Received-SPF: pass (google.com: domain of linux-kernel+bounces-60194-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Date: Fri, 9 Feb 2024 16:40:22 -0800
From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Daniel Sneddon <daniel.sneddon@linux.intel.com>,
	antonio.gomez.iglesias@linux.intel.com,
	alyssa.milburn@linux.intel.com, andrew.cooper3@citrix.com,
	linux-kernel@vger.kernel.org,
	Alyssa Milburn <alyssa.milburn@intel.com>
Subject: Re: [PATCH] x86/bugs: Default retbleed to =stuff when retpoline is
 auto enabled
Message-ID: <20240210004022.aff2dnr6dzwq5gkq@treble>
References: <20240208-retbleed-auto-stuff-v1-1-6f12e513868f@linux.intel.com>
 <20240209185625.hca6lts6dv4cd3fu@treble>
 <20240209203346.gwbfyx3huiaozg4s@desk>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20240209203346.gwbfyx3huiaozg4s@desk>

On Fri, Feb 09, 2024 at 12:33:46PM -0800, Pawan Gupta wrote:
> On Fri, Feb 09, 2024 at 10:56:25AM -0800, Josh Poimboeuf wrote:
> > On Thu, Feb 08, 2024 at 05:12:15PM -0800, Pawan Gupta wrote:
> > > +			   spectre_v2_enabled == SPECTRE_V2_RETPOLINE) {
> > > +			if (IS_ENABLED(CONFIG_CALL_DEPTH_TRACKING))
> > > +				retbleed_mitigation = RETBLEED_MITIGATION_STUFF;
> > > +			else
> > > +				pr_err("WARNING: Retpoline enabled, but kernel not compiled with CALL_DEPTH_TRACKING.\n");
> > 
> > If retbleed is vulnerable then the sysfs file should show that.
> 
> It does shows vulnerable, retbleed_mitigation is not set to
> RETBLEED_MITIGATION_STUFF for CONFIG_CALL_DEPTH_TRACKING=n.

Ah right, in that case retbleed_mitigation still has its initialized
value of RETBLEED_MITIGATION_NONE.

> > Also, I think this pr_err() is redundant with RETBLEED_INTEL_MSG and can
> > be removed.
> 
> IMO, they both serve a different purpose, RETBLEED_INTEL_MSG is a
> generic warning, and the message with !CONFIG_CALL_DEPTH_TRACKING hints
> a corrective action.
> 
> If you look at "case RETBLEED_CMD_STUFF" it also prints a separate warning for
> !CONFIG_CALL_DEPTH_TRACKING:

Yep, makes sense.

-- 
Josh