From: Julien Grall <jgrall@amazon.com>

In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
we decided to require Xen to be loaded below 5 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

Signed-off-by: Julien Grall <jgrall@amazon.com>

----

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, 4 insertions(+)

diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
index 02f7bb65ec6d..c6bdeafe5e5b 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -21,6 +21,10 @@ 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.
 
+The exceptions to this on 64-bit ARM are as follows:
+
+ Xen binary should be loaded in memory below 2 TiB.
+
 There are no exception on 64-bit ARM.
 
 Booting Guests
-- 
2.40.1

Hi Julien,

On 24/10/2023 12:09, Julien Grall 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 5 TiB to simplify
s/5/2

> 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
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ----
one less '-'

> 
> 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, 4 insertions(+)
> 
> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
> index 02f7bb65ec6d..c6bdeafe5e5b 100644
> --- a/docs/misc/arm/booting.txt
> +++ b/docs/misc/arm/booting.txt
> @@ -21,6 +21,10 @@ 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.
> 
> +The exceptions to this on 64-bit ARM are as follows:
> +
> + Xen binary should be loaded in memory below 2 TiB.
> +
>  There are no exception on 64-bit ARM.
This sentence needs to be dropped then.

With that:
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

~Michal

On 24/10/2023 11:23, Michal Orzel wrote:
> Hi Julien,

Hi,

> On 24/10/2023 12:09, Julien Grall 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 5 TiB to simplify
> s/5/2

Ah yes. I keep having 2 TiB.

>> 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
>>
>> Signed-off-by: Julien Grall <jgrall@amazon.com>
>>
>> ----
> one less '-'

Yes. I forgot to call 'sed -i 's/^----/---/' *.patch' before sending (I 
use ---- to prevent my pacthqueue management tool to strip anything 
after ---).

> 
>>
>> 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, 4 insertions(+)
>>
>> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
>> index 02f7bb65ec6d..c6bdeafe5e5b 100644
>> --- a/docs/misc/arm/booting.txt
>> +++ b/docs/misc/arm/booting.txt
>> @@ -21,6 +21,10 @@ 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.
>>
>> +The exceptions to this on 64-bit ARM are as follows:
>> +
>> + Xen binary should be loaded in memory below 2 TiB.
>> +
>>   There are no exception on 64-bit ARM.
> This sentence needs to be dropped then.

Whoops yes.

> 
> With that:
> Reviewed-by: Michal Orzel <michal.orzel@amd.com>

Thanks!

Cheers,

-- 
Julien Grall

On 24/10/2023 11:09, Julien Grall 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 5 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

I forgot to add a link to

[1] 20231013122658.1270506-3-leo.yan@linaro.org

Cheers,

-- 
Julien Grall