[PATCH v6 2/8] x86/hyperv: Set Virtual Trust Level in VMBus init message

Tianyu Lan
2023-08-16T16:00:10Z

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.

Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
* Change since v5:
Remove hvcall input parameter page check

* Change since v3:
Call get_vtl() when SEV-SNP is available and set vtl to 0
by default if fail to get VTL from Hyper-V.
* Change since v2:
Update the change log.
---
arch/x86/hyperv/hv_init.c | 34 ++++++++++++++++++++++++++++++
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, 45 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 6c04b52f139b..f62ca3f6e9b2 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -378,6 +378,36 @@ 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;
+ unsigned long flags;
+ u64 ret = 0;
+
+ local_irq_save(flags);
+ input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+ output = (struct hv_get_vp_registers_output *)input;
+
+ 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)) {
+ ret = output->as64.low & HV_X64_VTL_MASK;
+ } else {
+ pr_err("Failed to get VTL(%lld) and set VTL to zero by default.\n", ret);
+ ret = 0;
+ }
+
+ local_irq_restore(flags);
+ return ret;
+}
+
/*
* This function is to be invoked early in the boot sequence after the
* hypervisor has been detected.
@@ -506,6 +536,10 @@ 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 */
+ if (hv_isolation_type_en_snp())
+ 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 580c766958de..efd0d2aedad3 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