linux-kernel - Re: [RFC PATCH] x86/bhyve: Detect FreeBSD Bhyve hypervisor

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Message-ID: <20250814101552.GAaJ23WBZ-O3Yuu64t@fat_crate.local>
Date: Thu, 14 Aug 2025 12:15:52 +0200
From: Borislav Petkov <bp@...en8.de>
To: David Woodhouse <dwmw2@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	David Woodhouse <dwmw@...zon.co.uk>,
	"Ahmed S. Darwish" <darwi@...utronix.de>,
	linux-kernel@...r.kernel.org, Konstantin Belousov <kib@....kiev.ua>,
	John Baldwin <jhb@...ebsd.org>
Subject: Re: [RFC PATCH] x86/bhyve: Detect FreeBSD Bhyve hypervisor

On Mon, Aug 11, 2025 at 01:16:42PM +0200, David Woodhouse wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> This detects the Bhyve hypervisor

Users of this are?

Wikipedia says it already supports Linux :-P

> and enables 15-bit MSI support if
> available.
> 
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> ---
> RFC because the CPUID_BHYVE_FEATURES leaf is submitted to FreeBSD in

Which makes it, what, 0x4000_0001?

I presume there's an agreement among all the hypervisors...?

> https://github.com/freebsd/freebsd-src/pull/1797 and not yet merged.
> And because I haven't tested this patch at all other than building it.
> 
> It's tiny so I didn't put it behind a separate CONFIG_BHYVE_GUEST.
> Should I?

Yeah, please do.

> +/* Features advertised in CPUID_BHYVE_FEATURES %eax */
> +#define CPUID_BHYVE_FEAT_EXT_DEST_ID	(1UL << 0) /* MSI Extended Dest ID */
> +
> +static uint32_t __init bhyve_detect(void)
> +{
> +	if (boot_cpu_data.cpuid_level < 0 ||
> +            !boot_cpu_has(X86_FEATURE_HYPERVISOR))

cpu_feature_enabled()

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette