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

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?


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.


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