Re: Questions regarding the still unpublished qemu series https://github.com/yiliu1765/qemu/tree/zhenzhong/wip/iommufd_nesting_rfcv1

[Joel Granados]

On Thu, Dec 21, 2023 at 03:33:47AM +0000, Duan, Zhenzhong wrote:
> Hi Joel,
> 
> >-----Original Message-----
> >From: Joel Granados <j.granados@samsung.com>
> >Subject: Questions regarding the still unpublished qemu series
> >https://github.com/yiliu1765/qemu/tree/zhenzhong/wip/iommufd_nesting
> >_rfcv1
> >
> >Hello Everyone
> >
> >While running
> >https://github.com/yiliu1765/qemu/tree/zhenzhong/wip/iommufd_nesting
> >_rfcv1
> >I have come across particular code path that seems odd:
> >
> >I'm hitting an assert in softmmu/memory.c:1994 after calling a
> >notification from vtd_flt_page_walk_level. The code in memory.c:1994
> >makes sure that when type==IOMMU_NOTIFIER_UNMAP, the permissions
> >are
> >IOMMU_NONE. But the code in vtd_flt_page_walk_level sets the
> >permissions to read|write. This is part of the "intel_iommu: piotlb
> >invalidation should notify unmap" commit in the iommufd_nesting_rfcv1
> >series.
> >
> >Question is: Why assert on the permissions being NONE if they might be
> >read|write?
> >
> >Hope this makes sense. Don't hesitate to get back to me if you see that
> >there is something missing in my explanation.
> 
> Thanks for your report, you are right. We had seen the same issue with
> vhost device and have it fixed internally. Did you also use a vhost device
> or not?
> 
> The link you used is a bit old, could you try with 
> https//:github.com/yiliu1765/qemu/commits/zhenzhong/iommufd_nesting_rfcv1/
I thought it was the same branch, but I see that it does not have the
"wip" in the path.

Great!. I'll try this as soon as I get some free cycles (they are
difficult to find in holiday season:) and get back to you if I run into
anything else.

Thx for the link.

Best

> 
> Thanks
> Zhenzhong

-- 

Joel Granados

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