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Date: Wed, 22 May 2024 17:34:33 +0200
From: Borislav Petkov <bp@alien8.de>
To: "Balasubrmanian, Vignesh" <vigbalas@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	"Balasubrmanian, Vignesh" <Vignesh.Balasubrmanian@amd.com>,
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Subject: Re: [PATCH v2 1/1] x86/elf: Add a new .note section containing
 Xfeatures information to x86 core files
Message-ID: <20240522153433.GCZk4QiX4Hf0OuI48E@fat_crate.local>
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 <4a090901-9705-40aa-ac3d-d67c52660f22@amd.com>
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On Wed, May 22, 2024 at 06:42:55PM +0530, Balasubrmanian, Vignesh wrote:
> > > +enum custom_feature {
> > > +     FEATURE_XSAVE_FP =3D 0,
> > > +     FEATURE_XSAVE_SSE =3D 1,
> > > +     FEATURE_XSAVE_YMM =3D 2,
> > > +     FEATURE_XSAVE_BNDREGS =3D 3,
> > > +     FEATURE_XSAVE_BNDCSR =3D 4,
> > > +     FEATURE_XSAVE_OPMASK =3D 5,
> > > +     FEATURE_XSAVE_ZMM_Hi256 =3D 6,
> > > +     FEATURE_XSAVE_Hi16_ZMM =3D 7,
> > > +     FEATURE_XSAVE_PT =3D 8,
> > > +     FEATURE_XSAVE_PKRU =3D 9,
> > > +     FEATURE_XSAVE_PASID =3D 10,
> > > +     FEATURE_XSAVE_CET_USER =3D 11,
> > > +     FEATURE_XSAVE_CET_SHADOW_STACK =3D 12,
> > > +     FEATURE_XSAVE_HDC =3D 13,
> > > +     FEATURE_XSAVE_UINTR =3D 14,
> > > +     FEATURE_XSAVE_LBR =3D 15,
> > > +     FEATURE_XSAVE_HWP =3D 16,
> > > +     FEATURE_XSAVE_XTILE_CFG =3D 17,
> > > +     FEATURE_XSAVE_XTILE_DATA =3D 18,
> > > +     FEATURE_MAX,
> > > +     FEATURE_XSAVE_EXTENDED_START =3D FEATURE_XSAVE_YMM,
> > > +     FEATURE_XSAVE_EXTENDED_END =3D FEATURE_XSAVE_XTILE_DATA,
> > > +};
> > Why can't this use the existing 'enum xfeature' which is providing
> > exactly the same information already?
> First version of patch was similar to what you mentioned here and other
> review comments to use existing kernel definitions.
> https://lore.kernel.org/linux-mm/20240314112359.50713-1-vigbalas@amd.co=
m/T/
>=20
> As per the review comment https://lore.kernel.org/linux-mm/202403141629=
54.GAZfMmAnYQoRjRbRzc@fat_crate.local/
> , modified the patch to be a independent of kernel internal definitions=
.
> Though this enum and below function=C2=A0 "get_sub_leaf" are not useful=
 now,=C2=A0 it
> will be required when we extend for a new/different features.

No, Thomas' sugggestion is to use the existing xfeature enum - not
define the same thing again.

Why do you need that enum custom_feature thing if you can use

/*
 * List of XSAVE features Linux knows about:
 */
enum xfeature {

from arch/x86/include/asm/fpu/types.h

?

--=20
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette