> From: Thomas Monjalon [mailto:tho...@monjalon.net] > Sent: Monday, 20 February 2023 16.41 > > 20/02/2023 16:35, Bruce Richardson: > > On Mon, Feb 20, 2023 at 04:30:20PM +0100, Thomas Monjalon wrote: > > > 20/02/2023 16:07, Morten Brørup: > > > > With the new viewing angle, the current define RTE_IOVA_AS_PA > makes more sense to me now than before. So we should probably stick > with it, rather than introduce something that might confuse developers > who already have the same viewing angle. > > > > > > > > But it still seems counterintuitive to me that disabling some > feature ("enable_iova_as_pa") is not supported throughout DPDK; the > logic seems inverted. Apparently, it also makes it difficult to assign > good titles to patches that support disabling such a feature. :-) > > > > > > > > <irony> > > > > On the positive side, since everything supports this > "enable_iova_as_pa" feature, we don't need to add it to the PMD feature > list. If the logic wasn't inverted like this, the PMD feature list > should probably reflect which PMDs supported the "iova_as_va_only" > compile time option. ;-) > > > > </irony> > > > > > > That's a change I would like to do: > > > The Meson variable in the drivers should be "support_iova_as_va" > > > and would mean we can compile the driver when "enable_iova_as_pa" > is false. > > > > > All drivers (that I am aware of) support iova_as_va. What is missing > is > > drivers supporting "iova_as_va_only". Any reference to va without the > word > > "only" on it will be misleading. > > > > A third way of looking at it, is to work with the fact that the > reason > > drivers require changes to support this "va_only" mode, ro no-pa > mode, is > > due to the fact that the mbuf no longer tracks iovas and only VAs. > > Therefore, we can have a variable called "require_iova_in_mbuf", > which > > would hopefully cut through this whole va vs pa addition/subtraction > mess. > > What do you think? > > Yes "require_iova_in_mbuf" describes better the reality, > so it is simpler to understand.
Agreed. It is a good idea narrowing the scope to the concrete issue. Proceeding to also consider the source code using the corresponding #define, e.g. the rte_mbuf: https://elixir.bootlin.com/dpdk/v23.03-rc1/source/lib/mbuf/rte_mbuf_core.h#L469 Would you also change the corresponding #define from RTE_IOVA_AS_PA to RTE_REQUIRE_IOVA_IN_MBUF? Perhaps we could invert the value, e.g. "mbuf_without_iova" and #define RTE_MBUF_WITHOUT_IOVA? Intuitively, a default value of "false" better reflects that the feature is optional. PS: I don't mind if you limit this to meson, and ignore my feature creep expanding into #define land.
