On Thu, 2022-08-18 at 21:59 +0200, Ben Hutchings wrote:
> Control: retitle -1 [i386] Unconditional LFENCE instructions in 
> 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

I mean PBRSB, not RETbleed.  There are so many different issues to keep
track of...


> 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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