Bug#1017425: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it

To: Ben Hutchings <ben@decadent.org.uk>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, 1017425@bugs.debian.org, Martin-Éric Racine <martin-eric.racine@iki.fi>, stable@vger.kernel.org, regressions@lists.linux.dev, Daniel Sneddon <daniel.sneddon@linux.intel.com>, Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Subject: Bug#1017425: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 19 Aug 2022 10:47:21 +0200
Message-id: <[🔎] Yv9OGVc+WpoDAB0X@worktop.programming.kicks-ass.net>
Reply-to: Peter Zijlstra <peterz@infradead.org>, 1017425@bugs.debian.org
In-reply-to: <Yv7aRJ/SvVhSdnSB@decadent.org.uk>
References: <Yv7aRJ/SvVhSdnSB@decadent.org.uk> <[🔎] 166062224255.2056.9595118849979455037.reportbug@pxeth.lan>

On Fri, Aug 19, 2022 at 02:33:08AM +0200, Ben Hutchings wrote:
> From: Ben Hutchings <benh@debian.org>
> 
> 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 ?!?

Reply to:

References:
- Bug#1017425: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it
  - From: Ben Hutchings <ben@decadent.org.uk>
- Bug#1017425: 5.10.0-17-686-pae: repeatedly crashes during initrd loading [PIII]
  - From: Martin-Éric Racine <martin-eric.racine@iki.fi>

Prev by Date: Processed: bug 1017425 is forwarded to https://lore.kernel.org/lkml/Yv7aRJ%2FSvVhSdnSB@decadent.org.uk/
Next by Date: Bug#1017425: 5.10.0-17-686-pae: repeatedly crashes during initrd loading [PIII]
Previous by thread: Bug#1017425: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it
Next by thread: Bug#1017425: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it
Index(es):
- Date
- Thread