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

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, May 23, 2017 at 08:16:25PM +0800, Lan Tianyu wrote:
> 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?

Yes, it does.
The change to MSI_ADDR_DEST_ID_MASK should probably go in its own patch.

-- 
Anthony PERARD

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