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From:   "Li, Xin3" <xin3.li@intel.com>
To:     Peter Zijlstra <peterz@infradead.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
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        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "hpa@zytor.com" <hpa@zytor.com>
Subject: RE: [PATCH 6/6] x86/gsseg: use the LKGS instruction if available for
 load_gs_index()
Thread-Topic: [PATCH 6/6] x86/gsseg: use the LKGS instruction if available for
 load_gs_index()
Thread-Index: AQHY2Z1YsyE3enznIkOfLcepaehVE64DBB+AgAA15gA=
Date:   Fri, 7 Oct 2022 18:01:06 +0000
Message-ID: <BN6PR1101MB21611798953AADA4DFD71719A85F9@BN6PR1101MB2161.namprd11.prod.outlook.com>
References: <20221006154041.13001-1-xin3.li@intel.com>
 <20221006154041.13001-7-xin3.li@intel.com>
 <Y0A77RLAgXQyrVPq@hirez.programming.kicks-ass.net>
In-Reply-To: <Y0A77RLAgXQyrVPq@hirez.programming.kicks-ass.net>
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> > +	alternative_io("1: call asm_load_gs_index\n"
> > +		       ".pushsection \".fixup\",\"ax\"\n"
> > +		       "2:	xorl %k[sel], %k[sel]\n"
> > +		       "	jmp 1b\n"
> > +		       ".popsection\n"
> > +		       _ASM_EXTABLE(1b, 2b),
> > +		       _ASM_BYTES(0x3e) LKGS_DI,
> > +		       X86_FEATURE_LKGS,
> > +		       ASM_OUTPUT2([sel] "+D" (sel), ASM_CALL_CONSTRAINT),
> > +		       ASM_NO_INPUT_CLOBBER(_ASM_AX));
> >  }
>=20
> I'm very sure none of this was tested... the .fixup section hasn't existe=
d for
> almost a year now.

Weird, did you ever check a kernel dump?

>=20
>   e5eefda5aa51 ("x86: Remove .fixup section")