linux-kernel - [PATCH 0/3] x86/alternative: Make alternative patching more robust

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Message-ID: <20250929112947.27267-1-jgross@suse.com>
Date: Mon, 29 Sep 2025 13:29:44 +0200
From: Juergen Gross <jgross@...e.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Juergen Gross <jgross@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 0/3] x86/alternative: Make alternative patching more robust

This small series makes alternative patching a little bit more robust
for ALTERNATIVE_<n>() use cases by using a local buffer for merging
multiple patch actions of the same location.

With this series applied intermediate patch results due to multiple
features matching in a ALTERNATIVE_<n>() invocation won't be visible
to e.g. interrupt handlers being invoked between the single patching
operations.

Additionally any indirect call replacements with their direct call
equivalents no longer need to be placed carefully to be the first
executed patch action of an ALTERNATIVE_<n>() invocation, as the
needed reference of the indirect call of the original instruction
will still see the original code.

These patches have been sent before as part of my MSR paravirt rework
series. I'm sending them now as an independent series, as V2 of the
MSR series is no longer relying on them.

Juergen Gross (3):
  x86/alternative: Drop not needed test after call of alt_replace_call()
  x86/alternative: Refactor apply_alternatives()
  x86/alternative: Patch a single alternative location only once

 arch/x86/kernel/alternative.c | 86 ++++++++++++++++++++---------------
 1 file changed, 49 insertions(+), 37 deletions(-)

-- 
2.51.0