On 2/20/2025 11:03 AM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> Sent: Thursday, February 20, 2025 10:33 AM
>>
>> Return linux-friendly error codes from hypercall helper functions,
>> which allows them to be used more flexibly.
>>
>> Introduce hv_result_to_errno() for this purpose, which also handles
>> the special value U64_MAX returned from hv_do_hypercall().
>>
>> Signed-off-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/hv/hv_common.c | 34 ++++++++++++++++++++++++++++++++++
>> drivers/hv/hv_proc.c | 6 +++---
>> include/asm-generic/mshyperv.h | 1 +
>> 3 files changed, 38 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
>> index ee3083937b4f..2120aead98d9 100644
>> --- a/drivers/hv/hv_common.c
>> +++ b/drivers/hv/hv_common.c
>> @@ -683,3 +683,37 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
>> return HV_STATUS_INVALID_PARAMETER;
>> }
>> EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
>> +
>> +/* Convert a hypercall result into a linux-friendly error code. */
>> +int hv_result_to_errno(u64 status)
>> +{
>> + /* hv_do_hypercall() may return U64_MAX, hypercalls aren't possible */
>> + if (unlikely(status == U64_MAX))
>> + return -EOPNOTSUPP;
>> + /*
>> + * A failed hypercall is usually only recoverable (or loggable) near
>> + * the call site where the HV_STATUS_* code is known. So the errno
>> + * it gets converted to is not too useful further up the stack.
>> + * Provice a few mappings that could be useful, and revert to -EIO
>> + * as a fallback.
>> + */
>> + switch (hv_result(status)) {
>> + case HV_STATUS_SUCCESS:
>> + return 0;
>> + case HV_STATUS_INVALID_HYPERCALL_CODE:
>> + case HV_STATUS_INVALID_HYPERCALL_INPUT:
>> + case HV_STATUS_INVALID_PARAMETER:
>> + case HV_STATUS_INVALID_PARTITION_ID:
>> + case HV_STATUS_INVALID_VP_INDEX:
>> + case HV_STATUS_INVALID_PORT_ID:
>> + case HV_STATUS_INVALID_CONNECTION_ID:
>> + case HV_STATUS_INVALID_LP_INDEX:
>> + case HV_STATUS_INVALID_REGISTER_VALUE:
>> + return -EINVAL;
>> + case HV_STATUS_INSUFFICIENT_MEMORY:
>> + return -ENOMEM;
>> + default:
>> + break;
>> + }
>> + return -EIO;
>> +}
>> diff --git a/drivers/hv/hv_proc.c b/drivers/hv/hv_proc.c
>> index 3e410489f480..72b09f1cfa3e 100644
>> --- a/drivers/hv/hv_proc.c
>> +++ b/drivers/hv/hv_proc.c
>> @@ -88,7 +88,7 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages)
>> local_irq_restore(flags);
>> if (!hv_result_success(status)) {
>> pr_err("Failed to deposit pages: %lld\n", status);
>> - ret = hv_result(status);
>> + ret = hv_result_to_errno(status);
>> goto err_free_allocations;
>> }
>>
>> @@ -139,7 +139,7 @@ int hv_call_add_logical_proc(int node, u32 lp_index, u32 apic_id)
>> if (!hv_result_success(status)) {
>> pr_err("%s: cpu %u apic ID %u, %lld\n", __func__,
>> lp_index, apic_id, status);
>> - ret = hv_result(status);
>> + ret = hv_result_to_errno(status);
>> }
>> break;
>> }
>> @@ -181,7 +181,7 @@ int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags)
>> if (!hv_result_success(status)) {
>> pr_err("%s: vcpu %u, lp %u, %lld\n", __func__,
>> vp_index, flags, status);
>> - ret = hv_result(status);
>> + ret = hv_result_to_errno(status);
>> }
>> break;
>> }
>
> In hv_call_add_logical_proc() and hv_call_create_vp(), local variable "ret" is
> defined and initialized to HV_STATUS_SUCCESS. Since "ret" now contains an
> errno value instead of a hypercall status, it should be initialized to zero. (Yes,
> HV_STATUS_SUCCESS is defined as 0, but it's now the wrong abstraction.)
>
Great point, I'll post a v3 to fix it.
> With that fixed,
>
> Reviewed-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
>
>> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
>> index 7adc10a4fa3e..3f115e2bcdaa 100644
>> --- a/include/asm-generic/mshyperv.h
>> +++ b/include/asm-generic/mshyperv.h
>> @@ -297,6 +297,7 @@ static inline int cpumask_to_vpset_skip(struct hv_vpset *vpset,
>> return __cpumask_to_vpset(vpset, cpus, func);
>> }
>>
>> +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);
>> bool hv_is_hibernation_supported(void);
>> --
>> 2.34.1
