Re: [Qemu-devel] [PATCH v1 1/6] memory: allow memory_region_register_iommu_notifier() to fail

[Auger Eric <eric.auger@redhat.com>]

Hi Peter,

On 9/16/19 5:23 AM, Peter Xu wrote:
> On Fri, Sep 13, 2019 at 10:36:10AM +0200, Eric Auger wrote:
>> Currently, when a notifier is attempted to be registered and its
>> flags are not supported (especially the MAP one) by the IOMMU MR,
>> we generally abruptly exit in the IOMMU code. The failure could be
>> handled more nicely in the caller and especially in the VFIO code.
>>
>> So let's allow memory_region_register_iommu_notifier() to fail as
>> well as notify_flag_changed() callback.
>>
>> All sites implementing the callback are updated. This patch does
>> not yet remove the exit(1) in the intel_iommu and amd_iommu code.
> 
> The idea looks sane to me, though how about using "Error **" instead
> of returning int (or, both)?  Just like the majority of rest of QEMU.
None of the memory_region_register_iommu_notifier callsites would really
use the Error object and pass it up. I am a bit reluctant to add it if
not really used. There are still plenty of functions in the memory API
that do not use any Error handle. Anyway I will follow recommendations
if there is a consensus.

Thanks

Eric
> 
> Regards,
>