:01 p.m. UTC | #5 
On Wed, 25 Oct 2023, Julien Grall wrote:
> Hi Stefano,
> 
> On 24/10/2023 20:52, Stefano Stabellini wrote:
> > On Tue, 24 Oct 2023, Bertrand Marquis wrote:
> > > Hi Julien,
> > > 
> > > > On 24 Oct 2023, at 12:28, Julien Grall <julien@xen.org> wrote:
> > > > 
> > > > From: Julien Grall <jgrall@amazon.com>
> > > > 
> > > > In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
> > > > we decided to require Xen to be loaded below 2 TiB to simplify
> > > > the logic to enable the MMU. The limit was decided based on
> > > > how known platform boot plus some slack.
> > > > 
> > > > We had a recent report that this is not sufficient on the AVA
> > > > platform with a old firmware [1]. But the restriction is not
> > > > going to change in Xen 4.18. So document the limit clearly
> > > > in docs/misc/arm/booting.txt.
> > > > 
> > > > [1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@linaro.org
> > > > 
> > > > Signed-off-by: Julien Grall <jgrall@amazon.com>
> > > > Reviewed-by: Michal Orzel <michal.orzel@amd.com>
> > > 
> > > Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
> > 
> > Added for for-4.19
> 
> It was actually meant for 4.18 as we didn't want to include the patch to
> increase the reserved area for the identity mapping [1]. But I failed to use
> the proper tag.
> 
> Henry provided a release-ack and the patch is now committed.

Thanks for letting me know. I took the commit out of for-4.19 and
rebased it.
diff mbox series

Patch

diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
index 02f7bb65ec6d..547f58a7d981 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -21,7 +21,9 @@  The exceptions to this on 32-bit ARM are as follows:
  zImage protocol should still be used and not the stricter "raw
  (non-zImage)" protocol described in arm/Booting.
 
-There are no exception on 64-bit ARM.
+The exceptions to this on 64-bit ARM are as follows:
+
+ Xen binary should be loaded in memory below 2 TiB.
 
 Booting Guests
 --------------