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Re: [RFC PATCH v2] ppc/spapr: Add support for H_SCM_PERFORMANCE_STATS hc
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From: |
David Gibson |
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Subject: |
Re: [RFC PATCH v2] ppc/spapr: Add support for H_SCM_PERFORMANCE_STATS hcall |
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Date: |
Mon, 17 May 2021 16:24:54 +1000 |
On Sat, May 15, 2021 at 09:21:48AM +0530, Vaibhav Jain wrote:
> Thanks for looking into this patch David
>
> David Gibson <david@gibson.dropbear.id.au> writes:
>
> > 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@linux.ibm.com
> >>
> >> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> >> ---
> >> 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.
> >
> Sure, removed this check in v3.
>
> >> + /* 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.
> >
> MAX_OUTPUT_BUFFER is the size of buffer required to return all unique
> performance-stats and is dependent on the size if array
> 'nvdimm_perf_stats' and not the hard limit of 255. Since presently
> 'nvdimm_perf_stats' only holds two entries right now hence the above
> assignmen is correct.
Sorry, I misread the new definition.
> I understand that MAX_OUTPUT_BUFFER can be perhaps wrongly named hence
> have changed it to MIN_OUTPUT_BUFFER in v3.
> >> + } 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).
> Yes, thanks for suggesting this. I have added a check in
> scm_perf_check_rr_buffer() to check the size-bounds for rr_buffer.
> >
> > 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.
> >
> I still needed to allocate the 'perfstats' header at the beginning of
> h_scm_performance_stats().
I really don't think you need to.
> So instead of allocating 'size' bytes I am
> now allocating 'MAX_OUTPUT_BUFFER' buffer at the beginning thats also
> used to copy the rr-buffer header from guest, which is then populated
> with stats and then copied to guest memory in single shot.
>
> >> + 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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