From: Christoph Hellwig<hch@xxxxxx>Looks that dead code has been there since intel-iommu driver was
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<hch@xxxxxx>
But someone might really want to take a look if draining makes sense here
or not.
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.