From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
antonio.gomez.iglesias@linux.intel.com,
Josh Poimboeuf <jpoimboe@kernel.org>
Subject: Re: [PATCH v2] x86/bugs: Warn when "ibrs" mitigation is selected on Enhanced IBRS parts
Date: Fri, 15 Jul 2022 10:21:13 -0700 [thread overview]
Message-ID: <20220715172113.74t65hgxi2o32wv6@desk> (raw)
In-Reply-To: <YtD6V5i0rS3szVIX@kroah.com>
On Fri, Jul 15, 2022 at 07:25:43AM +0200, Greg KH wrote:
> On Thu, Jul 14, 2022 at 04:15:35PM -0700, Pawan Gupta wrote:
> > IBRS mitigation for spectre_v2 forces write to MSR_IA32_SPEC_CTRL at
> > every kernel entry/exit. On Enhanced IBRS parts setting
> > MSR_IA32_SPEC_CTRL[IBRS] only once at boot is sufficient. MSR writes at
> > every kernel entry/exit incur unnecessary performance loss.
> >
> > When Enhanced IBRS feature is present, print a warning about this
> > unnecessary performance loss.
> >
> > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
> > ---
> > v1->v2: Instead of changing the mitigation, print a warning about the
> > perf loss.
> >
> > v1: https://lore.kernel.org/lkml/0456b35fb9ef957d9a9138e0913fb1a3fd445dff.1657747493.git.pawan.kumar.gupta@linux.intel.com/
> >
> > arch/x86/kernel/cpu/bugs.c | 3 +++
> > 1 file changed, 3 insertions(+)
>
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree. Please read:
> https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
>
> </formletter>
Sorry, I CCed stable@ by mistake. This version just adds a warning, it
is not intended to be backported.
Thanks,
Pawan
prev parent reply other threads:[~2022-07-15 17:21 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-14 5:32 [PATCH] x86/bugs: Switch to "auto" when "ibrs" selected on Enhanced IBRS parts Pawan Gupta
2022-07-14 11:17 ` Thadeu Lima de Souza Cascardo
2022-07-14 11:42 ` Peter Zijlstra
2022-07-14 14:59 ` Pawan Gupta
2022-07-14 16:01 ` Josh Poimboeuf
2022-07-14 17:03 ` Peter Zijlstra
2022-07-14 17:38 ` Josh Poimboeuf
2022-07-14 18:11 ` Peter Zijlstra
2022-07-14 18:42 ` Pawan Gupta
2022-07-14 23:15 ` [PATCH v2] x86/bugs: Warn when "ibrs" mitigation is " Pawan Gupta
2022-07-15 0:11 ` Thadeu Lima de Souza Cascardo
2022-07-15 2:00 ` Pawan Gupta
2022-07-15 5:25 ` Greg KH
2022-07-15 17:21 ` Pawan Gupta [this message]
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