linux-kernel - Re: [PATCH v2 1/2] hyperv: add definitions for arm64 gpa intercepts

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Message-ID: <993970797.13531.1767629162352@app.mailbox.org>
Date: Mon, 5 Jan 2026 08:06:02 -0800 (PST)
From: vdso@...lbox.org
To: Anirudh Rayabharam <anirudh@...rudhrb.com>
Cc: "kys@...rosoft.com" <kys@...rosoft.com>,
	"haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
	"wei.liu@...nel.org" <wei.liu@...nel.org>,
	"decui@...rosoft.com" <decui@...rosoft.com>,
	"longli@...rosoft.com" <longli@...rosoft.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] hyperv: add definitions for arm64 gpa intercepts

> On 01/05/2026 4:28 AM  Anirudh Rayabharam <anirudh@...rudhrb.com> wrote:
> 

[...]

>  
> +#if IS_ENABLED(CONFIG_ARM64)
> +union hv_arm64_vp_execution_state {
> +	u16 as_uint16;
> +	struct {
> +		u16 cpl:2; /* Exception Level (EL) */

Anirudh,

Appreciate following up on the CPL field in that ARM64 structure
and adding the comment!

Still, using something from the x86 parlance (CPL) and adding a comment
stating that this is actually ARM64 EL certainly needs an explanation
as to _why_ using an x86 term here is beneficial, why not just call
the field "el"? As an analogy, here is a thought experiment of writing

#ffdef CONFIG_ARM64
u64 rax; /* This is X0 */
#endif

where an x86 register name would be used to refer to X0 on ARM64, and
that doen't look natural.

So far, I can't seem to find drawbacks in naming this field "el", only
benefits:
* ARM64 folks will immediately know what this field is, and
* the comment isn't required to explain the situation to the reader.

Do you foresee any drawbacks of calling the field "el" and dropping
the comment? If you do, would these drawbacks outweigh the benefits?

[...]

--
Cheers,
Roman