[PATCH v2 1/3] hyperv: Convert hypercall statuses to linux error codes

[Nuno Das Neves]

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 at linux.microsoft.com>
---
 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;
 		}
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