> From: Christoph Hellwig <[email protected]> > Sent: Monday, February 14, 2022 3:34 PM > > On Mon, Feb 14, 2022 at 10:57:02AM +0800, Lu Baolu wrote: > > This removes unnecessary commented code. > > Removing dead code is always good: > > Reviewed-by: Christoph Hellwig <[email protected]> > > But someone might really want to take a look if draining makes sense here > or not.
Looks that dead code has been there since intel-iommu driver was firstly introduced in 2007. I don't know whether we can dig out the reason (Baolu, can you have a check?) why it's only special cased for read draining but not write draining. I cannot find any such recommendation from VT-d spec. Looking at VT-d spec it stated that since VT-d major version 2 drain is conducted automatically by hardware and above flags are essentially ignored. Given that possibly a safer option is to always set read/write draining flags before version 2 and skip it after. Thanks Kevin _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
