RE: [PATCH 2/9] x86/hyperv: Set Virtual Trust Level in VMBus init message

Michael Kelley (LINUX)
2023-06-08T13:06:19Z

From: Tianyu Lan <ltykernel@gmail.com> Sent: Thursday, June 1, 2023 8:16 AM
>
> SEV-SNP guest provides vtl(Virtual Trust Level) and
> get it from Hyper-V hvcall via register hvcall HVCALL_
> GET_VP_REGISTERS.
>
> 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

>
> 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(-)
>
> 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);
> }
>
> +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 = *this_cpu_ptr(hyperv_pcpu_input_arg);
> + output = (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 = 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! %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);
>
> + /* 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 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
>
> +/*
> + * 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 5978e9dbc286..02b54f85dc60 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 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