There is no definition of the output structure for the
GetVpRegisters hypercall. Hence, using the hypercall
is not possible when the output value has some structure
to it. Even getting a datum of a primitive type reads
as ad-hoc without that definition.

Define struct hv_output_get_vp_registers to enable using
the GetVpRegisters hypercall. Make provisions for all
supported architectures. No functional changes.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
---
 include/hyperv/hvgdk_mini.h | 58 +++++++++++++++++++++++++++++++++++--
 1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index db3d1aaf7330..31c11550af73 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -781,6 +781,8 @@ struct hv_timer_message_payload {
 	__u64 delivery_time;	/* When the message was delivered */
 } __packed;
 
+#if defined(CONFIG_X86)
+
 struct hv_x64_segment_register {
 	u64 base;
 	u32 limit;
@@ -807,6 +809,8 @@ struct hv_x64_table_register {
 	u64 base;
 } __packed;
 
+#endif
+
 union hv_input_vtl {
 	u8 as_uint8;
 	struct {
@@ -1068,6 +1072,41 @@ union hv_dispatch_suspend_register {
 	} __packed;
 };
 
+#if defined(CONFIG_ARM64)
+
+union hv_arm64_pending_interruption_register {
+	u64 as_uint64;
+	struct {
+		u64 interruption_pending : 1;
+		u64 interruption_type : 1;
+		u64 reserved : 30;
+		u32 error_code;
+	} __packed;
+};
+
+union hv_arm64_interrupt_state_register {
+	u64 as_uint64;
+	struct {
+		u64 interrupt_shadow : 1;
+		u64 reserved : 63;
+	} __packed;
+};
+
+union hv_arm64_pending_synthetic_exception_event {
+	u64 as_uint64[2];
+	struct {
+		u32 event_pending : 1;
+		u32 event_type : 3;
+		u32 reserved : 4;
+		u32 exception_type;
+		u64 context;
+	} __packed;
+};
+
+#endif
+
+#if defined(CONFIG_X86)
+
 union hv_x64_interrupt_state_register {
 	u64 as_uint64;
 	struct {
@@ -1091,6 +1130,8 @@ union hv_x64_pending_interruption_register {
 	} __packed;
 };
 
+#endif
+
 union hv_register_value {
 	struct hv_u128 reg128;
 	u64 reg64;
@@ -1098,13 +1139,26 @@ union hv_register_value {
 	u16 reg16;
 	u8 reg8;
 
-	struct hv_x64_segment_register segment;
-	struct hv_x64_table_register table;
 	union hv_explicit_suspend_register explicit_suspend;
 	union hv_intercept_suspend_register intercept_suspend;
 	union hv_dispatch_suspend_register dispatch_suspend;
+#if defined(CONFIG_X86)
+	struct hv_x64_segment_register segment;
+	struct hv_x64_table_register table;
 	union hv_x64_interrupt_state_register interrupt_state;
 	union hv_x64_pending_interruption_register pending_interruption;
+#elif defined(CONFIG_ARM64)
+	union hv_arm64_pending_interruption_register pending_interruption;
+	union hv_arm64_interrupt_state_register interrupt_state;
+	union hv_arm64_pending_synthetic_exception_event pending_synthetic_exception_event;
+#else
+	#error "This architecture is not supported"
+#endif
+};
+
+/* NOTE: Linux helper struct - NOT from Hyper-V code */
+struct hv_output_get_vp_registers {
+	DECLARE_FLEX_ARRAY(union hv_register_value, values);
 };
 
 #if defined(CONFIG_ARM64)
-- 
2.34.1

On 12/26/2024 1:31 PM, Roman Kisel wrote:
> There is no definition of the output structure for the
> GetVpRegisters hypercall. Hence, using the hypercall
> is not possible when the output value has some structure
> to it. Even getting a datum of a primitive type reads
> as ad-hoc without that definition.
> 
> Define struct hv_output_get_vp_registers to enable using
> the GetVpRegisters hypercall. Make provisions for all
> supported architectures. No functional changes.
> 
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
>  include/hyperv/hvgdk_mini.h | 58 +++++++++++++++++++++++++++++++++++--
>  1 file changed, 56 insertions(+), 2 deletions(-)
> 
>  	struct {
> @@ -1091,6 +1130,8 @@ union hv_x64_pending_interruption_register {
>  	} __packed;
>  };
>  
> +#endif
> +
>  union hv_register_value {
>  	struct hv_u128 reg128;
>  	u64 reg64;
> @@ -1098,13 +1139,26 @@ union hv_register_value {
>  	u16 reg16;
>  	u8 reg8;
>  
> -	struct hv_x64_segment_register segment;
> -	struct hv_x64_table_register table;
>  	union hv_explicit_suspend_register explicit_suspend;
>  	union hv_intercept_suspend_register intercept_suspend;
>  	union hv_dispatch_suspend_register dispatch_suspend;
> +#if defined(CONFIG_X86)
> +	struct hv_x64_segment_register segment;
> +	struct hv_x64_table_register table;
>  	union hv_x64_interrupt_state_register interrupt_state;
>  	union hv_x64_pending_interruption_register pending_interruption;
> +#elif defined(CONFIG_ARM64)
> +	union hv_arm64_pending_interruption_register pending_interruption;
> +	union hv_arm64_interrupt_state_register interrupt_state;
> +	union hv_arm64_pending_synthetic_exception_event pending_synthetic_exception_event;
> +#else
> +	#error "This architecture is not supported"
> +#endif
> +};

I don't love the #error for unsupported architectures when Kconfig takes
care of that for us, but I suppose it's for completeness since the arm64
members have to be conditioned on CONFIG_ARM64?

> +
> +/* NOTE: Linux helper struct - NOT from Hyper-V code */
> +struct hv_output_get_vp_registers {
> +	DECLARE_FLEX_ARRAY(union hv_register_value, values);
>  };

I'm not super familiar with DECLARE_FLEX_ARRAY() but it appears this
needs to be wrapped in an anonymous struct at the least per this comment
for the definition of DECLARE_FLEX_ARRAY()

> * In order to have a flexible array member [...] alone in a
> * struct, it needs to be wrapped in an anonymous struct with at least 1
> * named member, but that member can be empty.

Nuno, since you seem to be more familiar, can you provide some guidance?

Thanks,
Easwar

On 12/26/2024 2:11 PM, Easwar Hariharan wrote:
> On 12/26/2024 1:31 PM, Roman Kisel wrote:

[...]

>> +#else
>> +	#error "This architecture is not supported"
>> +#endif
>> +};
> 
> I don't love the #error for unsupported architectures when Kconfig takes
> care of that for us, but I suppose it's for completeness since the arm64
> members have to be conditioned on CONFIG_ARM64?
> 
Felt right to do that, but because it raises questions, it should carry
a comment or be removed as, if you pointed out, Kconfig is in charge of
that kind of validation. As Kconfig permits Hyper-V on the correct set
of arch'es, the best choice would be to remove I think.

>> +
>> +/* NOTE: Linux helper struct - NOT from Hyper-V code */
>> +struct hv_output_get_vp_registers {
>> +	DECLARE_FLEX_ARRAY(union hv_register_value, values);
>>   };
> 
> I'm not super familiar with DECLARE_FLEX_ARRAY() but it appears this
> needs to be wrapped in an anonymous struct at the least per this comment
> for the definition of DECLARE_FLEX_ARRAY()
> 
>> * In order to have a flexible array member [...] alone in a
>> * struct, it needs to be wrapped in an anonymous struct with at least 1
>> * named member, but that member can be empty.
> 
> Nuno, since you seem to be more familiar, can you provide some guidance?
I will wrap the struct member of the documentation requires, not to
make the code look suspicious.

> 
> Thanks,
> Easwar

-- 
Thank you,
Roman