[RFC PATCH 06/17] x86/hyperv: Get Virtual Trust Level via hvcall

[Tianyu Lan <ltykernel@xxxxxxxxx>]

From: Tianyu Lan <tiala@xxxxxxxxxxxxx>

sev-snp guest provides vtl(Virtual Trust Level) and get it from
hyperv hvcall via HVCALL_GET_VP_REGISTERS.

Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
---
 arch/x86/hyperv/hv_init.c      | 35 ++++++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 4600c5941957..5b919d4d24c0 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -390,6 +390,39 @@ static void __init hv_get_partition_id(void)
 	local_irq_restore(flags);
 }
 
+static u8 __init get_current_vtl(void)
+{
+	u64 control = ((u64)1 << HV_HYPERCALL_REP_COMP_OFFSET) | HVCALL_GET_VP_REGISTERS;
+	struct hv_get_vp_registers_input *input = NULL;
+	struct hv_get_vp_registers_output *output = NULL;
+	u8 vtl = 0;
+	int ret;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	input = *(struct hv_get_vp_registers_input **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	output = (struct hv_get_vp_registers_output *)input;
+	if (!input || !output) {
+		pr_err("Hyper-V: cannot allocate a shared page!");
+		goto done;
+	}
+
+	memset(input, 0, sizeof(*input) + sizeof(input->element[0]));
+	input->header.partitionid = HV_PARTITION_ID_SELF;
+	input->header.inputvtl = 0;
+	input->element[0].name0 = 0x000D0003;
+
+	ret = hv_do_hypercall(control, input, output);
+	if (ret == 0)
+		vtl = output->as64.low & 0xf;
+	else
+		pr_err("Hyper-V: failed to get the current VTL!");
+	local_irq_restore(flags);
+
+done:
+	return vtl;
+}
+
 /*
  * This function is to be invoked early in the boot sequence after the
  * hypervisor has been detected.
@@ -527,6 +560,8 @@ void __init hyperv_init(void)
 	if (hv_is_isolation_supported())
 		swiotlb_update_mem_attributes();
 #endif
+	/* Find the current VTL */
+	ms_hyperv.vtl = get_current_vtl();
 
 	return;
 
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index bfb9eb9d7215..68133de044ec 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -46,6 +46,7 @@ struct ms_hyperv_info {
 		};
 	};
 	u64 shared_gpa_boundary;
+	u8 vtl;
 };
 extern struct ms_hyperv_info ms_hyperv;
 
@@ -55,6 +56,7 @@ 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);
 
 /* Helper functions that provide a consistent pattern for checking Hyper-V hypercall status. */
 static inline int hv_result(u64 status)
-- 
2.25.1