Control: retitle -1 [i386] Unconditional LFENCE instructions in FILL_RETURN_BUFFER Control: tag -1 confirmed upstream Control: found -1 5.18.14-1
On Wed, 2022-08-17 at 11:42 +0200, Etienne Vogt wrote: > I can confirm that this bug also occurs on Athlon XP systems (Generic VIA > KT333 motherboard, CPU AMD Athlon(tm) XP 2600+) : kernel panic early on > boot. > > I suspect someone thought it would be a good idea to compile the kernel > for P4 only, as both PIII and Athlon XP processors lack the SSE2 > instruction set. > That was a good guess, though we don't change the configuration like that in stable updates. The RETbleed mitigations, which are not needed on these CPUs or even functional on 32-bit kernels, interact with the Spectre v2 mitigations, which *are* used on these CPUs. And unfortunately the RETbleed mitigations added some unconditional LFENCE instructions, which should be conditional since they are part of SSE2. As a temporary workaround, disabling the Spectre v2 mitigation with the kernel parameter "nospectre_v2" should allow this kernel version to run on older CPUs without SSE2. We'll fix this properly in a later update. Ben. -- Ben Hutchings I haven't lost my mind; it's backed up on tape somewhere.
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