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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     Tianyu Lan <ltykernel@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>, "hpa@zytor.com" <hpa@zytor.com>,
        "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
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CC:     Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>
Subject: RE: [PATCH 2/9] x86/hyperv: Set Virtual Trust Level in VMBus init
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Thread-Topic: [PATCH 2/9] x86/hyperv: Set Virtual Trust Level in VMBus init
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Thread-Index: AQHZlJwOs5XRKcZuvEKgWk5lE+JQC6+A6Vvg
Date:   Thu, 8 Jun 2023 13:06:09 +0000
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From: Tianyu Lan <ltykernel@gmail.com> Sent: Thursday, June 1, 2023 8:16 AM
>=20
> SEV-SNP guest provides vtl(Virtual Trust Level) and
> get it from Hyper-V hvcall via register hvcall HVCALL_
> GET_VP_REGISTERS.
>=20
> During initialization of VMBus, vtl needs to be set in the
> VMBus init message.

Let's clean up this commit message a bit.  I would suggest:

SEV-SNP guests on Hyper-V can run at multiple Virtual Trust
Levels (VTL).  During boot, get the VTL at which we're running
using the GET_VP_REGISTERs hypercall, and save the value
for future use.  Then during VMBus initialization, set the VTL
with the saved value as required in the VMBus init message.

Michael

>=20
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  arch/x86/hyperv/hv_init.c          | 36 ++++++++++++++++++++++++++++++
>  arch/x86/include/asm/hyperv-tlfs.h |  7 ++++++
>  drivers/hv/connection.c            |  1 +
>  include/asm-generic/mshyperv.h     |  1 +
>  include/linux/hyperv.h             |  4 ++--
>  5 files changed, 47 insertions(+), 2 deletions(-)
>=20
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index a5f9474f08e1..b4a2327c823b 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -378,6 +378,40 @@ static void __init hv_get_partition_id(void)
>  	local_irq_restore(flags);
>  }
>=20
> +static u8 __init get_vtl(void)
> +{
> +	u64 control =3D HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_REGISTERS;
> +	struct hv_get_vp_registers_input *input;
> +	struct hv_get_vp_registers_output *output;
> +	u64 vtl =3D 0;
> +	u64 ret;
> +	unsigned long flags;
> +
> +	local_irq_save(flags);
> +	input =3D *this_cpu_ptr(hyperv_pcpu_input_arg);
> +	output =3D (struct hv_get_vp_registers_output *)input;
> +	if (!input) {
> +		local_irq_restore(flags);
> +		goto done;
> +	}
> +
> +	memset(input, 0, struct_size(input, element, 1));
> +	input->header.partitionid =3D HV_PARTITION_ID_SELF;
> +	input->header.vpindex =3D HV_VP_INDEX_SELF;
> +	input->header.inputvtl =3D 0;
> +	input->element[0].name0 =3D HV_X64_REGISTER_VSM_VP_STATUS;
> +
> +	ret =3D hv_do_hypercall(control, input, output);
> +	if (hv_result_success(ret))
> +		vtl =3D output->as64.low & HV_X64_VTL_MASK;
> +	else
> +		pr_err("Hyper-V: failed to get VTL! %lld", ret);
> +	local_irq_restore(flags);
> +
> +done:
> +	return vtl;
> +}
> +
>  /*
>   * This function is to be invoked early in the boot sequence after the
>   * hypervisor has been detected.
> @@ -506,6 +540,8 @@ void __init hyperv_init(void)
>  	/* Query the VMs extended capability once, so that it can be cached. */
>  	hv_query_ext_cap(0);
>=20
> +	/* Find the VTL */
> +	ms_hyperv.vtl =3D get_vtl();
>  	return;
>=20
>  clean_guest_os_id:
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hy=
perv-tlfs.h
> index cea95dcd27c2..4bf0b315b0ce 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -301,6 +301,13 @@ enum hv_isolation_type {
>  #define HV_X64_MSR_TIME_REF_COUNT	HV_REGISTER_TIME_REF_COUNT
>  #define HV_X64_MSR_REFERENCE_TSC	HV_REGISTER_REFERENCE_TSC
>=20
> +/*
> + * Registers are only accessible via HVCALL_GET_VP_REGISTERS hvcall and
> + * there is not associated MSR address.
> + */
> +#define	HV_X64_REGISTER_VSM_VP_STATUS	0x000D0003
> +#define	HV_X64_VTL_MASK			GENMASK(3, 0)
> +
>  /* Hyper-V memory host visibility */
>  enum hv_mem_host_visibility {
>  	VMBUS_PAGE_NOT_VISIBLE		=3D 0,
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 5978e9dbc286..02b54f85dc60 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -98,6 +98,7 @@ int vmbus_negotiate_version(struct vmbus_channel_msginf=
o
> *msginfo, u32 version)
>  	 */
>  	if (version >=3D VERSION_WIN10_V5) {
>  		msg->msg_sint =3D VMBUS_MESSAGE_SINT;
> +		msg->msg_vtl =3D ms_hyperv.vtl;
>  		vmbus_connection.msg_conn_id =3D VMBUS_MESSAGE_CONNECTION_ID_4;
>  	} else {
>  		msg->interrupt_page =3D virt_to_phys(vmbus_connection.int_page);
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyper=
v.h
> index d444f831d633..c7a90f91c0d3 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -54,6 +54,7 @@ struct ms_hyperv_info {
>  		};
>  	};
>  	u64 shared_gpa_boundary;
> +	u8 vtl;
>  };
>  extern struct ms_hyperv_info ms_hyperv;
>  extern bool hv_nested;
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index bfbc37ce223b..1f2bfec4abde 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -665,8 +665,8 @@ struct vmbus_channel_initiate_contact {
>  		u64 interrupt_page;
>  		struct {
>  			u8	msg_sint;
> -			u8	padding1[3];
> -			u32	padding2;
> +			u8	msg_vtl;
> +			u8	reserved[6];
>  		};
>  	};
>  	u64 monitor_page1;
> --
> 2.25.1