From: Borislav Petkov <bp@alien8.de>
To: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Breno Leitao <leitao@debian.org>,
tglx@linutronix.de, mingo@redhat.com,
dave.hansen@linux.intel.com, hpa@zytor.com, jpoimboe@kernel.org,
peterz@infradead.org, x86@kernel.org, cascardo@canonical.com,
leit@meta.com, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] x86/bugs: Explicitly clear speculative MSR bits
Date: Thu, 12 Jan 2023 11:34:08 +0100 [thread overview]
Message-ID: <Y7/iIKl/F8MOrVdD@zn.tnic> (raw)
In-Reply-To: <20230112070037.q6cg23tn57onmxfi@desk>
On Wed, Jan 11, 2023 at 11:00:37PM -0800, Pawan Gupta wrote:
> > SPEC_CTRL_RRSBA_DIS_S is a disable bit and I presume it needs to stay enabled.
>
> The mitigation is enabled when this bit is set. When set, it prevents RET
> target to be predicted from alternate predictors (BTB). This should stay
> 0, unless enabled by a mitigation mode.
>
> > Only when spec_ctrl_disable_kernel_rrsba() runs. And I'd say perf-wise it
> > doesn't cost that much...
>
> I guess this doesn't matter now, because this patch is resetting it by
> default that keeps the mitigation disabled with no perf impact.
Ok, lemme queue it then.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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prev parent reply other threads:[~2023-01-12 10:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-28 15:31 [PATCH v3] x86/bugs: Explicitly clear speculative MSR bits Breno Leitao
2023-01-11 12:51 ` Borislav Petkov
2023-01-12 7:00 ` Pawan Gupta
2023-01-12 10:34 ` Borislav Petkov [this message]
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