Re: [Xen-devel] [RFC PATCH V2 1/2] xen-pt: bind/unbind interrupt remapping format MSI

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

On 2017年05月19日 20:04, Jan Beulich wrote:
>>>> On 19.05.17 at 13:16, <anthony.perard@xxxxxxxxxx> wrote:
>> On Thu, May 18, 2017 at 01:32:59AM -0400, Lan Tianyu wrote:
>>> --- a/include/hw/i386/apic-msidef.h
>>> +++ b/include/hw/i386/apic-msidef.h
>>> @@ -26,6 +26,7 @@
>>>  
>>>  #define MSI_ADDR_DEST_ID_SHIFT          12
>>>  #define MSI_ADDR_DEST_IDX_SHIFT         4
>>> -#define  MSI_ADDR_DEST_ID_MASK          0x00ffff0
>>> +#define  MSI_ADDR_DEST_ID_MASK          0x000fff00
>> The value of MSI_ADDR_DEST_ID_MASK is changed here. I think the patch
>> should be:
>> +#define  MSI_ADDR_DEST_ID_MASK          0x000ffff0
> Judging from other sources, rather the other way around - the
> mask needs to have further bits removed (should be 0x000ff000
> afaict). Xen sources confirm this, and while Linux has the value
> you suggest, that contradicts
Agree. Defining the mask as "0x000ff000" makes more sense.
Just check Qemu source code. Only apic_send_msi() and msi_dest_id() use
the mask
to get dest apic id. They mask MSI address field with 
MSI_ADDR_DEST_ID_MASK and
then right-shift 12bit. The low 12bit won't be used.

Anthony, does this make sense?

-- 
Best regards
Tianyu Lan


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