Re: [Xen-devel] [PATCH] AMD IOMMU: Introduce support for IVHD block type 11h

[Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>]

Hi Jan,

On 05/19/2016 04:09 AM, Jan Beulich wrote:
> > > > >>>+int __init amd_iommu_get_supported_ivhd_type(void)
> > > > >>>+{
> > > > >>>+    if ( unlikely(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_MSI) )
> > > > >>>+        return -EPERM;
> > > >>
> > > >>This check appears out of the blue, and isn't being mentioned in
> > > >>the description. Best would probably be to split it out, but at the
> > > >>very least it needs to be (briefly) explained.
> > >
> > >This logic was actually duplicated from the
> > >amd_iommu_update_ivrs_mapping_acpi(). I believe this was added by the
> > >
> > >      commit 992fdf6f46252a459c6b1b8d971b2c71f01460f8
> > >          honor ACPI v4 FADT flags
> > >
> > >It might make more sense to pull this out to just check once in the
> > >amd_iommu_init() along with adding some explanation.
> Does it actually need duplicating? I.e. doesn't the error that results
> from amd_iommu_update_ivrs_mapping_acpi() (if the flag is clear)
> not suffice?
>
> Jan
No, it doesn't need duplicated. It was accidentally duplicated. 
Howerver, as you mentioned earlier, it probably should be moved to the 
beginning of amd_iommu_init() before any parsing of the IVRS table.
Suravee.

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