Subject: [PATCH v2 20/21] arm64: VHE: Add support for running Linux in EL2 mode

From: [email-masked] (Suzuki K. Poulose)
Date: Tue, 26 Jan 2016 14:30:13 +0000

On 26/01/16 14:04, Suzuki K. Poulose wrote:
> On 25/01/16 15:53, Marc Zyngier wrote:
>> With ARMv8.1 VHE, the architecture is able to (almost) transparently
>> run the kernel at EL2, despite being written for EL1.
>>
>> This patch takes care of the "almost" part, mostly preventing the kernel
>> from dropping from EL2 to EL1, and setting up the HYP configuration.
>
>>   #ifdef CONFIG_COMPAT
>> @@ -521,6 +542,15 @@ CPU_LE(    movk    x0, #0x30d0, lsl #16    )    // Clear EE and E0E on LE systems
>>       /* Stage-2 translation */
>>       msr    vttbr_el2, xzr
>>
>> +    cbz    x2, install_el2_stub
>
> Though it is apparent, may be its worth adding a comment here that we don't drop to EL1 here ?
>
>> +
>> +    setup_vtcr x4, x5
>> +
>> +    mov    w20, #BOOT_CPU_MODE_EL2        // This CPU booted in EL2
>> +    isb
>> +    ret
>
>> +
>> +install_el2_stub:
>
> And a comment here mentioning, install the hyp stub and drops to EL1 ?

Also, the comments around el2_setup invocation still says, Drop to EL1 which may
need to be updated.

Cheers
Suzuki