Re: [edk2-devel] [PATCH 1/1] EmbeddedPkg/NonCoherentIoMmuDxe: Make SetAttributes always succeed

["Leif Lindholm" <quic_llindhol@quicinc.com>]

On 2024-03-12 09:58, Ard Biesheuvel wrote:
> On Tue, 12 Mar 2024 at 17:56, Leif Lindholm <quic_llindhol@quicinc.com> wrote:
>>
>> On 2024-03-12 09:50, Ard Biesheuvel wrote:
>>> On Tue, 12 Mar 2024 at 17:38, Leif Lindholm <quic_llindhol@quicinc.com> wrote:
>>>>
>>>> On 2024-03-12 08:17, Ard Biesheuvel wrote:
>>>>> From: Ard Biesheuvel <ardb@kernel.org>
>>>>>
>>>>> NonCoherentIoMmuSetAttribute() does nothing except return
>>>>> EFI_UNSUPPORTED. This was fine when it was introduced, but now, the PCI
>>>>> bus driver will fail a PCI I/O Map() operation if the SetAttributes
>>>>> fails.
>>>>>
>>>>> So return EFI_SUCCESS instead.
>>>>
>>>> It's unclear to me why this change is safe (looking forward).
>>>> Does NonCoherentIoMmuDxe also imply no IoMmu actually exists?
>>>>
>>>
>>> Basically. NonCoherentIoMmuDxe is just a vehicle to allow
>>> NonCoherentDmaLib to be plugged into the PCI host bridge driver. It is
>>> not intended to ever do anything more than that.
>>
>> Not that it needs to happen for this
>> (Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>)
>> but maybe we ought to consider renaming it then?
>> DummyIoMmuDxe?
> 
> Fair point. Or PassThroughIoMmuDxe perhaps?

Works for me.
Or, hmm...
Is there a risk that sounds a bit like a driver that actively configures 
IoMmus into passthrough mode?

/
     Leif



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