Return to Level1Techs.com

Is the Via c7 immune to spectre?

Guys, are you sure the Via C7 is invulnerable to Spectre and Meltdown? It doesn’t seem like it:

$ cat /proc/cpuinfo | grep bugs
bugs            : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit

$ grep . /sys/devices/system/cpu/vulnerabilities/*
/sys/devices/system/cpu/vulnerabilities/itlb_multihit:KVM: Vulnerable
/sys/devices/system/cpu/vulnerabilities/l1tf:Mitigation: PTE Inversion
/sys/devices/system/cpu/vulnerabilities/mds:Vulnerable; SMT disabled
/sys/devices/system/cpu/vulnerabilities/meltdown:Vulnerable
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass:Vulnerable
/sys/devices/system/cpu/vulnerabilities/spectre_v1:Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers
/sys/devices/system/cpu/vulnerabilities/spectre_v2:Vulnerable, STIBP: disabled
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort:Not affected

Why in gods name do you have a C7

3 Likes

I moved your post to a new topic. In the future, please make a new topic if the thread has had no replies for over 9 months.

2 Likes

Seems like linux isn’t properly checking for cpu arch and setting generic x86 flags, especially since it’s applying meltdown which really should not be set for Via anything.

The way the kernel logic works, is to apply all mitigations on x86 anything and then use certain flags to opt out specific mitigations on some CPU’s

Basically nobody bothered to code the mitigation exceptions for C7.
I’ve you’ve got a 5.2+ kernel just boot with mitigations=off flag.

C3/C7 is in order execution based with basic prefetch, no speculative execution of any sort. Hence spectre, meltdown, especially MDS (LOL!!!) the whole lot are impossible on the hardware.

3 Likes

Because you didn’t know it was available, of course. :stuck_out_tongue:

3 Likes

Nice to know, thank you!