On April 30, 2025 thus sayeth Bryan Brattlof: > On April 30, 2025 thus sayeth Tom Rini: > > On Wed, Apr 30, 2025 at 10:56:27PM +0530, Raghavendra, Vignesh wrote: > > > > > > > > > On 4/30/2025 10:01 PM, Tom Rini wrote: > > > > On Wed, Apr 30, 2025 at 11:29:04AM -0500, Bryan Brattlof wrote: > > > >> On April 30, 2025 thus sayeth Anshul Dalal: > > > >>> As discussed here[1], the go command causes undefined behavior when > > > >>> used > > > >>> for running custom OSes since the icache might hold outdated data. > > > >>> OSes > > > >>> usually also expect the MMU to be disabled upon execution. > > > >>> > > > >>> Therefore this patch adds a call to cleanup_before_linux before we > > > >>> jump > > > >>> to the loaded program/os which disables both the caches and the MMU. > > > >>> This makes the go command's behavior consistent with riscv platforms. > > > >>> > > > >> > > > >> I know quite a few other OSes are beginning to use U-Boot (QNX, > > > >> GreenHills or all the other RTOSes) each with their own requirements > > > >> from the bootloader. I'm curious if we should make boot* a little more > > > >> generic rather than abuse the 'go' command. > > > > > > VXworks has its own: > > > https://docs.u-boot.org/en/stable/usage/os/vxworks.html > > > > > > I suppose QNX and others should ideally have their own cmds as needed. > > > > Well, what's the QNX output file format (options?) again? > > I've only ever seen outputs in compressed binary formats but I've been > told there are tools to produce an ELF for the simulators >
Ah as soon as I hit send I find it in the QNX docs[0] it's their own IFS format :) [0] https://www.qnx.com/developers/docs/7.1/#com.qnx.doc.neutrino.building/topic/intro/intro_ifs.html > > > > > > Well, that's what bootelf is for :) > > > > > > > > > > And if its not an elf but some .bin file "go" cmd should be used in > > > conjunction with "cache" cmd here to flush/disable cache, I guess? > > > > Well, what exactly are we talking about? Is this an "in theory" or some > > project(s) which exist today? > > > > I noticed this thread mainly because of the number of RTOS people asking > me about low level stuff U-Boot and TF-A is doing. I haven't seen any > 'In-Production' type bugs but I wouldn't be surprised if U-Boot is being > used in their CI environments today. > > ~Bryan > > > There's a whole lot of reasons for either a legacy header and bootm or a > > not-legacy FIT image. The "go" command is for the "U-Boot is a debugger" > > side of the world, not how you should kick off some OS/application in > > production. It is all of the "this is dangerous" idioms. > > > > > If so, we should probably update the docs for this cmd appropriately so > > > as to avoid end users overloading like what RISC-V did? > > > > Yes, we should clarify things as needed and unwind, most likely, what > > RISC-V is doing. But not blindly so as perhaps there's now, sigh, a > > production / in-the-wild case here and we're now in a sticky spot. > > > > I like the idea of boot${OS} flags if only to standardize the interface > of how each OS should boot. I worry about situation where custom > scripting is being used to boot in production rather than stdboot > > ~Bryan
