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Re: [Xen-devel] [PATCH v2] xen: arm: doc: Add firmware requirements

Hi Dirk,

On 22/04/16 07:15, Dirk Behme wrote:
Add a section about what the firmware should do in EL3 before starting Xen.

E.g. on ARM Linux the HVC instruction is used to trap into Xen. As this

I would rather say "E.g guest will use HVC instruction to issue hypercall".

can be set only at EL3, i.e. outside from Xen, document this boot requirement.

s/outside from/outside/

Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
  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 9802e5e..b0ff305 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -23,6 +23,21 @@ The exceptions to this on 32-bit ARM are as follows:

  There are no exception on 64-bit ARM.

+Firmware/bootloader requirements
+Xen relies on some settings the firmware has to do in EL3 before starting

I would replace "do" by "configure".

+* EL2: Xen must be entered in NS EL2 mode

I would drop "EL2: " as it's not clear what it stands for. Same for "HCE:" below.

+* HCE: It has to be ensured that the Secure Configuration Register
+       has the HVC instructions enabled at EL1 and above
+       ARM32: SCR.HCE == 1
+       ARM64: SCR_EL3.HCE == 1

I would simplify the description: "The bit SCR_EL3.HCR (resp. SCR.HCE for 32-bit ARM) must be set to 1."

  [1] linux/Documentation/arm/Booting
  Latest version: 


Julien Grall

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