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Message-ID: <140183ef0ad52cf0f5f892409d362f1ed09129f3.camel@infradead.org>
Date: Thu, 14 Aug 2025 13:22:53 +0200
From: David Woodhouse <dwmw2@...radead.org>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, 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
Cc: Konstantin Belousov <kib@....kiev.ua>, John Baldwin <jhb@...ebsd.org>,
"<cperciva@...snap.com>"
<cperciva@...snap.com>
Subject: [PATCH v2] x86/bhyve: Detect FreeBSD Bhyve hypervisor
From: David Woodhouse <dwmw@...zon.co.uk>
This detects the Bhyve hypervisor and enables 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
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
arch/x86/Kconfig | 9 +++++
arch/x86/include/asm/hypervisor.h | 2 +
arch/x86/kernel/cpu/Makefile | 1 +
arch/x86/kernel/cpu/bhyve.c | 62 +++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/hypervisor.c | 3 ++
5 files changed, 77 insertions(+)
create mode 100644 arch/x86/kernel/cpu/bhyve.c
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 58d890fe2100..ac1c6df44212 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -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
diff --git a/arch/x86/include/asm/hypervisor.h b/arch/x86/include/asm/hypervisor.h
index e41cbf2ec41d..9ad86a7d13f6 100644
--- a/arch/x86/include/asm/hypervisor.h
+++ b/arch/x86/include/asm/hypervisor.h
@@ -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;
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 1e26179ff18c..2f8a58ef690e 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -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
diff --git a/arch/x86/kernel/cpu/bhyve.c b/arch/x86/kernel/cpu/bhyve.c
new file mode 100644
index 000000000000..45bb5c44788a
--- /dev/null
+++ b/arch/x86/kernel/cpu/bhyve.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * FreeBSD Bhyve guest enlightenments
+ *
+ * Copyright © 2025 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: David Woodhouse <dwmw2@...radead.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 CPUID_BHYVE_FEATURES 1
+
+/* 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 ||
+ !cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
+ return 0;
+
+ bhyve_cpuid_base = cpuid_base_hypervisor("bhyve bhyve ", 0);
+ if (!bhyve_cpuid_base)
+ return 0;
+
+ bhyve_cpuid_max = cpuid_eax(bhyve_cpuid_max);
+ return bhyve_cpuid_max;
+}
+
+static uint32_t bhyve_features(void)
+{
+ if (bhyve_cpuid_max < bhyve_cpuid_base + CPUID_BHYVE_FEATURES)
+ return 0;
+
+ return cpuid_eax(bhyve_cpuid_base + CPUID_BHYVE_FEATURES);
+}
+
+static bool __init bhyve_ext_dest_id(void)
+{
+ return !!(bhyve_features() & CPUID_BHYVE_FEAT_EXT_DEST_ID);
+}
+
+static bool __init bhyve_x2apic_available(void)
+{
+ /* Bhyve has always supported x2apic */
+ 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,
+};
diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c
index 553bfbfc3a1b..f3e9219845e8 100644
--- a/arch/x86/kernel/cpu/hypervisor.c
+++ b/arch/x86/kernel/cpu/hypervisor.c
@@ -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;
--
2.49.0
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