Messages in this thread | | | Date | Mon, 26 Feb 2024 21:29:59 +0000 | From | Conor Dooley <> | Subject | Re: [PATCH] riscv: deprecate CONFIG_MMU=n |
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On Mon, Feb 26, 2024 at 11:00:41AM -0800, Charles Lohr wrote: > WOAH! Please DO NOT deprecate NOMMU. I use the NOMMU build constantly > and NOMMU Linux on RISC-V is the avenue used by many FPGA soft cores > for Linux, as well as some limited systems. > > I get new copies of the kernel when there are releases and test them > frequently to make sure everything is still working as expected.
That is great - it is good to know that people are actively testing. I was aware that a lot of the soft core folks did run nommu kernels (and I know some do use XIP also) but everything I ever saw was running on old kernels (5.x).
> On Mon, Feb 26, 2024 at 8:03 AM Conor Dooley <conor@kernel.org> wrote: > > > > On Mon, Feb 26, 2024 at 04:25:24PM +0100, Clément Léger wrote: > > > I guess I could also mark XIP as deprecated. > > > > I'm not so sure, people recently added XIP support to QEMU (and sent > > kernel fixes in December). XIP is also not nearly as much of a problem > > to support, there's far less that it does differently, the main barrier > > was the inability to test it which is no longer the case. > > That said, XIP is gonna kill itself off I feel as it does not support > > runtime patching and therefore is extremely limited on extensions, given > > we use alternatives for all of that (although I suppose if someone has a > > usecase they could make nasty macros worse and implement a compiletime > > switch in the alternatives too).
> For us we just don't care about XIP. I mean if someone did push it > through to fruition, I'd also test and use it, but I urge you please > do not deprecate this.
XIP does work. What I was talking about here was supporting something "fancier" than rv{32,64}imafdc.
> While it's sometimes needed a bit of a > creative build to get everything working, I've never needed to patch > anything in the kernel beyond patching in a custom console for serial > output. > > I am happy to discuss the possibility of me and or one of the other > RISC-V soft (FPGA) core people stepping up to try to be more active, > but so far we've just been very well serviced by the current NOMMU > Linux setup.
Most of the issues aren't with nommu actually working, it is the extra effort in development as it has to be accounted for. I would estimate that 2/3 of the build issues I report on this list are nommu. The best thing that you can do to ensure support for things you use is: a) scream when someone wants to remove it b) actively let people know you're using it
Seems like you're doing a) but maybe getting someone that provides Tested-bys whenever you test the releases would be good.
Cheers, Conor.
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