linux-kernel - Re: [STABLE REGRESSION] Possible missing backport of x86_match

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Message-ID: <20240925195102.GA17227@ranerica-svr.sc.intel.com>
Date: Wed, 25 Sep 2024 12:51:02 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: "Zhang, Rui" <rui.zhang@...el.com>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"regressions@...mhuis.info" <regressions@...mhuis.info>,
	"Neri, Ricardo" <ricardo.neri@...el.com>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"bp@...en8.de" <bp@...en8.de>,
	"Gupta, Pawan Kumar" <pawan.kumar.gupta@...el.com>,
	"regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"thomas.lindroth@...il.com" <thomas.lindroth@...il.com>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [STABLE REGRESSION] Possible missing backport of x86_match_cpu()
 change in v6.1.96

On Wed, Sep 25, 2024 at 05:20:41AM +0000, Zhang, Rui wrote:
> > > 
> > > If so, can you submit the needed backports for us to apply?  That's
> > > the
> > > easiest way for us to take them, thanks.
> > 
> > I audited all the uses of x86_match_cpu(match). All callers that
> > construct
> > the `match` argument using the family of X86_MATCH_* macros from
> > arch/x86/
> > include/asm/cpu_device_id.h function correctly because the commit B
> > has
> > been backported to v6.1.99 and to v6.6.50 -- 93022482b294 ("x86/cpu:
> > Fix
> > x86_match_cpu() to match just X86_VENDOR_INTEL").
> > 
> > Only those callers that use their own thing to compose the `match`
> > argument
> > are buggy:
> >     * arch/x86/mm/init.c
> >     * drivers/powercap/intel_rapl_msr.c (only in 6.1.99)
> 
> Thanks for auditing this. I overlooked the intel_rapl driver case.
> > 
> > Summarizing, v6.1.99 needs these two commits from mainline
> >     * d05b5e0baf42 ("powercap: RAPL: fix invalid initialization for
> >       pl4_supported field")
> >     * 2eda374e883a ("x86/mm: Switch to new Intel CPU model defines")
> > 
> > v6.6.50 only needs the second commit.
> 
> Well, commit B 93022482b294 ("x86/cpu: Fix x86_match_cpu() to match
> just X86_VENDOR_INTEL") is backported to all stable kernels. And the
> above two broken cases are also there.
> 
> So I suppose we need to backport all of them to 5.x stable kernel as
> well.

Indeed, this the case. It has been backported to v5.15.y and v5.10.y, but
not to v5.4.y nor 4.19.y.

I found one more case in those two v5.x versions. I will post the
backports.