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Message-ID:
<SN6PR02MB4157FFDC234AF8E07CDB8A6AD4A72@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Tue, 25 Mar 2025 18:02:03 +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>,
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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 21, 2025 12:13 PM
>
> On 3/18/2025 11:01 AM, Michael Kelley wrote:
> > 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.
> >
> Played around with this some more.
>
> I like your idea of making it more compact by dealing with U64_MAX and
> unknown in find_hv_status_info(), however I'm not as keen on putting
> these cases in the array and iterating over the whole array when they
> could just be static constants or inline struct initializers. See below.
>
> I also like the idea of making hv_result_to_*() functions into simple
> macros and exporting find_hv_status_info(). However, if it gets used
> elsewhere it makes more sense if the returned hv_status_info for the
> "Unknown" case contains the actual status code instead of replacing
> that information with -2, so then I'd want to return it by value
> instead of pointer:
OK, yes I agree that having the -2 in the status code field could
be a little weird.
>
> +static const struct hv_status_info hv_status_infos[] = {
> +#define _STATUS_INFO(status, errno) { #status, (status), (errno) }
> + _STATUS_INFO(HV_STATUS_SUCCESS, 0),
> <snip>
> + _STATUS_INFO(HV_STATUS_VTL_ALREADY_ENABLED, -EIO),
> +#undef _STATUS_INFO
> +};
> +
> +struct hv_status_info hv_get_status_info(u64 hv_status)
> +{
> + int i;
> + const struct hv_status_info *info;
> + u16 code = hv_result(hv_status);
> + struct hv_status_info ret = {"Unknown", code, -EIO};
> +
> + if (hv_status == U64_MAX)
> + ret = (struct hv_status_info){"Hypercall page missing!", -1,
> + -EOPNOTSUPP};
> + else
> + for (i = 0; i < ARRAY_SIZE(hv_status_infos); ++i) {
> + info = &hv_status_infos[i];
> + if (info->code == code) {
> + ret = *info;
> + break;
> + }
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(hv_get_status_info);
>
> and in mshyperv.h:
>
> +#define hv_result_to_string(hv_status) hv_get_status_info(hv_status).string
> +#define hv_result_to_errno(hv_status) hv_get_status_info(hv_status).errno
> +
> +struct hv_status_info {
> + char *string;
> + int code;
> + int errno;
> +};
> +
> +struct hv_status_info hv_get_status_info(u64 hv_status);
>
> Note also I switched the order of code and errno in hv_status_info,
> mainly because I think the struct initializers for "Unknown" and
> "Hypercall page missing!" are more readable with that order:
> {string, code, errno}
>
> Do you see any problems with the above?
I don't see any problems. Having struct hv_status_info assigned
and returned by value is a little out-of-the-ordinary since it is
bigger than 64 bits. But it is only 128 bits so should be OK.
If you want to adopt your new version as a replacement for the
original version, I'm good with that.
Michael
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