Re: [Xen-devel] [PATCH] vm_event: Implement ARM SMC events

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 04/12/16 07:31, Jan Beulich wrote:
>>>> Tamas K Lengyel <tamas@xxxxxxxxxxxxx> 04/11/16 9:47 PM >>>
>> --- a/xen/include/public/vm_event.h
>> +++ b/xen/include/public/vm_event.h
>> @@ -166,6 +166,31 @@ struct vm_event_regs_x86 {
>      >uint32_t _pad;
>  >};
>  >
>> +struct vm_event_regs_arm {
>> +    uint32_t r0;
>> +    uint32_t r1;
>> +    uint32_t r2;
>> +    uint32_t r3;
>> +    uint32_t r4;
>> +    uint32_t r5;
>> +    uint32_t r6;
>> +    uint32_t r7;
>> +    uint32_t r8;
>> +    uint32_t r9;
>> +    uint32_t r10;
>> +    uint32_t r11;
>> +    uint32_t r12;
>> +
>> +    uint32_t sp; /* r13 - SP: Valid for Hyp. frames only, o/w banked (see 
>> below) */
>> +    uint32_t lr; /* r14 - LR: Valid for Hyp. Same physical register as 
>> lr_usr. */
>> +
>> +    uint32_t cpsr; /* Return mode */
>> +    uint64_t pc;
> 
> Why uint64_t instead of uint32_t?
> 
>> +    uint64_t ttbr0;
>> +    uint64_t ttbr1;
>> +    uint32_t _pad;
>> +};
> 
> This padding field is pretty strange: Without the adjustment to pc there are 
> 16
> 32-bit fields (not counting the padding one), so I don't see why padding 
> would be
> needed at all. And with pc adjusted the padding field would surely better go
> ahead of the two remaining 64-bit ones.
> 
>> @@ -254,6 +279,7 @@ typedef struct vm_event_st {
>      >union {
>          >union {
>              >struct vm_event_regs_x86 x86;
>> +            struct vm_event_regs_arm arm;
>          >} regs;
>  
>          Does this alter the x86 ABI? Perhaps the ARM structure is small 
> enough for
> this to not happen now, but what's the general idea about not breaking other
> arch'es ABIs when adding support for a new arch here?

I'd suggest modifying VM_EVENT_INTERFACE_VERSION whenever that becomes
the case.


Thanks,
Razvan

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