From: Borislav Petkov <bp@suse.de>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH] taa fix
Date: Thu, 7 Nov 2019 10:25:33 +0100 [thread overview]
Message-ID: <20191107092533.GA4243@zn.tnic> (raw)
In-Reply-To: <20191107022646.6h724wh4im5zxvw2@treble>
On Wed, Nov 06, 2019 at 08:26:46PM -0600, speck for Josh Poimboeuf wrote:
> From: Josh Poimboeuf <jpoimboe@redhat.com>
> Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
Subject should be something like "Print TAA_MSG_SMT on IBRS_ALL CPUs
too" or so.
> For new IBRS_ALL CPUs, the Enhanced IBRS check at the beginning of
> cpu_bugs_smt_update() causes the function to return early,
> unintentionally skipping the MDS and TAA logic.
>
> I don't think it's a problem for MDS, because AFAICT there appears to be
> no overlap between IBRS_ALL and MDS-affected CPUs. So the MDS
> mitigation would be disabled and nothing would need to be done in this
> function anyway.
>
> But for TAA, the TAA_MSG_SMT string will never get printed on Cascade
> Lake and newer.
>
> The check is superfluous anyway: when 'spectre_v2_enabled' is
> SPECTRE_V2_IBRS_ENHANCED, 'spectre_v2_user' is always
> SPECTRE_V2_USER_NONE, and so the 'spectre_v2_user' switch statement
> handles it appropriately by doing nothing. So just remove the check.
>
> Fixes: 1b42f017415b ("x86/speculation/taa: Add mitigation for TSX Async Abort")
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
> arch/x86/kernel/cpu/bugs.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 850005590167..4c7b0fa15a19 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -886,10 +886,6 @@ static void update_mds_branch_idle(void)
>
> void cpu_bugs_smt_update(void)
> {
> - /* Enhanced IBRS implies STIBP. No update required. */
> - if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
> - return;
> -
> mutex_lock(&spec_ctrl_mutex);
>
> switch (spectre_v2_user) {
> --
With that addressed:
Reviewed-by: Borislav Petkov <bp@suse.de>
--
Regards/Gruss,
Boris.
SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg
--
next prev parent reply other threads:[~2019-11-07 9:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 2:26 [MODERATED] [PATCH] taa fix Josh Poimboeuf
2019-11-07 2:41 ` [MODERATED] " Tyler Hicks
2019-11-07 9:25 ` Borislav Petkov [this message]
2019-11-07 13:47 ` Josh Poimboeuf
2019-11-07 13:49 ` Borislav Petkov
2019-11-07 14:59 ` Josh Poimboeuf
2019-11-07 15:04 ` Thomas Gleixner
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