linux-kernel - Re: [PATCH] x86/bugs: Restructure ITS mitigation

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Message-ID: <20250515220243.fk4z7rifcxdm2e7h@desk>
Date: Thu, 15 May 2025 15:02:43 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: "Kaplan, David" <David.Kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/bugs: Restructure ITS mitigation

On Thu, May 15, 2025 at 09:15:59PM +0000, Kaplan, David wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
> 
> > -----Original Message-----
> > From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> > Sent: Thursday, May 15, 2025 4:12 PM
> > To: Kaplan, David <David.Kaplan@....com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>; Borislav Petkov <bp@...en8.de>; Peter
> > Zijlstra <peterz@...radead.org>; Josh Poimboeuf <jpoimboe@...nel.org>; Ingo
> > Molnar <mingo@...hat.com>; Dave Hansen <dave.hansen@...ux.intel.com>;
> > x86@...nel.org; H. Peter Anvin <hpa@...or.com>; linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH] x86/bugs: Restructure ITS mitigation
> >
> > Caution: This message originated from an External Source. Use proper caution
> > when opening attachments, clicking links, or responding.
> >
> >
> > On Thu, May 15, 2025 at 08:47:56AM -0500, David Kaplan wrote:
> > ...
> > > +static void __init its_apply_mitigation(void) {
> > > +     /* its=stuff forces retbleed stuffing and is enabled there. */
> > > +     if (its_mitigation != ITS_MITIGATION_ALIGNED_THUNKS)
> > > +             return;
> > > +
> > > +     if (!boot_cpu_has(X86_FEATURE_RETPOLINE))
> > > +             setup_force_cpu_cap(X86_FEATURE_INDIRECT_THUNK_ITS);
> > > +
> > > +     setup_force_cpu_cap(X86_FEATURE_RETHUNK);
> > > +     set_return_thunk(its_return_thunk);
> > > +}
> > > +
> > >  #undef pr_fmt
> > >  #define pr_fmt(fmt)     "Spectre V2 : " fmt
> > >
> > >
> > > base-commit: 04bdd560124ec4d02d1d11ee3abc88d51954d7b8
> >
> > I am having trouble applying this patch to upstream and tip/master. I can't seem to
> > find this base-commit in Linus's or tip tree. Please let me know what am I missing?
> 
> Hmm.  I was working off origin/master on tip.  This was the base commit in my git log from this morning:
> 
> commit 04bdd560124ec4d02d1d11ee3abc88d51954d7b8 (origin/master, origin/HEAD)
> Merge: 61e94712bb24 e59236b5a09e
> Author: Ingo Molnar <mingo@...nel.org>
> Date:   Thu May 15 10:16:23 2025 +0200
> 
> Not sure if something happened to it since?

Likely yes. I am getting:

	Notice: this object is not reachable from any branch.

when I go to this link:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit?id=04bdd560124ec4d02d1d11ee3abc88d51954d7b8

> Or is there something else I can provide to help?

No, I am able to apply now. Earlier my b4 based script failed because it
couldn't find the base-commit. It works when I am apply manually, sorry to
bother you.