Re: [PATCH v3 3/4] hw/block/nvme: Fix pmrmsc register size

[Andrzej Jakowski <andrzej.jakowski@linux.intel.com>]

On 6/30/20 9:45 AM, Klaus Jensen wrote:
> On Jun 30 17:16, Philippe Mathieu-Daudé wrote:
>> On 6/30/20 5:10 PM, Andrzej Jakowski wrote:
>>> On 6/30/20 4:04 AM, Philippe Mathieu-Daudé wrote:
>>>> The Persistent Memory Region Controller Memory Space Control
>>>> register is 64-bit wide. See 'Figure 68: Register Definition'
>>>> of the 'NVM Express Base Specification Revision 1.4'.
>>>>
>>>> Fixes: 6cf9413229 ("introduce PMR support from NVMe 1.4 spec")
>>>> Reported-by: Klaus Jensen <k.jensen@samsung.com>
>>>> Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
>>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>> ---
>>>> Cc: Andrzej Jakowski <andrzej.jakowski@linux.intel.com>
>>>> ---
>>>>  include/block/nvme.h | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/block/nvme.h b/include/block/nvme.h
>>>> index 71c5681912..82c384614a 100644
>>>> --- a/include/block/nvme.h
>>>> +++ b/include/block/nvme.h
>>>> @@ -21,7 +21,7 @@ typedef struct QEMU_PACKED NvmeBar {
>>>>      uint32_t    pmrsts;
>>>>      uint32_t    pmrebs;
>>>>      uint32_t    pmrswtp;
>>>> -    uint32_t    pmrmsc;
>>>> +    uint64_t    pmrmsc;
>>>>  } NvmeBar;
>>>>  
>>>>  enum NvmeCapShift {
>>>> -- 2.21.3
>>>
>>> This is good catch, though I wanted to highlight that this will still 
>>> need to change as this register is not aligned properly and thus not in
>>> compliance with spec.
>>
>> I was wondering the odd alignment too. So you are saying at some time
>> in the future the spec will be updated to correct the alignment?
Yep I think so.
So PMRMSC currently is 64-bit register that is defined at E14h offset.
It is in conflict with spec because spec requires 64-bit registers to 
be 64-bit aligned.
I anticipate that changes will be needed.

>>
>> Should we use this instead?
>>
>>       uint32_t    pmrmsc;
>>  +    uint32_t    pmrmsc_upper32; /* the spec define this, but *
>>  +                                 * only low 32-bit are used  */
>>
>> Or eventually an unnamed struct:
>>
>>  -    uint32_t    pmrmsc;
>>  +    struct {
>>  +        uint32_t pmrmsc;
>>  +        uint32_t pmrmsc_upper32; /* the spec define this, but *
>>  +                                  * only low 32-bit are used  */
>>  +    };
>>
>>>
>>> Reviewed-by Andrzej Jakowski <andrzej.jakowski@linux.intel.com>
>>>
>>
> 
> I'm also not sure what you mean Andrzej. The odd alignment is exactly
> what the spec (v1.4) says?
>