linux-kernel - Re: [PATCH v4 04/19] x86/cea: Export per CPU array 'cea_exception

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Message-ID: <Z_eHGjzR33LMqLfL@infradead.org>
Date: Thu, 10 Apr 2025 01:53:46 -0700
From: Christoph Hellwig <hch@...radead.org>
To: "Xin Li (Intel)" <xin@...or.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, kvm@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
	andrew.cooper3@...rix.com, luto@...nel.org, peterz@...radead.org,
	chao.gao@...el.com, xin3.li@...el.com
Subject: Re: [PATCH v4 04/19] x86/cea: Export per CPU array
 'cea_exception_stacks' for KVM to use

On Fri, Mar 28, 2025 at 10:11:50AM -0700, Xin Li (Intel) wrote:
> The per CPU array 'cea_exception_stacks' points to per CPU stacks
> +/*
> + * FRED introduced new fields in the host-state area of the VMCS for
> + * stack levels 1->3 (HOST_IA32_FRED_RSP[123]), each respectively
> + * corresponding to per CPU stacks for #DB, NMI and #DF.  KVM must
> + * populate these each time a vCPU is loaded onto a CPU.
> + */
> +EXPORT_PER_CPU_SYMBOL(cea_exception_stacks);

Exporting data vs accessors for it is usually a bad idea.  Doing a
non-_GPl for such a very low level data struture is even worse.