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Message-ID:
<SN6PR02MB4157E630EC520DC487139372D4DE2@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Tue, 18 Mar 2025 18:01:36 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>, "linux-arm-kernel@...ts.infradead.org"
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<linux-kernel@...r.kernel.org>, "linux-arch@...r.kernel.org"
<linux-arch@...r.kernel.org>, "ltykernel@...il.com" <ltykernel@...il.com>,
"stanislav.kinsburskiy@...il.com" <stanislav.kinsburskiy@...il.com>,
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Subject: RE: [PATCH v6 01/10] hyperv: Log hypercall status codes as strings
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Friday, March 14, 2025 12:29 PM
>
> Introduce hv_status_printk() macros as a convenience to log hypercall
> errors, formatting them with the status code (HV_STATUS_*) as a raw hex
> value and also as a string, which saves some time while debugging.
>
> Create a table of HV_STATUS_ codes with strings and mapped errnos, and
> use it for hv_result_to_string() and hv_result_to_errno().
>
> Use the new hv_status_printk()s in hv_proc.c, hyperv-iommu.c, and
> irqdomain.c hypercalls to aid debugging in the root partition.
>
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> Reviewed-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
> ---
> arch/x86/hyperv/irqdomain.c | 6 +-
> drivers/hv/hv_common.c | 129 ++++++++++++++++++++++++---------
> drivers/hv/hv_proc.c | 10 +--
> drivers/iommu/hyperv-iommu.c | 4 +-
> include/asm-generic/mshyperv.h | 13 ++++
> 5 files changed, 118 insertions(+), 44 deletions(-)
>
[snip]
> +
> +struct hv_status_info {
> + char *string;
> + int errno;
> + u16 code;
> +};
> +
> +/*
> + * Note on the errno mappings:
> + * 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.
> + * Provide a few mappings that could be useful, and revert to -EIO
> + * as a fallback.
> + */
> +static const struct hv_status_info hv_status_infos[] = {
> +#define _STATUS_INFO(status, errno) { #status, (errno), (status) }
> + _STATUS_INFO(HV_STATUS_SUCCESS, 0),
> + _STATUS_INFO(HV_STATUS_INVALID_HYPERCALL_CODE, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INVALID_HYPERCALL_INPUT, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INVALID_ALIGNMENT, -EIO),
> + _STATUS_INFO(HV_STATUS_INVALID_PARAMETER, -EINVAL),
> + _STATUS_INFO(HV_STATUS_ACCESS_DENIED, -EIO),
> + _STATUS_INFO(HV_STATUS_INVALID_PARTITION_STATE, -EIO),
> + _STATUS_INFO(HV_STATUS_OPERATION_DENIED, -EIO),
> + _STATUS_INFO(HV_STATUS_UNKNOWN_PROPERTY, -EIO),
> + _STATUS_INFO(HV_STATUS_PROPERTY_VALUE_OUT_OF_RANGE, -EIO),
> + _STATUS_INFO(HV_STATUS_INSUFFICIENT_MEMORY, -ENOMEM),
> + _STATUS_INFO(HV_STATUS_INVALID_PARTITION_ID, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INVALID_VP_INDEX, -EINVAL),
> + _STATUS_INFO(HV_STATUS_NOT_FOUND, -EIO),
> + _STATUS_INFO(HV_STATUS_INVALID_PORT_ID, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INVALID_CONNECTION_ID, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INSUFFICIENT_BUFFERS, -EIO),
> + _STATUS_INFO(HV_STATUS_NOT_ACKNOWLEDGED, -EIO),
> + _STATUS_INFO(HV_STATUS_INVALID_VP_STATE, -EIO),
> + _STATUS_INFO(HV_STATUS_NO_RESOURCES, -EIO),
> + _STATUS_INFO(HV_STATUS_PROCESSOR_FEATURE_NOT_SUPPORTED, -EIO),
> + _STATUS_INFO(HV_STATUS_INVALID_LP_INDEX, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INVALID_REGISTER_VALUE, -EINVAL),
> + _STATUS_INFO(HV_STATUS_INVALID_LP_INDEX, -EIO),
> + _STATUS_INFO(HV_STATUS_INVALID_REGISTER_VALUE, -EIO),
> + _STATUS_INFO(HV_STATUS_OPERATION_FAILED, -EIO),
> + _STATUS_INFO(HV_STATUS_TIME_OUT, -EIO),
> + _STATUS_INFO(HV_STATUS_CALL_PENDING, -EIO),
> + _STATUS_INFO(HV_STATUS_VTL_ALREADY_ENABLED, -EIO),
> +#undef _STATUS_INFO
> +};
> +
> +static inline const struct hv_status_info *find_hv_status_info(u64 hv_status)
> +{
> + int i;
> + u16 code = hv_result(hv_status);
> +
> + for (i = 0; i < ARRAY_SIZE(hv_status_infos); ++i) {
> + const struct hv_status_info *info = &hv_status_infos[i];
> +
> + if (info->code == code)
> + return info;
> + }
> +
> + return NULL;
> +}
> +
> +/* Convert a hypercall result into a linux-friendly error code. */
> +int hv_result_to_errno(u64 status)
> +{
> + const struct hv_status_info *info;
> +
> + /* hv_do_hypercall() may return U64_MAX, hypercalls aren't possible */
> + if (unlikely(status == U64_MAX))
> + return -EOPNOTSUPP;
> +
> + info = find_hv_status_info(status);
> + if (info)
> + return info->errno;
> +
> + return -EIO;
> +}
> +EXPORT_SYMBOL_GPL(hv_result_to_errno);
> +
> +const char *hv_result_to_string(u64 status)
> +{
> + const struct hv_status_info *info;
> +
> + if (unlikely(status == U64_MAX))
> + return "Hypercall page missing!";
> +
> + info = find_hv_status_info(status);
> + if (info)
> + return info->string;
> +
> + return "Unknown";
> +}
> +EXPORT_SYMBOL_GPL(hv_result_to_string);
I think the table-driven approach worked out pretty well. But here's a version that
is even more compact, and avoids the duplicate testing for U64_MAX and having
to special case both U64_MAX and not finding a match:
+
+struct hv_status_info {
+ char *string;
+ int errno;
+ int code;
+};
+
+/*
+ * Note on the errno mappings:
+ * 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.
+ * Provide a few mappings that could be useful, and revert to -EIO
+ * as a fallback.
+ */
+static const struct hv_status_info hv_status_infos[] = {
+#define _STATUS_INFO(status, errno) { #status, (errno), (status) }
+ _STATUS_INFO(HV_STATUS_SUCCESS, 0),
+ _STATUS_INFO(HV_STATUS_INVALID_HYPERCALL_CODE, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INVALID_HYPERCALL_INPUT, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INVALID_ALIGNMENT, -EIO),
+ _STATUS_INFO(HV_STATUS_INVALID_PARAMETER, -EINVAL),
+ _STATUS_INFO(HV_STATUS_ACCESS_DENIED, -EIO),
+ _STATUS_INFO(HV_STATUS_INVALID_PARTITION_STATE, -EIO),
+ _STATUS_INFO(HV_STATUS_OPERATION_DENIED, -EIO),
+ _STATUS_INFO(HV_STATUS_UNKNOWN_PROPERTY, -EIO),
+ _STATUS_INFO(HV_STATUS_PROPERTY_VALUE_OUT_OF_RANGE, -EIO),
+ _STATUS_INFO(HV_STATUS_INSUFFICIENT_MEMORY, -ENOMEM),
+ _STATUS_INFO(HV_STATUS_INVALID_PARTITION_ID, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INVALID_VP_INDEX, -EINVAL),
+ _STATUS_INFO(HV_STATUS_NOT_FOUND, -EIO),
+ _STATUS_INFO(HV_STATUS_INVALID_PORT_ID, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INVALID_CONNECTION_ID, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INSUFFICIENT_BUFFERS, -EIO),
+ _STATUS_INFO(HV_STATUS_NOT_ACKNOWLEDGED, -EIO),
+ _STATUS_INFO(HV_STATUS_INVALID_VP_STATE, -EIO),
+ _STATUS_INFO(HV_STATUS_NO_RESOURCES, -EIO),
+ _STATUS_INFO(HV_STATUS_PROCESSOR_FEATURE_NOT_SUPPORTED, -EIO),
+ _STATUS_INFO(HV_STATUS_INVALID_LP_INDEX, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INVALID_REGISTER_VALUE, -EINVAL),
+ _STATUS_INFO(HV_STATUS_INVALID_LP_INDEX, -EIO),
+ _STATUS_INFO(HV_STATUS_INVALID_REGISTER_VALUE, -EIO),
+ _STATUS_INFO(HV_STATUS_OPERATION_FAILED, -EIO),
+ _STATUS_INFO(HV_STATUS_TIME_OUT, -EIO),
+ _STATUS_INFO(HV_STATUS_CALL_PENDING, -EIO),
+ _STATUS_INFO(HV_STATUS_VTL_ALREADY_ENABLED, -EIO),
+ {"Hypercall page missing!", -EOPNOTSUPP, -1}, /* code -1 is "no hypercall page" */
+ {"Unknown", -EIO, -2}, /* code -2 is "Not found" entry; must be last */
+#undef _STATUS_INFO
+};
+
+static inline const struct hv_status_info *find_hv_status_info(u64 hv_status)
+{
+ int i, code;
+ const struct hv_status_info *info;
+
+ /* hv_do_hypercall() may return U64_MAX, hypercalls aren't possible */
+ if (unlikely(hv_status == U64_MAX))
+ code = -1;
+ else
+ code = hv_result(hv_status);
+
+ for (i = 0; i < ARRAY_SIZE(hv_status_infos); ++i) {
+ info = &hv_status_infos[i];
+ if (info->code == code || info->code == -2)
+ break;
+ }
+
+ return info;
+}
+
+/* Convert a hypercall result into a linux-friendly error code. */
+int hv_result_to_errno(u64 status)
+{
+ return find_hv_status_info(status)->errno;
+}
+EXPORT_SYMBOL_GPL(hv_result_to_errno);
+
+const char *hv_result_to_string(u64 status)
+{
+ return find_hv_status_info(status)->string;
+}
+EXPORT_SYMBOL_GPL(hv_result_to_string);
It could be even more compact by exporting find_hv_status_info() and
letting hv_result_to_errno() and hv_result_to_string() be #defines to
find_hv_status_info()->errno and find_hv_status_info()->string,
respectively.
Note that in struct hv_status_info, the "code" field is defined as "int"
instead of "u16" so that it can contain sentinel values -1 and -2 that
won't overlap with HV_STATUS_* values.
Anyway, just a suggestion. The current code works from what I can
see.
Michael
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