Re: [PATCH] dmaengine: idxd: Change wmb() to smp_wmb() when copying completion record to user space

[Dave Hansen]

On 1/30/24 11:53, Boqun Feng wrote:
>>> Fixes: b022f59725f0 ("dmaengine: idxd: add idxd_copy_cr() to copy user completion record during page fault handling")
>>> Suggested-by: Nikhil Rao <nikhil.rao@xxxxxxxxx>
>>> Tested-by: Tony Zhu <tony.zhu@xxxxxxxxx>
> Since it has a "Fixes" tag and a "Tested-by" tag, I'd assume there has
> been a test w/ and w/o this patch showing it can resolve a real issue
> *constantly*? If so, I think x86 might be broken somewhere.
> 
> [Cc x86 maintainers]

Fenghua, could you perhaps explain how this problem affects end users?
What symptom was observed that made it obvious something was broken and
what changes with this patch?