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From: "Ahmed S. Darwish" <darwi@linutronix.de>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org,
	Konstantin Belousov <kib@kib.kiev.ua>,
	John Baldwin <jhb@freebsd.org>
Subject: Re: [RFC PATCH] x86/bhyve: Detect FreeBSD Bhyve hypervisor
Date: Thu, 14 Aug 2025 18:51:28 +0200	[thread overview]
Message-ID: <aJ4UEO3gRUiuD-4F@lx-t490> (raw)
In-Reply-To: <8ff6b4cad51167c6226304483544a6828d3f7e0c.camel@infradead.org>

On Thu, 14 Aug 2025, David Woodhouse wrote:
> On Thu, 2025-08-14 at 12:15 +0200, Borislav Petkov wrote:
>
> >
> > Which makes it, what, 0x4000_0001?
> >
> > I presume there's an agreement among all the hypervisors...?
>
> There is no such agreement about CPUID; by *coincidence* most of them
> seem to use 0x4000_0?01 as their feature leaf, but the feature bits in
> each such leaf are completely different and the guest doesn't look at a
> given leaf unless it knows that specific hypervisor. Which is why the
> 15-bit enlightenment is advertised differently by each hypervisor
> despite being precisely the same enlightenment across them all.
>

For what it takes, such hypervisor leaves, in the 0x40000000 range, will
be converted by the ongoing x86-cpuid-db CPUID parser work at some point.

(Another iteration of the CPUID parser is to be posted today.)

Thanks,
Ahmed

      reply	other threads:[~2025-08-14 16:51 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-11 11:16 [RFC PATCH] x86/bhyve: Detect FreeBSD Bhyve hypervisor David Woodhouse
2025-08-13 21:07 ` David Woodhouse
2025-08-14 10:15 ` Borislav Petkov
2025-08-14 11:13   ` David Woodhouse
2025-08-14 16:51     ` Ahmed S. Darwish [this message]

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