linux-kernel - Re: [PATCH v5 16/16] Revert "x86/lam: Disable ADDRESS

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Message-ID: <87sesfubuh.fsf@ubik.fi.intel.com>
Date: Tue, 29 Oct 2024 00:00:38 +0200
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: "Kirill A. Shutemov" <kirill@...temov.name>
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Subject: Re: [PATCH v5 16/16] Revert "x86/lam: Disable ADDRESS_MASKING in
 most cases"

"Kirill A. Shutemov" <kirill@...temov.name> writes:

> 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@...ux.intel.com>
>> CC: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
>
> 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").

Forgot about that one. Thanks!

Regards,
--
Alex