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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <atnnav7x4gzbeghpuh4fjpdig3i4zxzb56kpfvx3stgelajbm6@52lzmsycwzss>
Date: Tue, 6 Jan 2026 00:57:07 +0530
From: Anirudh Rayabharam <anirudh@...rudhrb.com>
To: vdso@...lbox.org
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 Mon, Jan 05, 2026 at 08:06:02AM -0800, vdso@...lbox.org wrote:
> 
> > 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!

My bad, actually I was gonna explain this in a reply to the previous
thread but it slipped my mind.

> 
> 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.

Well, in this case neither CPL nor EL is an architecturally defined
register name. These are just architectural concepts.

> 
> 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?

As a general rule we want to keep these headers exactly same as the
hypervisor headers so that we can directly ingest them at some point in
the future.

I am not seeing a substantial benefit in breaking that rule. The CPL ->
EL analogy is not a huge leap to make IMO and the comment helps. One
could think of "current privilege level" as a generic term here.

Thanks,
Anirudh.

> 
> [...]
> 
> --
> Cheers,
> Roman