Re: [PATCH 1/2] hyperv: Fix pointer type for the output of the hypercall in get_vtl(void)

[Roman Kisel]

On 12/19/2024 10:40 AM, Nuno Das Neves wrote:

On 12/18/2024 12:54 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.

My bad! But, lets not use `struct hv_get_registers_output`. Instead, use
`struct hv_register_value`, since that is the more complete definition of a
register value. The output of the get_vp_registers hypercall is just an array
of these values.

Ideally we remove `struct hv_get_vp_registers_output` at some point, since
it serves the same role as `struct hv_register_value` but in a more limited
capacity.

Nuno, thank you very much for your help! Agreed, I will use `struct
 hv_register_value` in v2.

Thanks
Nuno

Thank you,
Roman

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

Fixes: bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
Signed-off-by: Roman Kisel <rom...@linux.microsoft.com>
---
  arch/x86/hyperv/hv_init.c   | 6 +++---
  include/hyperv/hvgdk_mini.h | 3 ---
  2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 3cf2a227d666..c7185c6a290b 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_get_vp_registers_output *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_get_vp_registers_output *)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->as64.low & HV_X64_VTL_MASK;
        } else {
                pr_err("Failed to get VTL(error: %lld) exiting...\n", ret);
                BUG();
diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index db3d1aaf7330..0b1a10828f33 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -1107,7 +1107,6 @@ union hv_register_value {
        union hv_x64_pending_interruption_register pending_interruption;
  };

-#if defined(CONFIG_ARM64)

  /* HvGetVpRegisters returns an array of these output elements */
  struct hv_get_vp_registers_output {
        union {
@@ -1124,8 +1123,6 @@ struct hv_get_vp_registers_output {
        };
  };

-#endif /* CONFIG_ARM64 */

-
  struct hv_register_assoc {
        u32 name;                       /* enum hv_register_name */
        u32 reserved1;

--
Thank you,
Roman