Re: [XEN PATCH] xen/arm: Hide Pointer Authentication (PAC)

[Vladimir Murzin <vladimir.murzin@xxxxxxx>]

On 1/20/21 5:44 PM, Julien Grall wrote:
> Hi Vladimir,
> 
> On 20/01/2021 11:27, Vladimir Murzin wrote:
>> The ARMv8.3 Pointer Authentication extension is not supported by Xen
>> at the moment, so do not expose that via ID register.
>>
>> Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
>> Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>> ---
>>   xen/arch/arm/cpufeature.c        |  6 +++++
>>   xen/include/asm-arm/cpufeature.h | 38 +++++++++++++++++++++++++++++++-
>>   2 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
>> index 99fe4db28..1d8878380 100644
>> --- a/xen/arch/arm/cpufeature.c
>> +++ b/xen/arch/arm/cpufeature.c
>> @@ -187,6 +187,12 @@ static int __init create_guest_cpuinfo(void)
>>         /* Hide MTE support as Xen does not support it */
>>       guest_cpuinfo.pfr64.mte = 0;
>> +
>> +    /* Hide PAC support as Xen does not support it */
>> +    guest_cpuinfo.isa64.apa = 0;
>> +    guest_cpuinfo.isa64.api = 0;
>> +    guest_cpuinfo.isa64.gpa = 0;
>> +    guest_cpuinfo.isa64.gpi = 0;
>>   #endif
>>         /* Hide AMU support */
>> diff --git a/xen/include/asm-arm/cpufeature.h 
>> b/xen/include/asm-arm/cpufeature.h
>> index c6e5711b2..43135abef 100644
>> --- a/xen/include/asm-arm/cpufeature.h
>> +++ b/xen/include/asm-arm/cpufeature.h
>> @@ -212,8 +212,44 @@ struct cpuinfo_arm {
>>           };
>>       } mm64;
>>   -    struct {
>> +    union {
>>           uint64_t bits[2];
>> +        struct {
>> +            /* ISAR0 */
>> +            unsigned long __res0:4;
>> +            unsigned long aes:4;
>> +            unsigned long sha1:4;
>> +            unsigned long sha2:4;
>> +            unsigned long crc32:4;
>> +            unsigned long atomic:4;
>> +            unsigned long __res1:4;
>> +            unsigned long rdm:4;
>> +            unsigned long sha3:4;
>> +            unsigned long sm3:4;
>> +            unsigned long sm4:4;
>> +            unsigned long dp:4;
>> +            unsigned long fhm:4;
>> +            unsigned long ts:4;
>> +            unsigned long tlb:4;
>> +            unsigned long rndr:4;
>> +
>> +            /* ISAR1 */
>> +            unsigned long dpb:4;
>> +            unsigned long apa:4;
>> +            unsigned long api:4;
>> +            unsigned long jscvt:4;
>> +            unsigned long fcma:4;
>> +            unsigned long lrcpc:4;
>> +            unsigned long gpa:4;
>> +            unsigned long gpi:4;
>> +            unsigned long frintts:4;
>> +            unsigned long sb:4;
>> +            unsigned long specres:4;
>> +            unsigned long bf16:4;
>> +            unsigned long dgh:4;
>> +            unsigned long i8mm:4;
>> +            unsigned long __res0:8;
> 
> This unfortunately break the build on arm64 becase __res0 is defined twiced 
> in the structure:
> 
> oss/xen/xen/include/asm/cpufeature.h:251:27: error: duplicate member ‘__res0’
>              unsigned long __res0:8;
>                            ^~~~~~
> 

Sorry about that, I should have double checked that patch still compiles.

> The change is trivial, so I have resolved it (see change below) and committed 
> it:
> 
> diff --git a/xen/include/asm-arm/cpufeature.h 
> b/xen/include/asm-arm/cpufeature.h
> index 2baf7919615d..70cb67301f74 100644
> --- a/xen/include/asm-arm/cpufeature.h
> +++ b/xen/include/asm-arm/cpufeature.h
> @@ -248,7 +248,7 @@ struct cpuinfo_arm {
>              unsigned long bf16:4;
>              unsigned long dgh:4;
>              unsigned long i8mm:4;
> -            unsigned long __res0:8;
> +            unsigned long __res2:8;
>          };
>      } isa64;
> 

LGTM, Great Thanks!

Vladimir

> Cheers,
>