Commit fa1d1171 authored by David Woodhouse's avatar David Woodhouse Committed by Borislav Petkov (AMD)
Browse files

x86/cpu: Detect FreeBSD Bhyve hypervisor 

Detect the Bhyve hypervisor and enable 15-bit MSI support if available.

Detecting Bhyve used to be a purely cosmetic issue of the kernel printing
'Hypervisor detected: Bhyve' at boot time.

But FreeBSD 15.0 will support¹ the 15-bit MSI enlightenment to support
more than 255 vCPUs (http://david.woodhou.se/ExtDestId.pdf) which means
there's now actually some functional reason to do so.

  ¹ https://github.com/freebsd/freebsd-src/commit/313a68ea20b4



  [ bp: Massage, move tail comment ontop. ]

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Acked-by: default avatarAhmed S. Darwish <darwi@linutronix.de>
Link: https://lore.kernel.org/03802f6f7f5b5cf8c5e8adfe123c397ca8e21093.camel@infradead.org
parent f83ec76b

arch/x86/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -879,6 +879,15 @@ config ACRN_GUEST 
	  IOT with small footprint and real-time features. More details can be

	  found in https://projectacrn.org/.



config BHYVE_GUEST

	bool "Bhyve (BSD Hypervisor) Guest support"

	depends on X86_64

	help

	  This option allows to run Linux to recognise when it is running as a

	  guest in the Bhyve hypervisor, and to support more than 255 vCPUs when

	  when doing so. More details about Bhyve can be found at https://bhyve.org

	  and https://wiki.freebsd.org/bhyve/.



config INTEL_TDX_GUEST

	bool "Intel TDX (Trust Domain Extensions) - Guest Support"

	depends on X86_64 && CPU_SUP_INTEL

arch/x86/include/asm/hypervisor.h

+2 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ enum x86_hypervisor_type { 
	X86_HYPER_KVM,

	X86_HYPER_JAILHOUSE,

	X86_HYPER_ACRN,

	X86_HYPER_BHYVE,

};



#ifdef CONFIG_HYPERVISOR_GUEST
@@ -64,6 +65,7 @@ extern const struct hypervisor_x86 x86_hyper_xen_pv; 
extern const struct hypervisor_x86 x86_hyper_kvm;

extern const struct hypervisor_x86 x86_hyper_jailhouse;

extern const struct hypervisor_x86 x86_hyper_acrn;

extern const struct hypervisor_x86 x86_hyper_bhyve;

extern struct hypervisor_x86 x86_hyper_xen_hvm;



extern bool nopv;

arch/x86/kernel/cpu/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ obj-$(CONFIG_X86_SGX) += sgx/ 
obj-$(CONFIG_X86_LOCAL_APIC)		+= perfctr-watchdog.o



obj-$(CONFIG_HYPERVISOR_GUEST)		+= vmware.o hypervisor.o mshyperv.o

obj-$(CONFIG_BHYVE_GUEST)		+= bhyve.o

obj-$(CONFIG_ACRN_GUEST)		+= acrn.o



obj-$(CONFIG_DEBUG_FS)			+= debugfs.o

arch/x86/kernel/cpu/bhyve.c

0 → 100644
+66 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * FreeBSD Bhyve guest enlightenments

 *

 * Copyright © 2025 Amazon.com, Inc. or its affiliates.

 *

 * Author: David Woodhouse <dwmw2@infradead.org>

 */



#include <linux/init.h>

#include <linux/export.h>

#include <asm/processor.h>

#include <asm/hypervisor.h>



static uint32_t bhyve_cpuid_base;

static uint32_t bhyve_cpuid_max;



#define BHYVE_SIGNATURE			"bhyve bhyve "



#define CPUID_BHYVE_FEATURES		0x40000001



/* Features advertised in CPUID_BHYVE_FEATURES %eax */



/* MSI Extended Dest ID */

#define CPUID_BHYVE_FEAT_EXT_DEST_ID	(1UL << 0)



static uint32_t __init bhyve_detect(void)

{

	if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))

                return 0;



	bhyve_cpuid_base = cpuid_base_hypervisor(BHYVE_SIGNATURE, 0);

	if (!bhyve_cpuid_base)

		return 0;



	bhyve_cpuid_max = cpuid_eax(bhyve_cpuid_base);

	return bhyve_cpuid_max;

}



static uint32_t bhyve_features(void)

{

	unsigned int cpuid_leaf = bhyve_cpuid_base | CPUID_BHYVE_FEATURES;



	if (bhyve_cpuid_max < cpuid_leaf)

		return 0;



	return cpuid_eax(cpuid_leaf);

}



static bool __init bhyve_ext_dest_id(void)

{

	return !!(bhyve_features() & CPUID_BHYVE_FEAT_EXT_DEST_ID);

}



static bool __init bhyve_x2apic_available(void)

{

	return true;

}



const struct hypervisor_x86 x86_hyper_bhyve __refconst = {

	.name			= "Bhyve",

	.detect			= bhyve_detect,

	.init.init_platform	= x86_init_noop,

	.init.x2apic_available	= bhyve_x2apic_available,

	.init.msi_ext_dest_id	= bhyve_ext_dest_id,

};

arch/x86/kernel/cpu/hypervisor.c

+3 −0
Original line number Diff line number Diff line
@@ -45,6 +45,9 @@ static const __initconst struct hypervisor_x86 * const hypervisors[] = 
#ifdef CONFIG_ACRN_GUEST

	&x86_hyper_acrn,

#endif

#ifdef CONFIG_BHYVE_GUEST

	&x86_hyper_bhyve,

#endif

};



enum x86_hypervisor_type x86_hyper_type;