[Trisquel-devel] RISCV T-Head CPU bug and Trisquel riscv64 port

[Jing Luo]

Hello all,

About two days ago, researchers published a sever CPU bug "ghostwrite" 
in T-Head C910 and C920 CPU's vector extension. The CPU bug is 
unpatchable by software, allows arbitrary memory write of *physical 
address*. The only work around is to disable the vector extension in the 
device tree (?), but with a significant performance penalty of 30~%.

https://ghostwriteattack.com/riscvuzz.pdf

I was going to buy the Milk-V Pioneer board (affected by the bug) and I 
had plan to make it a pure build farm, running VMs for Trisquel and gcc 
compile farm, etc. I even had it in my shopping cart, waiting for the 
foreign exchange rate to drop so I could buy it. Now, I don't think it 
is suitable for hosting anymore. I know Simon has one Pioneer board; 
WDYT? Can someone else convince me "the bug is not that serious"?

I do have a Lichee Pi 4A (affected by this bug). Can I help with 
Trisquel's riscv64 port? I can help build packages using sbuild, but 
IIUC we need to bootstrap from a foreign distro first (Ubuntu) to get a 
working schroot. Maybe I can help with that?

---
Anyways, since Simon asked about blobs on the gcc compile farm mailing 
list, if I recommend some boards, I would recommend the mature and 
reliable VisionFive 2 or the Pine Star64, both based on the same CPU 
Starfive JH7110 which is not vulnerable to this bug. They are not really 
as fast as T-Head C910, but they are inexpensive. You can buy like 5 of 
them for a cluster. VisionFive 2 is already supported by mainline linux 
(since 6.?), Star64 has support since 6.11-rc1, and the device tree can 
be easily backported to 6.8 or 6.9. As for u-boot, AFAIK, u-boot itself 
doesn't ship any blob. I have both of these boards, but I haven't 
test/install them yet.

-- 
Jing Luo
About me: https://jing.rocks/about/
GPG Fingerprint: 4E09 8D19 00AA 3F72 1899 2614 09B3 316E 13A1 1EFC
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