On Sat, 20 May 2023 09:07:57 +0100 James Addison <j...@jp-hosting.net> wrote:
> Hi folks, > > I don't think that I should file this as a Debian bugreport, because > it's not a problem that I've experienced with Debian. > > And I don't think that it's appropriate to write to Debian developers > directly about it yet, because I haven't been able to test the results > of what I'm curious about here. > > However: my understanding is that the Geode LX is basically an i686 > CPU that lacks one instruction (a 'no operation' - noop - called > NOPL). There's a long and entertaining writeup about that here: > https://www.jookia.org/wiki/Nopl > > It's an unusual CPU and didn't see wide consumer adoption except > within the OLPC (One Laptop Per Child) project, where it was used for > two of the early laptop models (XO 1.0 and XO 1.5). I have four FIT-PC 1s (https://en.wikipedia.org/wiki/Fit-PC, https://linux-hardware.org/?probe=c256a73072). Two are in daily use with Bullseye, the other two are spares I have upgraded to Bookworm to test that. They run Geodes. It has been problematic for X support, and the kernel has only supported the temperature sensors recently. > > Recently, Intel has begun proposing some security improvements for > i686 that make use of the NOPL instruction -- and that, I think, could > cause support for the Geode LX to fall away from many Linux operating > systems because there's a fair and very reasonable argument that > adding security features for the majority of users outweighs > supporting an old and unusual CPU. > > However, to get to the point after that lengthy context: there is a > patch available on the Linux kernel mailing list that adds emulation > of NOPL instructions at the kernel level. I would be curious to know > whether anyone has tried that - I intend to, after finding some > hardware that includes a Geode LX. The patch is found at: > > https://lore.kernel.org/all/20210626130313.1283485-1-mar...@orca.pet/ I have not. I was unaware of it until I read your email. I have no great interest in trying it. > > (note: it's unclear to me whether the NOPL emulation only works for > the Linux kernel itself, or whether it extends to enabling programs > that run on the system (aka userspace binaries) that contain NOPL > instructions to run. _if_ kernel-level NOPL emulation allows both the > kernel _and_ those programs to run correctly, then I think it could be > a neat way to provide the security properties of Intel CET on most > i686 hardware, while still also allowing OLPC laptops to run the same > software (albeit with slightly reduced security properties)) > > Thanks (and I'll try to remember to update this thread with any > findings), James > The FIT-PC is hard wired to 256MB of RAM, some of which is dedicated to video RAM. Getting Bullseye installed on that was an interesting struggle. I do not intend to try it with Bookworm. I plan to upgrade the remaining two Bullseye machines to Bookworm once that is released. I will then start looking for replacements for the FIT-PCs, possibly with RISC-V processor(s). The lack of RAM is one reason. The FIT-PCs are painfully slow for interactive use, even without X. Those two concerns may be specific to the FIT-PC and not apply to other Geode computers. Also, and of greatest concern, Linux support for the i686 architecture is waning. Not just the kernel, but userland programs as well. As that support wanes, less and less testing will make the i686 architecture less secure and less stable. This will accelerate the process of abandoning i686. root@freeman:~# cat /proc/cpuinfo processor : 0 vendor_id : AuthenticAMD cpu family : 5 model : 10 model name : Geode(TM) Integrated Processor by AMD PCS stepping : 2 cpu MHz : 499.879 cache size : 128 KB physical id : 0 siblings : 1 core id : 0 cpu cores : 1 apicid : 0 initial apicid : 0 fdiv_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu de pse tsc msr cx8 sep pge cmov clflush mmx mmxext 3dnowext 3dnow cpuid 3dnowprefetch vmmcall bugs : sysret_ss_attrs spectre_v1 spectre_v2 spec_store_bypass bogomips : 999.75 clflush size : 32 cache_alignment : 32 address sizes : 32 bits physical, 32 bits virtual power management: root@freeman:~# -- Does anybody read signatures any more? https://charlescurley.com https://charlescurley.com/blog/
