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Re: [Xen-devel] [PATCH 0/2] Dangling fixes for ARM iommu





On 1/22/19 1:48 PM, Andrii Anisov wrote:
Hello Julien,

Hi,

On 21.01.19 19:29, Julien Grall wrote:
(+ Juergen)
All patches candidate for Xen 4.12 should have the release manager CCed and explain the pros/cons to have those patches for this release. It is also useful if you add for-4.12 (or similar) in the [...] so we can prioritize it.

I've got the point. Thank you for adding Juergen.

Indeed code base evolved, for instance iommu_use_hap_pt has a slight different behavior now.

Actually you properly pointed the problem. I'm not sure how it happened, because I did test build and run for those patches yesterday. But now, progressing with our stuff porting, I realized that the patch 1 is missing dependency on `xen/sched.h` required by `iommu_use_hap_pt`.

So please stripped my RB
OK.

The AB is arguable as it is quite old.
I could drop it for v2.

Yes please. But see below.


Secondly, it often happens that some patches have the required acked-by and reviewed-by but are not merged because they makes little sense without the rest of the series.

Yes, sure, but fixes are still relevant and are quite autonomous. The only relation to the series is that they were discovered during its implementation.

A fix would be if you found a bug in a configuration that we are meant to support.


In that case, the current code base does not support the case where the P2M is not shared with the IOMMU and does not support new IOMMU bindings in the current setup.

It is the intention of the rest of the series.

The rest of series is not ready and not targeting 4.12. So why should we get them merged?


So I am not convinced they should be included in Xen 4.12 or even without the rest of the series.
IMO, the pure fixes, like patch 2, and the first hunk of patch 1 should be OK for 4.12.

The first hunk of patch 1 aside, we never supported the new IOMMU bindings nor unsharing the P2M. So what do you actually fix?

Supporting unshared P2M will require more work given because the code relies on mfn_to_gmfn that is not implemented on Arm. So accepting this patch standalone would be misleading as the rest of the series is not going to be merged in Xen 4.12.

Similarly, we don't support new IOMMU bindings. The patch #2 alone is going to add more trouble as now Dom0 would not be able to use the IOMMU if it were not hidden.

So I still question the usefulness of those 2 patches outside of the series.

Cheers,

--
Julien Grall

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