On Thu, May 06, 2021 at 08:19:24AM +0530, Vaibhav Jain wrote:
> Add support for H_SCM_PERFORMANCE_STATS described at [1] for
> spapr nvdimms. This enables guest to fetch performance stats[2] like
> expected life of an nvdimm ('MemLife ') etc and display them to the
> user. Linux kernel support for fetching these performance stats and
> exposing them to the user-space was done via [3].
>
> The hcall semantics mandate that each nvdimm performance stats is
> uniquely identied by a 8-byte ascii string encoded as an unsigned
> integer (e.g 'MemLife ' == 0x4D656D4C69666520) and its value be a
> 8-byte unsigned integer. These performance-stats are exchanged with
> the guest in via a guest allocated buffer called
> 'requestAndResultBuffer' or rr-buffer for short. This buffer contains
> a header descibed by 'struct papr_scm_perf_stats' followed by an array
> of performance-stats described by 'struct papr_scm_perf_stat'. The
> hypervisor is expected to validate the rr-buffer header and then based
> on the request copy the needed performance-stats to the array of
> 'struct papr_scm_perf_stat' following the header.
>
> The patch proposes a new function h_scm_performance_stats() that
> services the H_SCM_PERFORMANCE_STATS hcall. After verifying the
> validity of the rr-buffer header via scm_perf_check_rr_buffer() it
> proceeds to fill the rr-buffer with requested performance-stats. The
> value of individual stats is retrived from individual accessor
> function for the stat which are indexed in the array
> 'nvdimm_perf_stats'.
>
> References:
> [1] "Hypercall Op-codes (hcalls)"
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst#n269
> [2] Sysfs attribute documentation for papr_scm
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/testing/sysfs-bus-papr-pmem#n36
> [3] "powerpc/papr_scm: Fetch nvdimm performance stats from PHYP"
> https://lore.kernel.org/r/20200731064153.182203-2-vaibhav@xxxxxxxxxxxxx
>
> Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
> ---
> Changelog
>
> RFC-v1:
> * Removed empty lines from code [ David ]
> * Updated struct papr_scm_perf_stat to use uint64_t for
> statistic_id.
> * Added a hard limit on max number of stats requested to 255 [ David ]
> * Updated scm_perf_check_rr_buffer() to check for rr-buffer header
> size [ David ]
> * Removed a redundant check from nvdimm_stat_getval() [ David ]
> * Removed a redundant call to address_space_access_valid() in
> scm_perf_check_rr_buffer() [ David ]
> * Instead of allocating a minimum size local buffer, allocate a max
> possible size local rr-buffer. [ David ]
> * Updated nvdimm_stat_getval() to set 'val' to '0' on error. [ David ]
> * Updated h_scm_performance_stats() to use a canned-response method
> for simplifying num_stats==0 case [ David ].
> ---
> hw/ppc/spapr_nvdimm.c | 230 +++++++++++++++++++++++++++++++++++++++++
> include/hw/ppc/spapr.h | 19 +++-
> 2 files changed, 248 insertions(+), 1 deletion(-)
>
> diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
> index 252204e25f..b0c2b55a5b 100644
> --- a/hw/ppc/spapr_nvdimm.c
> +++ b/hw/ppc/spapr_nvdimm.c
> @@ -35,6 +35,14 @@
> /* SCM device is unable to persist memory contents */
> #define PAPR_PMEM_UNARMED PPC_BIT(0)
>
> +/* Maximum output buffer size needed to return all nvdimm_perf_stats */
> +#define SCM_STATS_MAX_OUTPUT_BUFFER (sizeof(struct papr_scm_perf_stats) + \
> + sizeof(struct papr_scm_perf_stat) * \
> + ARRAY_SIZE(nvdimm_perf_stats))
> +
> +/* Maximum number of stats that we can return back in a single stat request */
> +#define SCM_STATS_MAX_STATS 255
> +
> bool spapr_nvdimm_validate(HotplugHandler *hotplug_dev, NVDIMMDevice *nvdimm,
> uint64_t size, Error **errp)
> {
> @@ -502,6 +510,227 @@ static target_ulong h_scm_health(PowerPCCPU *cpu, SpaprMachineState *spapr,
> return H_SUCCESS;
> }
>
> +static int perf_stat_noop(SpaprDrc *drc, uint64_t unused, uint64_t *val)
> +{
> + *val = 0;
> + return H_SUCCESS;
> +}
> +
> +static int perf_stat_memlife(SpaprDrc *drc, uint64_t unused, uint64_t *val)
> +{
> + /* Assume full life available of an NVDIMM right now */
> + *val = 100;
> + return H_SUCCESS;
> +}
> +
> +/*
> + * Holds all supported performance stats accessors. Each performance-statistic
> + * is uniquely identified by a 8-byte ascii string for example: 'MemLife '
> + * which indicate in percentage how much usage life of an nvdimm is remaining.
> + * 'NoopStat' which is primarily used to test support for retriving performance
> + * stats and also to replace unknown stats present in the rr-buffer.
> + *
> + */
> +static const struct {
> + char stat_id[8];
> + int (*stat_getval)(SpaprDrc *drc, uint64_t id, uint64_t *val);
> +} nvdimm_perf_stats[] = {
> + { "NoopStat", perf_stat_noop},
> + { "MemLife ", perf_stat_memlife},
> +};
> +
> +/*
> + * Given a nvdimm drc and stat-name return its value. In case given stat-name
> + * isnt supported then return H_PARTIAL.
> + */
> +static int nvdimm_stat_getval(SpaprDrc *drc, uint64_t id, uint64_t *val)
> +{
> + int index;
> + char stat_id[8];
> +
> + /* since comparision is done */
> + memcpy(&stat_id[0], &id, 8);
> + *val = 0;
> +
> + /* Lookup the stats-id in the nvdimm_perf_stats table */
> + for (index = 0; index < ARRAY_SIZE(nvdimm_perf_stats); ++index) {
> + if (memcmp(nvdimm_perf_stats[index].stat_id, &stat_id[0], 8) == 0) {
> + return nvdimm_perf_stats[index].stat_getval(drc, id, val);
> + }
> + }
> + return H_PARTIAL;
> +}
> +
> +/*
> + * Given a request & result buffer header verify its contents. Also
> + * verify that buffer & buffer-size provided by the guest is accessible and
> + * large enough to hold the requested stats. The size of buffer needed to
> + * hold the requested 'num_stat' number of stats is returned in 'size'.
> + */
> +static int scm_perf_check_rr_buffer(struct papr_scm_perf_stats *header,
> + hwaddr addr, size_t *size,
> + uint32_t *num_stats)
> +{
> + size_t expected_buffsize;
> +
> + /* verify size is enough to hold rr-buffer header */
> + if (*size < sizeof(struct papr_scm_perf_stats)) {
> + return H_BAD_DATA;
> + }
You have already checked this in the caller, so strictly speaking you
don't need to do so again.
> + /* Verify the header eyecather and version */
> + if (memcmp(&header->eye_catcher, SCM_STATS_EYECATCHER,
> + sizeof(header->eye_catcher))) {
> + return H_BAD_DATA;
> + }
> + if (be32_to_cpu(header->stats_version) != 0x1) {
> + return H_NOT_AVAILABLE;
> + }
> +
> + /* verify that rr buffer has enough space */
> + *num_stats = be32_to_cpu(header->num_statistics);
> + if (*num_stats == 0) { /* Return all stats */
> + expected_buffsize = SCM_STATS_MAX_OUTPUT_BUFFER;
I don't think this is right. MAX_OUTPUT_BUFFER is based on 255 stats
being returned, but num_stats==0 only returns 2 at present.
> + } else if (*num_stats > SCM_STATS_MAX_STATS) {
> + /* Too many stats requested */
> + return H_P3;
> + } else { /* Return a subset of stats */
> + expected_buffsize = sizeof(struct papr_scm_perf_stats) +
> + (*num_stats) * sizeof(struct papr_scm_perf_stat);
> + }
> +
> + if (*size < expected_buffsize) {
> + return H_P3;
> + }
> + *size = expected_buffsize;
> +
> + return H_SUCCESS;
> +}
> +
> +/*
> + * For a given DRC index (R3) return one ore more performance stats of an nvdimm
> + * device in guest allocated Request-and-result buffer (rr-buffer) (R4) of
> + * given 'size' (R5). The rr-buffer consists of a header described by
> + * 'struct papr_scm_perf_stats' that embeds the 'stats_version' and
> + * 'num_statistics' fields. This is followed by an array of
> + * 'struct papr_scm_perf_stat'. Based on the request type the writes the
> + * performance into the array of 'struct papr_scm_perf_stat' embedded inside
> + * the rr-buffer provided by the guest.
> + * Special cases handled are:
> + * 'size' == 0 : Return the maximum possible size of rr-buffer
> + * 'size' != 0 && 'num_statistics == 0' : Return all possible performance stats
> + *
> + * In case there was an error fetching a specific stats (e.g stat-id unknown or
> + * any other error) then return the stat-id in R4 and also replace its stat
> + * entry in rr-buffer with 'NoopStat'
> + */
> +static target_ulong h_scm_performance_stats(PowerPCCPU *cpu,
> + SpaprMachineState *spapr,
> + target_ulong opcode,
> + target_ulong *args)
> +{
> + SpaprDrc *drc = spapr_drc_by_index(args[0]);
> + const hwaddr addr = args[1];
> + size_t size = args[2];
> + struct papr_scm_perf_stats perfstats;
> + struct papr_scm_perf_stat *stats;
> + uint64_t invalid_stat = 0, stat_val;
> + MemTxResult result;
> + uint32_t num_stats;
> + unsigned long rc;
> + int index;
> +
> + /* Ensure that the drc is valid & is valid PMEM dimm and is plugged in */
> + if (!drc || !drc->dev ||
> + spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
> + return H_PARAMETER;
> + }
> +
> + /* Guest requested max buffer size for output buffer */
> + if (size == 0) {
> + args[0] = SCM_STATS_MAX_OUTPUT_BUFFER;
> + return H_SUCCESS;
> + }
> +
> + /* verify size is enough to hold rr-buffer header */
> + if (size < sizeof(struct papr_scm_perf_stats)) {
> + return H_BAD_DATA;
> + }
> +
> + /* Read and verify rr-buffer header */
> + result = address_space_read(&address_space_memory, addr,
> + MEMTXATTRS_UNSPECIFIED, &perfstats,
> + sizeof(perfstats));
> + if (result != MEMTX_OK) {
> + return H_PRIVILEGE;
> + }
> +
> + /* Verify that the rr-buffer is valid */
> + rc = scm_perf_check_rr_buffer(&perfstats, addr, &size, &num_stats);
> + if (rc != H_SUCCESS) {
> + return rc;
> + }
> +
> + /* allocate enough buffer space locally for holding max stats */
> + stats = g_try_malloc0(SCM_STATS_MAX_STATS *
> + sizeof(struct papr_scm_perf_stat));
I think you can simplify the allocation and mem read/write logic even
further. You're given the expected buffer size in a register. So you
can fail out early if that value is too large (> MAX_OUTPUT_BUFFER) or
too small (< header size).
Then you can make a single allocation of (size) bytes and copy in both
the header and the body as one unit. Validate and fill it, then write
it back as a single unit as well.
> + if (!stats) {
> + return H_NO_MEM;
> + }
> +
> + /* when returning all stats generate a canned response first */
> + if (num_stats == 0) {
> + for (index = 1; index < ARRAY_SIZE(nvdimm_perf_stats); ++index) {
> + memcpy(&stats[index - 1].statistic_id,
> + &nvdimm_perf_stats[index].stat_id, 8);
> + }
> + num_stats = ARRAY_SIZE(nvdimm_perf_stats) - 1;
> + } else {
> + /* copy the rr-buffer from the guest memory */
> + result = address_space_read(&address_space_memory,
> + addr + sizeof(struct papr_scm_perf_stats),
> + MEMTXATTRS_UNSPECIFIED, stats,
> + size - sizeof(struct papr_scm_perf_stats));
> + if (result != MEMTX_OK) {
> + g_free(stats);
> + return H_PRIVILEGE;
> + }
> + }
> +
> + for (index = 0; index < num_stats; ++index) {
> + rc = nvdimm_stat_getval(drc, stats[index].statistic_id, &stat_val);
> +
> + /* On error add noop stat to rr buffer & save last inval stat-id */
> + if (rc != H_SUCCESS) {
> + if (!invalid_stat) {
> + invalid_stat = stats[index].statistic_id;
> + }
> + memcpy(&stats[index].statistic_id, nvdimm_perf_stats[0].stat_id, 8);
> + }
> + /* Caller expects stat values in BE encoding */
> + stats[index].statistic_value = cpu_to_be64(stat_val);
> + }
> +
> + /* Update and copy the local rr-buffer header and stats back to guest */
> + perfstats.num_statistics = cpu_to_be32(num_stats);
> + result = address_space_write(&address_space_memory, addr,
> + MEMTXATTRS_UNSPECIFIED, &perfstats,
> + sizeof(struct papr_scm_perf_stats));
> + if (result == MEMTX_OK) {
> + result = address_space_write(&address_space_memory,
> + addr + sizeof(struct papr_scm_perf_stats),
> + MEMTXATTRS_UNSPECIFIED, stats,
> + size - sizeof(struct papr_scm_perf_stats));
> + }
> + /* Cleanup the stats buffer */
> + g_free(stats);
> + if (result) {
> + return H_PRIVILEGE;
> + }
> + /* Check if there was a failure in fetching any stat */
> + args[0] = invalid_stat;
> + return invalid_stat ? H_PARTIAL : H_SUCCESS;
> +}
> +
> static void spapr_scm_register_types(void)
> {
> /* qemu/scm specific hcalls */
> @@ -511,6 +740,7 @@ static void spapr_scm_register_types(void)
> spapr_register_hypercall(H_SCM_UNBIND_MEM, h_scm_unbind_mem);
> spapr_register_hypercall(H_SCM_UNBIND_ALL, h_scm_unbind_all);
> spapr_register_hypercall(H_SCM_HEALTH, h_scm_health);
> + spapr_register_hypercall(H_SCM_PERFORMANCE_STATS, h_scm_performance_stats);
> }
>
> type_init(spapr_scm_register_types)
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index d2b5a9bdf9..6f3353b4ea 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -326,6 +326,7 @@ struct SpaprMachineState {
> #define H_P8 -61
> #define H_P9 -62
> #define H_OVERLAP -68
> +#define H_BAD_DATA -70
> #define H_UNSUPPORTED_FLAG -256
> #define H_MULTI_THREADS_ACTIVE -9005
>
> @@ -539,8 +540,9 @@ struct SpaprMachineState {
> #define H_SCM_UNBIND_MEM 0x3F0
> #define H_SCM_UNBIND_ALL 0x3FC
> #define H_SCM_HEALTH 0x400
> +#define H_SCM_PERFORMANCE_STATS 0x418
>
> -#define MAX_HCALL_OPCODE H_SCM_HEALTH
> +#define MAX_HCALL_OPCODE H_SCM_PERFORMANCE_STATS
>
> /* The hcalls above are standardized in PAPR and implemented by pHyp
> * as well.
> @@ -787,6 +789,21 @@ OBJECT_DECLARE_SIMPLE_TYPE(SpaprTceTable, SPAPR_TCE_TABLE)
> DECLARE_INSTANCE_CHECKER(IOMMUMemoryRegion, SPAPR_IOMMU_MEMORY_REGION,
> TYPE_SPAPR_IOMMU_MEMORY_REGION)
>
> +/* Defs and structs exchanged with guest when reporting drc perf stats */
> +#define SCM_STATS_EYECATCHER "SCMSTATS"
> +
> +struct QEMU_PACKED papr_scm_perf_stat {
> + uint64_t statistic_id;
> + uint64_t statistic_value;
> +};
> +
> +struct QEMU_PACKED papr_scm_perf_stats {
> + uint8_t eye_catcher[8]; /* Should be “SCMSTATS” */
> + uint32_t stats_version; /* Should be 0x01 */
> + uint32_t num_statistics; /* Number of stats following */
> + struct papr_scm_perf_stat scm_statistics[]; /* Performance matrics */
> +};
> +
> struct SpaprTceTable {
> DeviceState parent;
> uint32_t liobn;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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