diff mbox series

[v11,3/5] arm64: hyperv: Initialize hypervisor on boot

Message ID 1626793023-13830-4-git-send-email-mikelley@microsoft.com (mailing list archive)
State New, archived
Headers show
Series Enable Linux guests on Hyper-V on ARM64 | expand

Commit Message

Michael Kelley (LINUX) July 20, 2021, 2:57 p.m. UTC
Add ARM64-specific code to initialize the Hyper-V
hypervisor when booting as a guest VM.

This code is built only when CONFIG_HYPERV is enabled.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/arm64/hyperv/Makefile   |  2 +-
 arch/arm64/hyperv/mshyperv.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/hyperv/mshyperv.c

Comments

Boqun Feng July 21, 2021, 2:55 p.m. UTC | #1
On Tue, Jul 20, 2021 at 07:57:01AM -0700, Michael Kelley wrote:
> Add ARM64-specific code to initialize the Hyper-V
> hypervisor when booting as a guest VM.
> 
> This code is built only when CONFIG_HYPERV is enabled.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>

FWIW,

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

Regards,
Boqun

> ---
>  arch/arm64/hyperv/Makefile   |  2 +-
>  arch/arm64/hyperv/mshyperv.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 84 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/hyperv/mshyperv.c
> 
> diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
> index 1697d30..87c31c0 100644
> --- a/arch/arm64/hyperv/Makefile
> +++ b/arch/arm64/hyperv/Makefile
> @@ -1,2 +1,2 @@
>  # SPDX-License-Identifier: GPL-2.0
> -obj-y		:= hv_core.o
> +obj-y		:= hv_core.o mshyperv.o
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> new file mode 100644
> index 0000000..2811fd0
> --- /dev/null
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Core routines for interacting with Microsoft's Hyper-V hypervisor,
> + * including hypervisor initialization.
> + *
> + * Copyright (C) 2021, Microsoft, Inc.
> + *
> + * Author : Michael Kelley <mikelley@microsoft.com>
> + */
> +
> +#include <linux/types.h>
> +#include <linux/acpi.h>
> +#include <linux/export.h>
> +#include <linux/errno.h>
> +#include <linux/version.h>
> +#include <linux/cpuhotplug.h>
> +#include <asm/mshyperv.h>
> +
> +static bool hyperv_initialized;
> +
> +static int __init hyperv_init(void)
> +{
> +	struct hv_get_vp_registers_output	result;
> +	u32	a, b, c, d;
> +	u64	guest_id;
> +	int	ret;
> +
> +	/*
> +	 * If we're in a VM on Hyper-V, the ACPI hypervisor_id field will
> +	 * have the string "MsHyperV".
> +	 */
> +	if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
> +		return -EINVAL;
> +
> +	/* Setup the guest ID */
> +	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
> +	hv_set_vpreg(HV_REGISTER_GUEST_OSID, guest_id);
> +
> +	/* Get the features and hints from Hyper-V */
> +	hv_get_vpreg_128(HV_REGISTER_FEATURES, &result);
> +	ms_hyperv.features = result.as32.a;
> +	ms_hyperv.priv_high = result.as32.b;
> +	ms_hyperv.misc_features = result.as32.c;
> +
> +	hv_get_vpreg_128(HV_REGISTER_ENLIGHTENMENTS, &result);
> +	ms_hyperv.hints = result.as32.a;
> +
> +	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
> +		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
> +		ms_hyperv.misc_features);
> +
> +	/* Get information about the Hyper-V host version */
> +	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, &result);
> +	a = result.as32.a;
> +	b = result.as32.b;
> +	c = result.as32.c;
> +	d = result.as32.d;
> +	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
> +		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
> +
> +	ret = hv_common_init();
> +	if (ret)
> +		return ret;
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm64/hyperv_init:online",
> +				hv_common_cpu_init, hv_common_cpu_die);
> +	if (ret < 0) {
> +		hv_common_free();
> +		return ret;
> +	}
> +
> +	hyperv_initialized = true;
> +	return 0;
> +}
> +
> +early_initcall(hyperv_init);
> +
> +bool hv_is_hyperv_initialized(void)
> +{
> +	return hyperv_initialized;
> +}
> +EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
> -- 
> 1.8.3.1
>
Sunil Muthuswamy July 27, 2021, 5:05 p.m. UTC | #2
> Subject: [PATCH v11 3/5] arm64: hyperv: Initialize hypervisor on boot
> 
> Add ARM64-specific code to initialize the Hyper-V
> hypervisor when booting as a guest VM.
> 
> This code is built only when CONFIG_HYPERV is enabled.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  arch/arm64/hyperv/Makefile   |  2 +-
>  arch/arm64/hyperv/mshyperv.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 84 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/hyperv/mshyperv.c
> 
> diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
> index 1697d30..87c31c0 100644
> --- a/arch/arm64/hyperv/Makefile
> +++ b/arch/arm64/hyperv/Makefile
> @@ -1,2 +1,2 @@
>  # SPDX-License-Identifier: GPL-2.0
> -obj-y		:= hv_core.o
> +obj-y		:= hv_core.o mshyperv.o
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> new file mode 100644
> index 0000000..2811fd0
> --- /dev/null
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Core routines for interacting with Microsoft's Hyper-V hypervisor,
> + * including hypervisor initialization.
> + *
> + * Copyright (C) 2021, Microsoft, Inc.
> + *
> + * Author : Michael Kelley <mikelley@microsoft.com>
> + */
> +
> +#include <linux/types.h>
> +#include <linux/acpi.h>
> +#include <linux/export.h>
> +#include <linux/errno.h>
> +#include <linux/version.h>
> +#include <linux/cpuhotplug.h>
> +#include <asm/mshyperv.h>
> +
> +static bool hyperv_initialized;
> +
> +static int __init hyperv_init(void)
> +{
> +	struct hv_get_vp_registers_output	result;
> +	u32	a, b, c, d;
> +	u64	guest_id;
> +	int	ret;
> +
> +	/*
> +	 * If we're in a VM on Hyper-V, the ACPI hypervisor_id field will
> +	 * have the string "MsHyperV".
> +	 */
> +	if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
> +		return -EINVAL;
> +
> +	/* Setup the guest ID */
> +	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
> +	hv_set_vpreg(HV_REGISTER_GUEST_OSID, guest_id);
> +
> +	/* Get the features and hints from Hyper-V */
> +	hv_get_vpreg_128(HV_REGISTER_FEATURES, &result);
> +	ms_hyperv.features = result.as32.a;
> +	ms_hyperv.priv_high = result.as32.b;
> +	ms_hyperv.misc_features = result.as32.c;
> +
> +	hv_get_vpreg_128(HV_REGISTER_ENLIGHTENMENTS, &result);
> +	ms_hyperv.hints = result.as32.a;
> +
> +	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
> +		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
> +		ms_hyperv.misc_features);
> +
> +	/* Get information about the Hyper-V host version */
> +	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, &result);
> +	a = result.as32.a;
> +	b = result.as32.b;
> +	c = result.as32.c;
> +	d = result.as32.d;
> +	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
> +		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
> +
> +	ret = hv_common_init();
> +	if (ret)
> +		return ret;
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm64/hyperv_init:online",
> +				hv_common_cpu_init, hv_common_cpu_die);
> +	if (ret < 0) {
> +		hv_common_free();
> +		return ret;
> +	}
> +
> +	hyperv_initialized = true;
> +	return 0;
> +}
> +
> +early_initcall(hyperv_init);
> +
> +bool hv_is_hyperv_initialized(void)
> +{
> +	return hyperv_initialized;
> +}
> +EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
> --
> 1.8.3.1

Reviewed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Marc Zyngier Aug. 2, 2021, 3:55 p.m. UTC | #3
On Tue, 20 Jul 2021 15:57:01 +0100,
Michael Kelley <mikelley@microsoft.com> wrote:
> 
> Add ARM64-specific code to initialize the Hyper-V
> hypervisor when booting as a guest VM.
> 
> This code is built only when CONFIG_HYPERV is enabled.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  arch/arm64/hyperv/Makefile   |  2 +-
>  arch/arm64/hyperv/mshyperv.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 84 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/hyperv/mshyperv.c
> 
> diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
> index 1697d30..87c31c0 100644
> --- a/arch/arm64/hyperv/Makefile
> +++ b/arch/arm64/hyperv/Makefile
> @@ -1,2 +1,2 @@
>  # SPDX-License-Identifier: GPL-2.0
> -obj-y		:= hv_core.o
> +obj-y		:= hv_core.o mshyperv.o
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> new file mode 100644
> index 0000000..2811fd0
> --- /dev/null
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Core routines for interacting with Microsoft's Hyper-V hypervisor,
> + * including hypervisor initialization.
> + *
> + * Copyright (C) 2021, Microsoft, Inc.
> + *
> + * Author : Michael Kelley <mikelley@microsoft.com>
> + */
> +
> +#include <linux/types.h>
> +#include <linux/acpi.h>
> +#include <linux/export.h>
> +#include <linux/errno.h>
> +#include <linux/version.h>
> +#include <linux/cpuhotplug.h>
> +#include <asm/mshyperv.h>
> +
> +static bool hyperv_initialized;
> +
> +static int __init hyperv_init(void)
> +{
> +	struct hv_get_vp_registers_output	result;
> +	u32	a, b, c, d;
> +	u64	guest_id;
> +	int	ret;
> +
> +	/*
> +	 * If we're in a VM on Hyper-V, the ACPI hypervisor_id field will
> +	 * have the string "MsHyperV".
> +	 */
> +	if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
> +		return -EINVAL;

Before going ahead and parsing the local FADT copy, it would be
prudent to test that you are actually on an ACPI system, specially
given that this function is unconditionally called, even on DT
systems.  In the same vein, returning -EINVAL when failing to find
Hyper-V is a bit excessive.

> +
> +	/* Setup the guest ID */
> +	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
> +	hv_set_vpreg(HV_REGISTER_GUEST_OSID, guest_id);
> +
> +	/* Get the features and hints from Hyper-V */
> +	hv_get_vpreg_128(HV_REGISTER_FEATURES, &result);
> +	ms_hyperv.features = result.as32.a;
> +	ms_hyperv.priv_high = result.as32.b;
> +	ms_hyperv.misc_features = result.as32.c;
> +
> +	hv_get_vpreg_128(HV_REGISTER_ENLIGHTENMENTS, &result);
> +	ms_hyperv.hints = result.as32.a;
> +
> +	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
> +		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
> +		ms_hyperv.misc_features);
> +
> +	/* Get information about the Hyper-V host version */
> +	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, &result);
> +	a = result.as32.a;
> +	b = result.as32.b;
> +	c = result.as32.c;
> +	d = result.as32.d;
> +	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
> +		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
> +
> +	ret = hv_common_init();
> +	if (ret)
> +		return ret;
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm64/hyperv_init:online",
> +				hv_common_cpu_init, hv_common_cpu_die);
> +	if (ret < 0) {
> +		hv_common_free();
> +		return ret;
> +	}
> +
> +	hyperv_initialized = true;
> +	return 0;
> +}
> +
> +early_initcall(hyperv_init);
> +
> +bool hv_is_hyperv_initialized(void)
> +{
> +	return hyperv_initialized;
> +}
> +EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);

Thanks,

	M.
Mark Rutland Aug. 2, 2021, 4:26 p.m. UTC | #4
On Tue, Jul 20, 2021 at 07:57:01AM -0700, Michael Kelley wrote:
> Add ARM64-specific code to initialize the Hyper-V
> hypervisor when booting as a guest VM.
> 
> This code is built only when CONFIG_HYPERV is enabled.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  arch/arm64/hyperv/Makefile   |  2 +-
>  arch/arm64/hyperv/mshyperv.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 84 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/hyperv/mshyperv.c
> 
> diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
> index 1697d30..87c31c0 100644
> --- a/arch/arm64/hyperv/Makefile
> +++ b/arch/arm64/hyperv/Makefile
> @@ -1,2 +1,2 @@
>  # SPDX-License-Identifier: GPL-2.0
> -obj-y		:= hv_core.o
> +obj-y		:= hv_core.o mshyperv.o
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> new file mode 100644
> index 0000000..2811fd0
> --- /dev/null
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Core routines for interacting with Microsoft's Hyper-V hypervisor,
> + * including hypervisor initialization.
> + *
> + * Copyright (C) 2021, Microsoft, Inc.
> + *
> + * Author : Michael Kelley <mikelley@microsoft.com>
> + */
> +
> +#include <linux/types.h>
> +#include <linux/acpi.h>
> +#include <linux/export.h>
> +#include <linux/errno.h>
> +#include <linux/version.h>
> +#include <linux/cpuhotplug.h>
> +#include <asm/mshyperv.h>
> +
> +static bool hyperv_initialized;
> +
> +static int __init hyperv_init(void)
> +{
> +	struct hv_get_vp_registers_output	result;
> +	u32	a, b, c, d;
> +	u64	guest_id;
> +	int	ret;

As Marc suggests, before looking at the FADT, you need something like:

	/*
	 * Hyper-V VMs always have ACPI.
	 */
	if (acpi_disabled)
		return 0;

... where `acpi_disabled` is defined in <linux/acpi.h> (or via its
includes), so you don't need to include any additional headers.

> +
> +	/*
> +	 * If we're in a VM on Hyper-V, the ACPI hypervisor_id field will
> +	 * have the string "MsHyperV".
> +	 */
> +	if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
> +		return -EINVAL;

As Marc suggests, it's no an error for a platform to not have Hyper-V,
so returning 0 in tihs case would be preferable.

Otherwise this looks fine to me.

Thanks,
Mark.

> +
> +	/* Setup the guest I[D */
> +	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
> +	hv_set_vpreg(HV_REGISTER_GUEST_OSID, guest_id);
> +
> +	/* Get the features and hints from Hyper-V */
> +	hv_get_vpreg_128(HV_REGISTER_FEATURES, &result);
> +	ms_hyperv.features = result.as32.a;
> +	ms_hyperv.priv_high = result.as32.b;
> +	ms_hyperv.misc_features = result.as32.c;
> +
> +	hv_get_vpreg_128(HV_REGISTER_ENLIGHTENMENTS, &result);
> +	ms_hyperv.hints = result.as32.a;
> +
> +	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
> +		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
> +		ms_hyperv.misc_features);
> +
> +	/* Get information about the Hyper-V host version */
> +	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, &result);
> +	a = result.as32.a;
> +	b = result.as32.b;
> +	c = result.as32.c;
> +	d = result.as32.d;
> +	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
> +		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
> +
> +	ret = hv_common_init();
> +	if (ret)
> +		return ret;
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm64/hyperv_init:online",
> +				hv_common_cpu_init, hv_common_cpu_die);
> +	if (ret < 0) {
> +		hv_common_free();
> +		return ret;
> +	}
> +
> +	hyperv_initialized = true;
> +	return 0;
> +}
> +
> +early_initcall(hyperv_init);
> +
> +bool hv_is_hyperv_initialized(void)
> +{
> +	return hyperv_initialized;
> +}
> +EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
> -- 
> 1.8.3.1
>
Michael Kelley (LINUX) Aug. 2, 2021, 5:13 p.m. UTC | #5
From: Mark Rutland <mark.rutland@arm.com> Sent: Monday, August 2, 2021 9:26 AM
> 
> On Tue, Jul 20, 2021 at 07:57:01AM -0700, Michael Kelley wrote:
> > Add ARM64-specific code to initialize the Hyper-V
> > hypervisor when booting as a guest VM.
> >
> > This code is built only when CONFIG_HYPERV is enabled.
> >
> > Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> > ---
> >  arch/arm64/hyperv/Makefile   |  2 +-
> >  arch/arm64/hyperv/mshyperv.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 84 insertions(+), 1 deletion(-)
> >  create mode 100644 arch/arm64/hyperv/mshyperv.c
> >
> > diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
> > index 1697d30..87c31c0 100644
> > --- a/arch/arm64/hyperv/Makefile
> > +++ b/arch/arm64/hyperv/Makefile
> > @@ -1,2 +1,2 @@
> >  # SPDX-License-Identifier: GPL-2.0
> > -obj-y		:= hv_core.o
> > +obj-y		:= hv_core.o mshyperv.o
> > diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> > new file mode 100644
> > index 0000000..2811fd0
> > --- /dev/null
> > +++ b/arch/arm64/hyperv/mshyperv.c
> > @@ -0,0 +1,83 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * Core routines for interacting with Microsoft's Hyper-V hypervisor,
> > + * including hypervisor initialization.
> > + *
> > + * Copyright (C) 2021, Microsoft, Inc.
> > + *
> > + * Author : Michael Kelley <mikelley@microsoft.com>
> > + */
> > +
> > +#include <linux/types.h>
> > +#include <linux/acpi.h>
> > +#include <linux/export.h>
> > +#include <linux/errno.h>
> > +#include <linux/version.h>
> > +#include <linux/cpuhotplug.h>
> > +#include <asm/mshyperv.h>
> > +
> > +static bool hyperv_initialized;
> > +
> > +static int __init hyperv_init(void)
> > +{
> > +	struct hv_get_vp_registers_output	result;
> > +	u32	a, b, c, d;
> > +	u64	guest_id;
> > +	int	ret;
> 
> As Marc suggests, before looking at the FADT, you need something like:
> 
> 	/*
> 	 * Hyper-V VMs always have ACPI.
> 	 */
> 	if (acpi_disabled)
> 		return 0;
> 
> ... where `acpi_disabled` is defined in <linux/acpi.h> (or via its
> includes), so you don't need to include any additional headers.
> 
> > +
> > +	/*
> > +	 * If we're in a VM on Hyper-V, the ACPI hypervisor_id field will
> > +	 * have the string "MsHyperV".
> > +	 */
> > +	if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
> > +		return -EINVAL;
> 
> As Marc suggests, it's no an error for a platform to not have Hyper-V,
> so returning 0 in tihs case would be preferable.
> 
> Otherwise this looks fine to me.
> 

Thanks Marc and Mark.  Good point that the code should cleanly
handle the case where a kernel is built with CONFIG_HYPERV but
running somewhere other than as a Hyper-V guest.

Michael
diff mbox series

Patch

diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
index 1697d30..87c31c0 100644
--- a/arch/arm64/hyperv/Makefile
+++ b/arch/arm64/hyperv/Makefile
@@ -1,2 +1,2 @@ 
 # SPDX-License-Identifier: GPL-2.0
-obj-y		:= hv_core.o
+obj-y		:= hv_core.o mshyperv.o
diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
new file mode 100644
index 0000000..2811fd0
--- /dev/null
+++ b/arch/arm64/hyperv/mshyperv.c
@@ -0,0 +1,83 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Core routines for interacting with Microsoft's Hyper-V hypervisor,
+ * including hypervisor initialization.
+ *
+ * Copyright (C) 2021, Microsoft, Inc.
+ *
+ * Author : Michael Kelley <mikelley@microsoft.com>
+ */
+
+#include <linux/types.h>
+#include <linux/acpi.h>
+#include <linux/export.h>
+#include <linux/errno.h>
+#include <linux/version.h>
+#include <linux/cpuhotplug.h>
+#include <asm/mshyperv.h>
+
+static bool hyperv_initialized;
+
+static int __init hyperv_init(void)
+{
+	struct hv_get_vp_registers_output	result;
+	u32	a, b, c, d;
+	u64	guest_id;
+	int	ret;
+
+	/*
+	 * If we're in a VM on Hyper-V, the ACPI hypervisor_id field will
+	 * have the string "MsHyperV".
+	 */
+	if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
+		return -EINVAL;
+
+	/* Setup the guest ID */
+	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
+	hv_set_vpreg(HV_REGISTER_GUEST_OSID, guest_id);
+
+	/* Get the features and hints from Hyper-V */
+	hv_get_vpreg_128(HV_REGISTER_FEATURES, &result);
+	ms_hyperv.features = result.as32.a;
+	ms_hyperv.priv_high = result.as32.b;
+	ms_hyperv.misc_features = result.as32.c;
+
+	hv_get_vpreg_128(HV_REGISTER_ENLIGHTENMENTS, &result);
+	ms_hyperv.hints = result.as32.a;
+
+	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
+		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
+		ms_hyperv.misc_features);
+
+	/* Get information about the Hyper-V host version */
+	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, &result);
+	a = result.as32.a;
+	b = result.as32.b;
+	c = result.as32.c;
+	d = result.as32.d;
+	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
+		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
+
+	ret = hv_common_init();
+	if (ret)
+		return ret;
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm64/hyperv_init:online",
+				hv_common_cpu_init, hv_common_cpu_die);
+	if (ret < 0) {
+		hv_common_free();
+		return ret;
+	}
+
+	hyperv_initialized = true;
+	return 0;
+}
+
+early_initcall(hyperv_init);
+
+bool hv_is_hyperv_initialized(void)
+{
+	return hyperv_initialized;
+}
+EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);