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

Michael Kelley
2025-03-06T17:57:49Z

From: Nuno Das Neves <nunodasneves@linux.microsoft.com> 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@linux.microsoft.com>
> ---
> 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.

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.

Michael