Re: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it
flat view
From: Peter Zijlstra <peterz@infradead.org>
Date: 2022-08-19 08:47:52
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lkml, regressions
On Fri, Aug 19, 2022 at 02:33:08AM +0200, Ben Hutchings wrote:
From: Ben Hutchings <redacted> The mitigation for PBRSB includes adding LFENCE instructions to the RSB filling sequence. However, RSB filling is done on some older CPUs that don't support the LFENCE instruction.
Wait; what? There are chips that enable the RSB mitigations and DONT have LFENCE ?!?