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Date:   Tue, 28 Nov 2023 20:57:15 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Nicolin Chen <nicolinc@nvidia.com>
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Subject: Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE
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On Tue, Nov 28, 2023 at 04:51:21PM -0800, Nicolin Chen wrote:
> > > I also thought about making this out_driver_error_code per HW.
> > > Yet, an error can be either per array or per entry/quest. The
> > > array-related error should be reported in the array structure
> > > that is a core uAPI, v.s. the per-HW entry structure. Though
> > > we could still report an array error in the entry structure
> > > at the first entry (or indexed by "array->entry_num")?
> > >
> > 
> > why would there be an array error? array is just a software
> > entity containing actual HW invalidation cmds. If there is
> > any error with the array itself it should be reported via
> > ioctl errno.
> 
> User array reading is a software operation, but kernel array
> reading is a hardware operation that can raise an error when
> the memory location to the array is incorrect or so.

Well, we shouldn't get into a situation like that.. By the time the HW
got the address it should be valid.

> With that being said, I think errno (-EIO) could do the job,
> as you suggested too.

Do we have any idea what HW failures can be generated by the commands
this will execture? IIRC I don't remember seeing any smmu specific
codes related to invalid invalidation? Everything is a valid input?

Can vt-d fail single commands? What about AMD?

> > Jason, how about your opinion? I didn't spot big issues
> > except this one. Hope it can make into 6.8.

Yes, lets try

Jason