Bug#1017425: 5.10.0-17-686-pae: repeatedly crashes during initrd loading [PIII]
On Thu, Aug 18, 2022 at 10:59 PM Ben Hutchings <ben@decadent.org.uk> wrote:
>
> 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.
That breakage affects Stable.
Expecting people to go and use workarounds on what was meant to be a
stable update isn't acceptable.
I really hope that the fix will be pushed within the next 24 hours
with high urgency.
Martin-Éric
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