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

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

[Dirk Behme]

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).
+
 [1] linux/Documentation/arm/Booting
 Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
 
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[PATCH 2/2] xen: arm64: doc: Add some details about interrupt handling

[Dirk Behme]

In some mailing list discussion

http://lists.xen.org/archives/html/xen-devel/2016-04/msg00214.html

some details about the interrupt handling of Xen were given.
Add that so it's not forgotten.

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
---
Note: I'd be happy to move this to an other documentation file if
      any other file fits better.

 docs/misc/arm/booting.txt | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
index ffc9029..69b7d81 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -27,6 +27,21 @@ 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).
 
+
+Interrupt usage
+===============
+
+All interrupts are taken by Xen. The function do_IRQ in Xen will
+dispatch the IRQ either to a guest or call a Xen specific handler.
+
+Xen handles only a limited number of interrupt:
+* timers
+* UART
+* SMMU
+
+The rest is either routed to guests or blacklisted by Xen.
+
+
 [1] linux/Documentation/arm/Booting
 Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
 
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Re: [PATCH 2/2] xen: arm64: doc: Add some details about interrupt handling

[Julien Grall]

Hello Dirk,

On 19/04/16 06:59, Dirk Behme wrote:
> In some mailing list discussion
>
> http://lists.xen.org/archives/html/xen-devel/2016-04/msg00214.html
>
> some details about the interrupt handling of Xen were given.
> Add that so it's not forgotten.

For your information, this is described on the wiki [1]. Although, not 
in the most obvious place.

I would prefer to see this kind of documentation on the wiki page under 
"Porting Xen on a new SOC".

>
> Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
> ---
> Note: I'd be happy to move this to an other documentation file if
>        any other file fits better.
>
>   docs/misc/arm/booting.txt | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
>
> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
> index ffc9029..69b7d81 100644
> --- a/docs/misc/arm/booting.txt
> +++ b/docs/misc/arm/booting.txt
> @@ -27,6 +27,21 @@ 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).
>
> +
> +Interrupt usage
> +===============
> +
> +All interrupts are taken by Xen. The function do_IRQ in Xen will
> +dispatch the IRQ either to a guest or call a Xen specific handler.
> +
> +Xen handles only a limited number of interrupt:
> +* timers
> +* UART
> +* SMMU
> +
> +The rest is either routed to guests or blacklisted by Xen.
> +
> +
>   [1] linux/Documentation/arm/Booting
>   Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
>
>

Regards,

[1] 
http://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions_whitepaper

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Re: [PATCH 2/2] xen: arm64: doc: Add some details about interrupt handling

[Dirk Behme]

Hi Julien,

On 20.04.2016 15:26, Julien Grall wrote:
> Hello Dirk,
>
> On 19/04/16 06:59, Dirk Behme wrote:
>> In some mailing list discussion
>>
>> http://lists.xen.org/archives/html/xen-devel/2016-04/msg00214.html
>>
>> some details about the interrupt handling of Xen were given.
>> Add that so it's not forgotten.
>
> For your information, this is described on the wiki [1]. Although, not
> in the most obvious place.
>
> I would prefer to see this kind of documentation on the wiki page
> under "Porting Xen on a new SOC".


Anything like

http://wiki.xenproject.org/wiki?title=Xen_ARM_with_Virtualization_Extensions_whitepaper&diff=16710&oldid=11342

?

Best regards

Dirk


>>
>> Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
>> ---
>> Note: I'd be happy to move this to an other documentation file if
>>        any other file fits better.
>>
>>   docs/misc/arm/booting.txt | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
>> index ffc9029..69b7d81 100644
>> --- a/docs/misc/arm/booting.txt
>> +++ b/docs/misc/arm/booting.txt
>> @@ -27,6 +27,21 @@ 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).
>>
>> +
>> +Interrupt usage
>> +===============
>> +
>> +All interrupts are taken by Xen. The function do_IRQ in Xen will
>> +dispatch the IRQ either to a guest or call a Xen specific handler.
>> +
>> +Xen handles only a limited number of interrupt:
>> +* timers
>> +* UART
>> +* SMMU
>> +
>> +The rest is either routed to guests or blacklisted by Xen.
>> +
>> +
>>   [1] linux/Documentation/arm/Booting
>>   Latest version:
>> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
>>
>>
>>
>
> Regards,
>
> [1]
> http://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions_whitepaper
>
>


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Re: [PATCH 2/2] xen: arm64: doc: Add some details about interrupt handling

[Julien Grall]

On 25/04/16 09:56, Dirk Behme wrote:
> Hi Julien,

Hello Dirk,

> On 20.04.2016 15:26, Julien Grall wrote:
>> On 19/04/16 06:59, Dirk Behme wrote:
>>> In some mailing list discussion
>>>
>>> http://lists.xen.org/archives/html/xen-devel/2016-04/msg00214.html
>>>
>>> some details about the interrupt handling of Xen were given.
>>> Add that so it's not forgotten.
>>
>> For your information, this is described on the wiki [1]. Although, not
>> in the most obvious place.
>>
>> I would prefer to see this kind of documentation on the wiki page
>> under "Porting Xen on a new SOC".
>
>
> Anything like
>
> http://wiki.xenproject.org/wiki?title=Xen_ARM_with_Virtualization_Extensions_whitepaper&diff=16710&oldid=11342

It sounds good for me.

Regards,

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

[Julien Grall]

(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.

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

Regards,

> +
>   [1] linux/Documentation/arm/Booting
>   Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
>
>

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

[Dirk Behme]

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

[Julien Grall]

Hi Dirk,

On 22/04/2016 07:23, Dirk Behme wrote:
> On 20.04.2016 15:21, Julien Grall wrote:
>> 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

Thank you, I will look at it soon.

>
>> 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?

Oh yes. sorry I would have thought the register would be exposed RO to EL2.

Regards,

-- 
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