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Message-ID: <4a090901-9705-40aa-ac3d-d67c52660f22@amd.com>
Date: Wed, 22 May 2024 18:42:55 +0530
From: "Balasubrmanian, Vignesh" <vigbalas@....com>
To: Thomas Gleixner <tglx@...utronix.de>,
"Balasubrmanian, Vignesh" <Vignesh.Balasubrmanian@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-toolchains@...r.kernel.org" <linux-toolchains@...r.kernel.org>
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"christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
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Subject: Re: [PATCH v2 1/1] x86/elf: Add a new .note section containing
Xfeatures information to x86 core files
On 5/8/2024 6:32 PM, Thomas Gleixner wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> On Tue, May 07 2024 at 15:23, Vignesh Balasubramanian wrote:
>> +struct xfeat_component {
>> + u32 xfeat_type;
>> + u32 xfeat_sz;
>> + u32 xfeat_off;
>> + u32 xfeat_flags;
>> +} __packed;
> Why repeating xfeat_ for all member names?
>
> u32 type;
> u32 size;
> u32 offset;
> u32 flags;
>
> is sufficient and obvious, no?
>
>> +enum custom_feature {
>> + FEATURE_XSAVE_FP = 0,
>> + FEATURE_XSAVE_SSE = 1,
>> + FEATURE_XSAVE_YMM = 2,
>> + FEATURE_XSAVE_BNDREGS = 3,
>> + FEATURE_XSAVE_BNDCSR = 4,
>> + FEATURE_XSAVE_OPMASK = 5,
>> + FEATURE_XSAVE_ZMM_Hi256 = 6,
>> + FEATURE_XSAVE_Hi16_ZMM = 7,
>> + FEATURE_XSAVE_PT = 8,
>> + FEATURE_XSAVE_PKRU = 9,
>> + FEATURE_XSAVE_PASID = 10,
>> + FEATURE_XSAVE_CET_USER = 11,
>> + FEATURE_XSAVE_CET_SHADOW_STACK = 12,
>> + FEATURE_XSAVE_HDC = 13,
>> + FEATURE_XSAVE_UINTR = 14,
>> + FEATURE_XSAVE_LBR = 15,
>> + FEATURE_XSAVE_HWP = 16,
>> + FEATURE_XSAVE_XTILE_CFG = 17,
>> + FEATURE_XSAVE_XTILE_DATA = 18,
>> + FEATURE_MAX,
>> + FEATURE_XSAVE_EXTENDED_START = FEATURE_XSAVE_YMM,
>> + FEATURE_XSAVE_EXTENDED_END = 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.com/T/
As per the review comment
https://lore.kernel.org/linux-mm/20240314162954.GAZfMmAnYQoRjRbRzc@fat_crate.local/
, modified the patch to be a independent of kernel internal definitions.
Though this enum and below function "get_sub_leaf" are not useful now,
it will be required when we extend for a new/different features.
Please let us know your suggestions.
I will fix all other review comments in my next version.
>> +#ifdef CONFIG_COREDUMP
>> +static int get_sub_leaf(int custom_xfeat)
>> +{
>> + switch (custom_xfeat) {
>> + case FEATURE_XSAVE_YMM: return XFEATURE_YMM;
>> + case FEATURE_XSAVE_BNDREGS: return XFEATURE_BNDREGS;
>> + case FEATURE_XSAVE_BNDCSR: return XFEATURE_BNDCSR;
>> + case FEATURE_XSAVE_OPMASK: return XFEATURE_OPMASK;
>> + case FEATURE_XSAVE_ZMM_Hi256: return XFEATURE_ZMM_Hi256;
>> + case FEATURE_XSAVE_Hi16_ZMM: return XFEATURE_Hi16_ZMM;
>> + case FEATURE_XSAVE_PT: return XFEATURE_PT_UNIMPLEMENTED_SO_FAR;
>> + case FEATURE_XSAVE_PKRU: return XFEATURE_PKRU;
>> + case FEATURE_XSAVE_PASID: return XFEATURE_PASID;
>> + case FEATURE_XSAVE_CET_USER: return XFEATURE_CET_USER;
>> + case FEATURE_XSAVE_CET_SHADOW_STACK: return XFEATURE_CET_KERNEL_UNUSED;
>> + case FEATURE_XSAVE_HDC: return XFEATURE_RSRVD_COMP_13;
>> + case FEATURE_XSAVE_UINTR: return XFEATURE_RSRVD_COMP_14;
>> + case FEATURE_XSAVE_LBR: return XFEATURE_LBR;
>> + case FEATURE_XSAVE_HWP: return XFEATURE_RSRVD_COMP_16;
>> + case FEATURE_XSAVE_XTILE_CFG: return XFEATURE_XTILE_CFG;
>> + case FEATURE_XSAVE_XTILE_DATA: return XFEATURE_XTILE_DATA;
>> + default:
>> + pr_warn_ratelimited("Not a valid XSAVE Feature.");
>> + return 0;
>> + }
>> +}
> This function then maps the identical enums one to one. The only actual
> "functionality" is the default case and that's completely pointless.
thanks,
vigneshbalu.
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