Re: [PATCH 1/2] xen: arm64: doc: Add the requirement that SCR_EL3.HCE is enabled

[Dirk Behme <dirk.behme@de.bosch.com>]

On 20.04.2016 15:21, Julien Grall wrote:
> (CC REST maintainers)
>
> Hello Dirk,
>
> Please CC the relevant maintainers for this patch. You can use
> scripts/get_maintainers.pl for this purpose.
>
> On 19/04/16 06:59, Dirk Behme wrote:
>> On ARM64 Linux the HVC instruction is used to trap into Xen. As this
>> can be set only at EL3, i.e. outside from Xen, document this boot
>> requirement.
>>
>> Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
>> ---
>>   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 9802e5e..ffc9029 100644
>> --- a/docs/misc/arm/booting.txt
>> +++ b/docs/misc/arm/booting.txt
>> @@ -23,6 +23,10 @@ The exceptions to this on 32-bit ARM are as follows:
>>
>>   There are no exception on 64-bit ARM.
>>
>> +On ARM64 Linux it has to be ensured that the Secure Configuration
>> +Register has the HVC instructions enabled at EL1 and above
>> +(SCR_EL3.HCE == 1).
>
> The requirement is the same for ARM32 (SCR.HCE == 1).
>
> I would create a specific section in this documentation to list what the
> firmware should do in EL3 before starting Xen.


Done:

http://lists.xen.org/archives/html/xen-devel/2016-04/msg02687.html


> In addition to this patch, I would add a check in Xen to make sure the
> Hyp calls have been enabled by the firmware.


Hmm, I have to re-read the documentation how to do this in EL2. We can't 
read SCR_EL3 in EL2?


Best regards

Dirk


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