RE: [RFC PATCH V4 03/17] x86/hyperv: Set Virtual Trust Level in VMBus init message

[Michael Kelley (LINUX)]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Monday, April 3, 2023 10:44 AM
> 
> sev-snp guest provides vtl(Virtual Trust Level) and
> get it from hyperv hvcall via HVCALL_GET_VP_REGISTERS.
> Set target vtl in the VMBus init message.
> 
> Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
> ---
> Change since RFC v3:
>        * Use the standard helper functions to check hypercall result
>        * Fix coding style
> 
> Change since RFC v2:
>        * Rename get_current_vtl() to get_vtl()
>        * Fix some coding style issues
> ---
>  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     |  2 ++
>  include/linux/hyperv.h             |  4 ++--
>  5 files changed, 48 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 9f3e2d71d015..7602db5ad4aa 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -384,6 +384,40 @@ static void __init hv_get_partition_id(void)
>  	local_irq_restore(flags);
>  }
> 
> +static u8 __init get_vtl(void)
> +{
> +	u64 control = 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 = 0;
> +	u64 ret;
> +	unsigned long flags;
> +
> +	local_irq_save(flags);
> +	input = *(struct hv_get_vp_registers_input **)this_cpu_ptr(hyperv_pcpu_input_arg);

The cast to struct hv_get_vp_registers_input isn't needed here.  Just do:

	input = *this_cpu_ptr(hyperv_pcpu_input_arg);

I know we have other code that references hyperv_pcpu_input_arg with a more
complicated code sequence, but it's really not necessary.  At some point, we
should go back and clean those up, but let's not add any new cases. :-)


> +	output = (struct hv_get_vp_registers_output *)input;
> +	if (!input) {
> +		local_irq_restore(flags);
> +		goto done;
> +	}
> +
> +	memset(input, 0, sizeof(*input) + sizeof(input->element[0]));

Use struct_size() to calculate the size of a structure plus a trailing
variable size array.

> +	input->header.partitionid = HV_PARTITION_ID_SELF;
> +	input->header.vpindex = HV_VP_INDEX_SELF;
> +	input->header.inputvtl = 0;
> +	input->element[0].name0 = HV_X64_REGISTER_VSM_VP_STATUS;
> +
> +	ret = hv_do_hypercall(control, input, output);
> +	if (hv_result_success(ret))
> +		vtl = output->as64.low & HV_X64_VTL_MASK;
> +	else
> +		pr_err("Hyper-V: failed to get VTL!");

Let's include the hypercall status in the failure message.  If a failure ever
happens, we will really want to know what that status is.  :-)

> +	local_irq_restore(flags);
> +
> +done:
> +	return vtl;
> +}
> +
>  /*
>   * This function is to be invoked early in the boot sequence after the
>   * hypervisor has been detected.
> @@ -512,6 +546,8 @@ void __init hyperv_init(void)
>  	/* Query the VMs extended capability once, so that it can be cached. */
>  	hv_query_ext_cap(0);
> 
> +	/* Find the VTL */
> +	ms_hyperv.vtl = get_vtl();
>  	return;
> 
>  clean_guest_os_id:
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index b4fb75bd1013..3d3f014976e8 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
> 
> +/*
> + * 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		= 0,
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index f670cfd2e056..e4c39f4016ad 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -98,6 +98,7 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
>  	 */
>  	if (version >= VERSION_WIN10_V5) {
>  		msg->msg_sint = VMBUS_MESSAGE_SINT;
> +		msg->msg_vtl = ms_hyperv.vtl;
>  		vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID_4;
>  	} else {
>  		msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index afcd9ae9588c..f91fb06634f0 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -48,6 +48,7 @@ struct ms_hyperv_info {
>  		};
>  	};
>  	u64 shared_gpa_boundary;
> +	u8 vtl;
>  };
>  extern struct ms_hyperv_info ms_hyperv;
>  extern bool hv_nested;
> @@ -58,6 +59,7 @@ extern void * __percpu *hyperv_pcpu_output_arg;
>  extern u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
>  extern u64 hv_do_fast_hypercall8(u16 control, u64 input8);
>  extern bool hv_isolation_type_snp(void);
> +extern bool hv_isolation_type_en_snp(void);

Why is this extern added as part of this patch?  There are not any new
references to hv_isolation_type_en_snp() that would need it.

> 
>  /* Helper functions that provide a consistent pattern for checking Hyper-V hypercall status. */
>  static inline int hv_result(u64 status)
> 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