[U-Boot] [PATCH v4 2/9] efi_loader: AArch64: Run EFI payloads in EL2 if U-Boot runs in EL3

[Alexander Graf]

On 22.06.16 04:50, Prabhakar Kushwaha wrote:
> Hi Alex
> 
>> -----Original Message-----
>> From: Alexander Graf [mailto:agraf at suse.de]
>> Sent: Tuesday, June 21, 2016 4:37 AM
>> To: u-boot at lists.denx.de
>> Cc: york sun <york.sun at nxp.com>; Prabhakar Kushwaha
>> <prabhakar.kushwaha at nxp.com>
>> Subject: [PATCH v4 2/9] efi_loader: AArch64: Run EFI payloads in EL2 if U-
>> Boot runs in EL3
>>
>> Some boards decided not to run ATF or other secure firmware in EL3, so they
>> instead run U-Boot there. The uEFI spec doesn't know what EL3 is though - it
>> only knows about EL2 and EL1. So if we see that we're running in EL3, let's get
>> into EL2 to make payloads happy.
>>
>> Signed-off-by: Alexander Graf <agraf at suse.de>
>> ---
> 
> <snip>
> 
>>  	asm volatile("isb");
>> diff --git a/cmd/bootefi.c b/cmd/bootefi.c index 2169065..edd0980 100644
>> --- a/cmd/bootefi.c
>> +++ b/cmd/bootefi.c
>> @@ -205,6 +205,17 @@ static unsigned long do_bootefi_exec(void *efi, void
>> *fdt)
>>  		loaded_image_info.device_handle = nethandle;  #endif
>>
>> +#ifdef CONFIG_ARM64
>> +	/* On AArch64 we need to make sure we call our payload in < EL3 */
>> +	if (current_el() == 3) {
>> +		smp_kick_all_cpus();
>> +		dcache_disable();	/* flush cache before switch to EL2 */
>> +		armv8_switch_to_el2();
>> +		/* Enable caches again */
>> +		set_sctlr(get_sctlr() | (CR_C|CR_M));
>> +	}
> 
> As exception level switch to EL2. Who is creating MMU table for EL2.

It just reuses the same page tables that EL3 was using. As York already
mentioned, that shouldn't have worked, but does :).


Alex