Hi, Just to note, some PMDs do not use physical address field at all. As an example - mlx5 PMD (and it is far from being the only one) could take an advantage from this patch. Nonetheless, I tend to agree - for the whole DPDK framework it looks risky. I had the similar thoughts about removing iova field and I did not dare to propose 😊
With best regards, Slava > -----Original Message----- > From: Olivier Matz <olivier.m...@6wind.com> > Sent: Friday, July 1, 2022 12:49 > To: Bruce Richardson <bruce.richard...@intel.com> > Cc: Shijith Thotton <sthot...@marvell.com>; jer...@marvell.com; NBU- > Contact-Thomas Monjalon (EXTERNAL) <tho...@monjalon.net>; dev@dpdk.org > Subject: Re: [PATCH] mbuf: add mbuf physical address field to dynamic > field > > Hi, > > On Thu, Jun 30, 2022 at 05:55:21PM +0100, Bruce Richardson wrote: > > On Thu, Jun 30, 2022 at 09:55:16PM +0530, Shijith Thotton wrote: > > > If all devices are configured to run in IOVA mode as VA, physical > > > address field of mbuf (buf_iova) won't be used. In such cases, > > > buf_iova space is free to use as a dynamic field. So a new dynamic > > > field member > > > (dynfield2) is added in mbuf structure to make use of that space. > > > > > > A new mbuf flag RTE_MBUF_F_DYNFIELD2 is introduced to help identify > > > the mbuf that can use dynfield2. > > > > > > Signed-off-by: Shijith Thotton <sthot...@marvell.com> > > > --- > > I disagree with this patch. The mbuf should always record the iova of > > the buffer directly, rather than forcing the drivers to query the EAL > mode. > > This will likely also break all vector drivers right now, as they are > > sensitive to the mbuf layout and the position of the IOVA address in > > the buffer. > > I have the same opinion than Stephen and Bruce. This field is widely > used in DPDK, I don't think it is a good idea to disable it if some > conditions are met.
