linux-kernel - Re: [PATCH v3 09/10] x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL

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Message-ID: <7bee70fd-b2b9-4466-a694-4bf3486b19c7@intel.com>
Date: Sun, 9 Mar 2025 22:20:47 -0700
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: Chao Gao <chao.gao@...el.com>
CC: <tglx@...utronix.de>, <dave.hansen@...el.com>, <x86@...nel.org>,
	<seanjc@...gle.com>, <pbonzini@...hat.com>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>, <peterz@...radead.org>, <rick.p.edgecombe@...el.com>,
	<weijiang.yang@...el.com>, <john.allen@....com>, <bp@...en8.de>
Subject: Re: [PATCH v3 09/10] x86/fpu/xstate: Introduce
 XFEATURE_MASK_KERNEL_DYNAMIC xfeature set

On 3/9/2025 8:49 PM, Chao Gao wrote:
> 
> It was suggested by Sean [1].
...
 > [1]: https://lore.kernel.org/kvm/ZTf5wPKXuHBQk0AN@google.com/

But, you're defining a kernel "dynamic" feature while introducing a
"guest-only" xfeature concept. Both seem to be mixed together with this
patch. Why not call it as a guest-only feature? That's what Sean was
suggesting, no?

"I would much prefer to avoid the whole "dynamic" thing and instead make 
CET explicitly guest-only.  E.g. fpu_kernel_guest_only_xfeatures?  Or 
even better if it doesn't cause weirdness elsewhere, a dedicated 
fpu_guest_cfg.  For me at least, a fpu_guest_cfg would make it easier to 
understand what all is going on."

Thanks,
Chang