Re: [PATCH v5 01/10] hyperv: Convert Hyper-V status codes to strings

[Nuno Das Neves]

On 3/6/2025 9:57 AM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> Sent: Wednesday, February 26, 2025 3:08 PM
>>
>> Introduce hv_result_to_string() for this purpose. This allows
>> hypercall failures to be debugged more easily with dmesg.
>>
>> Signed-off-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx>
>> ---
>>  drivers/hv/hv_common.c         | 65 ++++++++++++++++++++++++++++++++++
>>  drivers/hv/hv_proc.c           | 13 ++++---
>>  include/asm-generic/mshyperv.h |  1 +
>>  3 files changed, 74 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
>> index 9804adb4cc56..ce20818688fe 100644
>> --- a/drivers/hv/hv_common.c
>> +++ b/drivers/hv/hv_common.c
>> @@ -740,3 +740,68 @@ void hv_identify_partition_type(void)
>>  			pr_crit("Hyper-V: CONFIG_MSHV_ROOT not enabled!\n");
>>  	}
>>  }
>> +
>> +const char *hv_result_to_string(u64 hv_status)
>> +{
>> +	switch (hv_result(hv_status)) {
>> +	case HV_STATUS_SUCCESS:
>> +		return "HV_STATUS_SUCCESS";
>> +	case HV_STATUS_INVALID_HYPERCALL_CODE:
>> +		return "HV_STATUS_INVALID_HYPERCALL_CODE";
>> +	case HV_STATUS_INVALID_HYPERCALL_INPUT:
>> +		return "HV_STATUS_INVALID_HYPERCALL_INPUT";
>> +	case HV_STATUS_INVALID_ALIGNMENT:
>> +		return "HV_STATUS_INVALID_ALIGNMENT";
>> +	case HV_STATUS_INVALID_PARAMETER:
>> +		return "HV_STATUS_INVALID_PARAMETER";
>> +	case HV_STATUS_ACCESS_DENIED:
>> +		return "HV_STATUS_ACCESS_DENIED";
>> +	case HV_STATUS_INVALID_PARTITION_STATE:
>> +		return "HV_STATUS_INVALID_PARTITION_STATE";
>> +	case HV_STATUS_OPERATION_DENIED:
>> +		return "HV_STATUS_OPERATION_DENIED";
>> +	case HV_STATUS_UNKNOWN_PROPERTY:
>> +		return "HV_STATUS_UNKNOWN_PROPERTY";
>> +	case HV_STATUS_PROPERTY_VALUE_OUT_OF_RANGE:
>> +		return "HV_STATUS_PROPERTY_VALUE_OUT_OF_RANGE";
>> +	case HV_STATUS_INSUFFICIENT_MEMORY:
>> +		return "HV_STATUS_INSUFFICIENT_MEMORY";
>> +	case HV_STATUS_INVALID_PARTITION_ID:
>> +		return "HV_STATUS_INVALID_PARTITION_ID";
>> +	case HV_STATUS_INVALID_VP_INDEX:
>> +		return "HV_STATUS_INVALID_VP_INDEX";
>> +	case HV_STATUS_NOT_FOUND:
>> +		return "HV_STATUS_NOT_FOUND";
>> +	case HV_STATUS_INVALID_PORT_ID:
>> +		return "HV_STATUS_INVALID_PORT_ID";
>> +	case HV_STATUS_INVALID_CONNECTION_ID:
>> +		return "HV_STATUS_INVALID_CONNECTION_ID";
>> +	case HV_STATUS_INSUFFICIENT_BUFFERS:
>> +		return "HV_STATUS_INSUFFICIENT_BUFFERS";
>> +	case HV_STATUS_NOT_ACKNOWLEDGED:
>> +		return "HV_STATUS_NOT_ACKNOWLEDGED";
>> +	case HV_STATUS_INVALID_VP_STATE:
>> +		return "HV_STATUS_INVALID_VP_STATE";
>> +	case HV_STATUS_NO_RESOURCES:
>> +		return "HV_STATUS_NO_RESOURCES";
>> +	case HV_STATUS_PROCESSOR_FEATURE_NOT_SUPPORTED:
>> +		return "HV_STATUS_PROCESSOR_FEATURE_NOT_SUPPORTED";
>> +	case HV_STATUS_INVALID_LP_INDEX:
>> +		return "HV_STATUS_INVALID_LP_INDEX";
>> +	case HV_STATUS_INVALID_REGISTER_VALUE:
>> +		return "HV_STATUS_INVALID_REGISTER_VALUE";
>> +	case HV_STATUS_OPERATION_FAILED:
>> +		return "HV_STATUS_OPERATION_FAILED";
>> +	case HV_STATUS_TIME_OUT:
>> +		return "HV_STATUS_TIME_OUT";
>> +	case HV_STATUS_CALL_PENDING:
>> +		return "HV_STATUS_CALL_PENDING";
>> +	case HV_STATUS_VTL_ALREADY_ENABLED:
>> +		return "HV_STATUS_VTL_ALREADY_ENABLED";
>> +	default:
>> +		return "Unknown";
>> +	};
>> +	return "Unknown";
>> +}
>> +EXPORT_SYMBOL_GPL(hv_result_to_string);
>> +
>> diff --git a/drivers/hv/hv_proc.c b/drivers/hv/hv_proc.c
>> index 2fae18e4f7d2..8fc30f509fa7 100644
>> --- a/drivers/hv/hv_proc.c
>> +++ b/drivers/hv/hv_proc.c
>> @@ -87,7 +87,8 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32
>> num_pages)
>>  				     page_count, 0, input_page, NULL);
>>  	local_irq_restore(flags);
>>  	if (!hv_result_success(status)) {
>> -		pr_err("Failed to deposit pages: %lld\n", status);
>> +		pr_err("%s: Failed to deposit pages: %s\n", __func__,
>> +		       hv_result_to_string(status));
>>  		ret = hv_result_to_errno(status);
>>  		goto err_free_allocations;
>>  	}
>> @@ -137,8 +138,9 @@ int hv_call_add_logical_proc(int node, u32 lp_index, u32 apic_id)
>>
>>  		if (hv_result(status) != HV_STATUS_INSUFFICIENT_MEMORY) {
>>  			if (!hv_result_success(status)) {
>> -				pr_err("%s: cpu %u apic ID %u, %lld\n", __func__,
>> -				       lp_index, apic_id, status);
>> +				pr_err("%s: cpu %u apic ID %u, %s\n",
>> +				       __func__, lp_index, apic_id,
>> +				       hv_result_to_string(status));
>>  				ret = hv_result_to_errno(status);
>>  			}
>>  			break;
>> @@ -179,8 +181,9 @@ int hv_call_create_vp(int node, u64 partition_id, u32 vp_index,
>> u32 flags)
>>
>>  		if (hv_result(status) != HV_STATUS_INSUFFICIENT_MEMORY) {
>>  			if (!hv_result_success(status)) {
>> -				pr_err("%s: vcpu %u, lp %u, %lld\n", __func__,
>> -				       vp_index, flags, status);
>> +				pr_err("%s: vcpu %u, lp %u, %s\n",
>> +				       __func__, vp_index, flags,
>> +				       hv_result_to_string(status));
>>  				ret = hv_result_to_errno(status);
>>  			}
>>  			break;
>> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
>> index b13b0cda4ac8..dc4729dba9ef 100644
>> --- a/include/asm-generic/mshyperv.h
>> +++ b/include/asm-generic/mshyperv.h
>> @@ -298,6 +298,7 @@ static inline int cpumask_to_vpset_skip(struct hv_vpset *vpset,
>>  	return __cpumask_to_vpset(vpset, cpus, func);
>>  }
>>
>> +const char *hv_result_to_string(u64 hv_status);
>>  int hv_result_to_errno(u64 status);
>>  void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
>>  bool hv_is_hyperv_initialized(void);
>> --
>> 2.34.1
> 
> I've read through the other comments on this patch. I definitely vote
> for outputting both the hex code along with a string translation, which
> could be empty if the hex code is unrecognized by the translation code.
> 
> I can see providing something like hv_hvcall_err() as Nuno proposed, since
> that standardizes the text output. But I wonder if it would be too limiting.
> For example, in the changes above, both hv_call_add_logical_proc() and
> hv_call_create_vp() output additional debugging values, which we probably
> don't want to give up.
> 

Good point - that is easy though, I'll add a __VA_ARGS__ to the macro so any
custom message can be printed alongside the other info.

> Lastly, from an implementation standpoint, rather than using a big
> switch statement, build a static array of entries that each have the
> hex code and string equivalent. Then hv_result_to_string() loops through
> the array looking for a match. This won't be any slower than the big switch
> statement. I've seen other places in the kernel where string names are
> output, and looking up the strings in a static array is the typical approach.
> You'll have to work through the details and see if avoids being too clumsy,
> but I think it will be OK.

I'll try it out, agree the perf difference probably won't be significant or
even matter much.

Thanks
Nuno

> 
> Michael