Commit bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
changed the type of the output pointer to `struct hv_register_assoc` from
`struct hv_get_vp_registers_output`. That leads to an incorrect computation,
and leaves the system broken.

Use the correct pointer type for the output of the GetVpRegisters hypercall.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
---
 arch/x86/hyperv/hv_init.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 3cf2a227d666..ba469d6b8250 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -416,13 +416,13 @@ static u8 __init get_vtl(void)
 {
 	u64 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_REGISTERS;
 	struct hv_input_get_vp_registers *input;
-	struct hv_register_assoc *output;
+	struct hv_output_get_vp_registers *output;
 	unsigned long flags;
 	u64 ret;
 
 	local_irq_save(flags);
 	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
-	output = (struct hv_register_assoc *)input;
+	output = (struct hv_output_get_vp_registers *)input;
 
 	memset(input, 0, struct_size(input, names, 1));
 	input->partition_id = HV_PARTITION_ID_SELF;
@@ -432,7 +432,7 @@ static u8 __init get_vtl(void)
 
 	ret = hv_do_hypercall(control, input, output);
 	if (hv_result_success(ret)) {
-		ret = output->value.reg8 & HV_X64_VTL_MASK;
+		ret = output->values[0].reg8 & HV_X64_VTL_MASK;
 	} else {
 		pr_err("Failed to get VTL(error: %lld) exiting...\n", ret);
 		BUG();
-- 
2.34.1

On 12/26/2024 1:31 PM, Roman Kisel wrote:
> Commit bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
> changed the type of the output pointer to `struct hv_register_assoc` from
> `struct hv_get_vp_registers_output`. That leads to an incorrect computation,
> and leaves the system broken.
> 
> Use the correct pointer type for the output of the GetVpRegisters hypercall.
> 
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
>  arch/x86/hyperv/hv_init.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)


Please add a Fixes tag, you can just reply to this email, tooling would
probably pick it up. Assuming that:

Reviewed-by: Easwar Hariharan <eahariha@linux.microsoft.com>