[PATCH][for-stable-v5.11]] arm64: Unconditionally set virtual cpu id registers

[Vladimir Murzin]

Hi Marc,

On 3/16/21 1:22 PM, Marc Zyngier wrote:
> Hi Vladimir,
> 
> On Tue, 16 Mar 2021 11:25:00 +0000,
> Vladimir Murzin <vladimir.murzin at arm.com> wrote:
>>
>> Commit 78869f0f0552 ("arm64: Extract parts of el2_setup into a macro")
>> reorganized el2 setup in such way that virtual cpu id registers set
>> only in nVHE, yet they used (and need) to be set irrespective VHE
>> support. Lack of setup causes 32-bit guest stop booting due to MIDR
>> stay undefined.
> 
> Surely this affects 64bit guests as well, doesn't it? I guess the
> 32bit code tries to infer stuff such as the architecture revision from
> MIDR and falls over, and that the 64bit Linux code has less baggage?

Correct, that affects all guests, yet 32-bit tries to lookup processor type
so it is how it became visible to me

> 
>>
>> Fixes: 78869f0f0552 ("arm64: Extract parts of el2_setup into a macro")
>> Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
>> ---
>>
>> There is no upstream fix since issue went away due to code there has
>> been reworked in 5.12: nVHE comes first, so virtual cpu id register
>> are always set.
>>
>> Maintainers, please, Ack.
>>
>>  arch/arm64/include/asm/el2_setup.h | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
>> index f988e94cdf9e..db87daca6b8c 100644
>> --- a/arch/arm64/include/asm/el2_setup.h
>> +++ b/arch/arm64/include/asm/el2_setup.h
>> @@ -113,7 +113,7 @@
>>  .endm
>>  
>>  /* Virtual CPU ID registers */
>> -.macro __init_el2_nvhe_idregs
>> +.macro __init_el2_idregs
>>  	mrs	x0, midr_el1
>>  	mrs	x1, mpidr_el1
>>  	msr	vpidr_el2, x0
>> @@ -165,6 +165,7 @@
>>  	__init_el2_stage2
>>  	__init_el2_gicv3
>>  	__init_el2_hstr
>> +	__init_el2_idregs
>>  
>>  	/*
>>  	 * When VHE is not in use, early init of EL2 needs to be done here.
>> @@ -173,7 +174,6 @@
>>  	 * will be done via the _EL1 system register aliases in __cpu_setup.
>>  	 */
>>  .ifeqs "\mode", "nvhe"
>> -	__init_el2_nvhe_idregs
>>  	__init_el2_nvhe_cptr
>>  	__init_el2_nvhe_sve
>>  	__init_el2_nvhe_prepare_eret
> 
> The couple of VHE systems I have around don't suffer from this issue,
> but it looks like I can trigger it on the FVP model (probably because
> the model is nasty enough to not have VPIDR_EL2 default to anything
> sensible!).

Well firmware could easily hide the issue if it set registers for us ;)

> 
> Anyway, good catch. If you can respin it to drop the reference to
> 32bit guests, I'll happily ack it!

Thanks for prompt review! I'll re-spin it shortly.

Vladimir

> 
> Thanks,
> 
> 	M.
>