Re: [PATCH v5 16/16] Revert "x86/lam: Disable ADDRESS_MASKING in most cases"

[Kirill A. Shutemov]

On Mon, Oct 28, 2024 at 06:08:04PM +0200, Alexander Shishkin wrote:
> This reverts commit 3267cb6d3a174ff83d6287dcd5b0047bbd912452.
> 
> LASS mitigates the Spectre based on LAM (SLAM) [1] and an earlier
> commit made LAM depend on LASS, so we no longer need to disable LAM at
> compile time, so revert the commit that disables LAM.
> 
> [1] https://download.vusec.net/papers/slam_sp24.pdf
> 
> Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> CC: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>

Before re-enabling LAM, you need to uncomment X86_FEATURE_LAM check in
arch/x86/kernel/cpu/common.c introduced in recent 86e6b1547b3d ("x86: fix
user address masking non-canonical speculation issue").

-- 
  Kiryl Shutsemau / Kirill A. Shutemov