[PATCH v2 11/11] plugins: new hwprofile plugin

["Alex Bennée" <alex.bennee@linaro.org>]

This is a plugin intended to help with profiling access to various
bits of system hardware. It only really makes sense for system
emulation.

It takes advantage of the recently exposed helper API that allows us
to see the device name (memory region name) associated with a device.

You can specify arg=read or arg=write to limit the tracking to just
reads or writes (by default it does both).

The pattern option:

  -plugin ./tests/plugin/libhwprofile.so,arg=pattern

will allow you to see the access pattern to devices, eg:

  gic_cpu @ 0xffffffc010040000
    off:00000000, 8, 1, 8, 1
    off:00000000, 4, 1, 4, 1
    off:00000000, 2, 1, 2, 1
    off:00000000, 1, 1, 1, 1

The source option:

  -plugin ./tests/plugin/libhwprofile.so,arg=source

will track the virtual source address of the instruction making the
access:

  pl011 @ 0xffffffc010031000
    pc:ffffffc0104c785c, 1, 4, 0, 0
    pc:ffffffc0104c7898, 1, 4, 0, 0
    pc:ffffffc010512bcc, 2, 1867, 0, 0

You cannot mix source and pattern.

Finally the match option allow you to limit the tracking to just the
devices you care about.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
Tested-by: Robert Foley <robert.foley@linaro.org>

---
v2
  - use 64 bit cpu masks
  - warn if we will exceed cpu mask capability
  - don't run in linux-user mode
  - skip in check-tcg for linux-user test
v3
  - update device name API
  - re-factor and clean-up
  - add source tracking
  - use direct hash for source/pattern
  - add match function
  - expand the commit message
  - checkpatch cleanups
---
 tests/plugin/hwprofile.c  | 305 ++++++++++++++++++++++++++++++++++++++
 tests/plugin/Makefile     |   1 +
 tests/tcg/Makefile.target |  12 +-
 3 files changed, 316 insertions(+), 2 deletions(-)
 create mode 100644 tests/plugin/hwprofile.c

diff --git a/tests/plugin/hwprofile.c b/tests/plugin/hwprofile.c
new file mode 100644
index 0000000000..6dac1d5f85
--- /dev/null
+++ b/tests/plugin/hwprofile.c
@@ -0,0 +1,305 @@
+/*
+ * Copyright (C) 2020, Alex Bennée <alex.bennee@linaro.org>
+ *
+ * HW Profile - breakdown access patterns for IO to devices
+ *
+ * License: GNU GPL, version 2 or later.
+ *   See the COPYING file in the top-level directory.
+ */
+
+#include <inttypes.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <glib.h>
+
+#include <qemu-plugin.h>
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+typedef struct {
+    uint64_t cpu_read;
+    uint64_t cpu_write;
+    uint64_t reads;
+    uint64_t writes;
+} IOCounts;
+
+typedef struct {
+    uint64_t off_or_pc;
+    IOCounts counts;
+} IOLocationCounts;
+
+typedef struct {
+    const char *name;
+    uint64_t   base;
+    IOCounts   totals;
+    GHashTable *detail;
+} DeviceCounts;
+
+static GMutex lock;
+static GHashTable *devices;
+
+/* track the access pattern to a piece of HW */
+static bool pattern;
+/* track the source address of access to HW */
+static bool source;
+/* track only matched regions of HW */
+static bool check_match;
+static gchar **matches;
+
+static enum qemu_plugin_mem_rw rw = QEMU_PLUGIN_MEM_RW;
+
+static inline bool track_reads(void)
+{
+    return rw == QEMU_PLUGIN_MEM_RW || rw == QEMU_PLUGIN_MEM_R;
+}
+
+static inline bool track_writes(void)
+{
+    return rw == QEMU_PLUGIN_MEM_RW || rw == QEMU_PLUGIN_MEM_W;
+}
+
+static void plugin_init(void)
+{
+    devices = g_hash_table_new(NULL, NULL);
+}
+
+static gint sort_cmp(gconstpointer a, gconstpointer b)
+{
+    DeviceCounts *ea = (DeviceCounts *) a;
+    DeviceCounts *eb = (DeviceCounts *) b;
+    return ea->totals.reads + ea->totals.writes >
+           eb->totals.reads + eb->totals.writes ? -1 : 1;
+}
+
+static gint sort_loc(gconstpointer a, gconstpointer b)
+{
+    IOLocationCounts *ea = (IOLocationCounts *) a;
+    IOLocationCounts *eb = (IOLocationCounts *) b;
+    return ea->off_or_pc > eb->off_or_pc;
+}
+
+static void fmt_iocount_record(GString *s, IOCounts *rec)
+{
+    if (track_reads()) {
+        g_string_append_printf(s, ", %"PRIx64", %"PRId64,
+                               rec->cpu_read, rec->reads);
+    }
+    if (track_writes()) {
+        g_string_append_printf(s, ", %"PRIx64", %"PRId64,
+                               rec->cpu_write, rec->writes);
+    }
+}
+
+static void fmt_dev_record(GString *s, DeviceCounts *rec)
+{
+    g_string_append_printf(s, "%s, 0x%"PRIx64,
+                           rec->name, rec->base);
+    fmt_iocount_record(s, &rec->totals);
+    g_string_append_c(s, '\n');
+}
+
+static void plugin_exit(qemu_plugin_id_t id, void *p)
+{
+    g_autoptr(GString) report = g_string_new("");
+    GList *counts;
+
+    if (!(pattern || source)) {
+        g_string_printf(report, "Device, Address");
+        if (track_reads()) {
+            g_string_append_printf(report, ", RCPUs, Reads");
+        }
+        if (track_writes()) {
+            g_string_append_printf(report, ",  WCPUs, Writes");
+        }
+        g_string_append_c(report, '\n');
+    }
+
+    counts = g_hash_table_get_values(devices);
+    if (counts && g_list_next(counts)) {
+        GList *it;
+
+        it = g_list_sort(counts, sort_cmp);
+
+        while (it) {
+            DeviceCounts *rec = (DeviceCounts *) it->data;
+            if (rec->detail) {
+                GList *accesses = g_hash_table_get_values(rec->detail);
+                GList *io_it = g_list_sort(accesses, sort_loc);
+                const char *prefix = pattern ? "off" : "pc";
+                g_string_append_printf(report, "%s @ 0x%"PRIx64"\n",
+                                       rec->name, rec->base);
+                while (io_it) {
+                    IOLocationCounts *loc = (IOLocationCounts *) io_it->data;
+                    g_string_append_printf(report, "  %s:%08"PRIx64,
+                                           prefix, loc->off_or_pc);
+                    fmt_iocount_record(report, &loc->counts);
+                    g_string_append_c(report, '\n');
+                    io_it = io_it->next;
+                }
+            } else {
+                fmt_dev_record(report, rec);
+            }
+            it = it->next;
+        };
+        g_list_free(it);
+    }
+
+    qemu_plugin_outs(report->str);
+}
+
+static DeviceCounts *new_count(const char *name, uint64_t base)
+{
+    DeviceCounts *count = g_new0(DeviceCounts, 1);
+    count->name = name;
+    count->base = base;
+    if (pattern || source) {
+        count->detail = g_hash_table_new(NULL, NULL);
+    }
+    g_hash_table_insert(devices, (gpointer) name, count);
+    return count;
+}
+
+static IOLocationCounts *new_location(GHashTable *table, uint64_t off_or_pc)
+{
+    IOLocationCounts *loc = g_new0(IOLocationCounts, 1);
+    loc->off_or_pc = off_or_pc;
+    g_hash_table_insert(table, (gpointer) off_or_pc, loc);
+    return loc;
+}
+
+static void hwprofile_match_hit(DeviceCounts *rec, uint64_t off)
+{
+    g_autoptr(GString) report = g_string_new("hwprofile: match @ offset");
+    g_string_append_printf(report, "%"PRIx64", previous hits\n", off);
+    fmt_dev_record(report, rec);
+    qemu_plugin_outs(report->str);
+}
+
+static void inc_count(IOCounts *count, bool is_write, unsigned int cpu_index)
+{
+    if (is_write) {
+        count->writes++;
+        count->cpu_write |= (1 << cpu_index);
+    } else {
+        count->reads++;
+        count->cpu_read |= (1 << cpu_index);
+    }
+}
+
+static void vcpu_haddr(unsigned int cpu_index, qemu_plugin_meminfo_t meminfo,
+                       uint64_t vaddr, void *udata)
+{
+    struct qemu_plugin_hwaddr *hwaddr = qemu_plugin_get_hwaddr(meminfo, vaddr);
+
+    if (!hwaddr || !qemu_plugin_hwaddr_is_io(hwaddr)) {
+        return;
+    } else {
+        const char *name = qemu_plugin_hwaddr_device_name(hwaddr);
+        uint64_t off = qemu_plugin_hwaddr_device_offset(hwaddr);
+        bool is_write = qemu_plugin_mem_is_store(meminfo);
+        DeviceCounts *counts;
+
+        g_mutex_lock(&lock);
+        counts = (DeviceCounts *) g_hash_table_lookup(devices, name);
+
+        if (!counts) {
+            uint64_t base = vaddr - off;
+            counts = new_count(name, base);
+        }
+
+        if (check_match) {
+            if (g_strv_contains((const char * const *)matches, counts->name)) {
+                hwprofile_match_hit(counts, off);
+                inc_count(&counts->totals, is_write, cpu_index);
+            }
+        } else {
+            inc_count(&counts->totals, is_write, cpu_index);
+        }
+
+        /* either track offsets or source of access */
+        if (source) {
+            off = (uint64_t) udata;
+        }
+
+        if (pattern || source) {
+            IOLocationCounts *io_count = g_hash_table_lookup(counts->detail,
+                                                             (gpointer) off);
+            if (!io_count) {
+                io_count = new_location(counts->detail, off);
+            }
+            inc_count(&io_count->counts, is_write, cpu_index);
+        }
+
+        g_mutex_unlock(&lock);
+    }
+}
+
+static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
+{
+    size_t n = qemu_plugin_tb_n_insns(tb);
+    size_t i;
+
+    for (i = 0; i < n; i++) {
+        struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
+        gpointer udata = (gpointer) (source ? qemu_plugin_insn_vaddr(insn) : 0);
+        qemu_plugin_register_vcpu_mem_cb(insn, vcpu_haddr,
+                                         QEMU_PLUGIN_CB_NO_REGS,
+                                         rw, udata);
+    }
+}
+
+QEMU_PLUGIN_EXPORT
+int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
+                        int argc, char **argv)
+{
+    int i;
+
+    for (i = 0; i < argc; i++) {
+        char *opt = argv[i];
+        if (g_strcmp0(opt, "read") == 0) {
+            rw = QEMU_PLUGIN_MEM_R;
+        } else if (g_strcmp0(opt, "write") == 0) {
+            rw = QEMU_PLUGIN_MEM_W;
+        } else if (g_strcmp0(opt, "pattern") == 0) {
+            pattern = true;
+        } else if (g_strcmp0(opt, "source") == 0) {
+            source = true;
+        } else if (g_str_has_prefix(opt, "match")) {
+            gchar **parts = g_strsplit(opt, "=", 2);
+            check_match = true;
+            matches = g_strsplit(parts[1], ",", -1);
+            g_strfreev(parts);
+        } else {
+            fprintf(stderr, "option parsing failed: %s\n", opt);
+            return -1;
+        }
+    }
+
+    if (source && pattern) {
+        fprintf(stderr, "can only currently track either source or pattern.\n");
+        return -1;
+    }
+
+    if (!info->system_emulation) {
+        fprintf(stderr, "hwprofile: plugin only useful for system emulation\n");
+        return -1;
+    }
+
+    /* Just warn about overflow */
+    if (info->system.smp_vcpus > 64 ||
+        info->system.max_vcpus > 64) {
+        fprintf(stderr, "hwprofile: can only track up to 64 CPUs\n");
+    }
+
+    plugin_init();
+
+    qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
+    qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
+    return 0;
+}
diff --git a/tests/plugin/Makefile b/tests/plugin/Makefile
index e9348fde4a..e9d1947751 100644
--- a/tests/plugin/Makefile
+++ b/tests/plugin/Makefile
@@ -21,6 +21,7 @@ NAMES += hotblocks
 NAMES += howvec
 NAMES += hotpages
 NAMES += lockstep
+NAMES += hwprofile
 
 SONAMES := $(addsuffix .so,$(addprefix lib,$(NAMES)))
 
diff --git a/tests/tcg/Makefile.target b/tests/tcg/Makefile.target
index 4b2b696fce..bc595b0588 100644
--- a/tests/tcg/Makefile.target
+++ b/tests/tcg/Makefile.target
@@ -129,8 +129,16 @@ ifeq ($(CONFIG_PLUGIN),y)
 PLUGIN_SRC=$(SRC_PATH)/tests/plugin
 PLUGIN_LIB=../../plugin
 VPATH+=$(PLUGIN_LIB)
-PLUGINS=$(filter-out liblockstep.so,\
-		$(patsubst %.c, lib%.so, $(notdir $(wildcard $(PLUGIN_SRC)/*.c))))
+
+# Some plugins aren't testable automatically
+SKIP_PLUGINS=liblockstep.so
+ifdef CONFIG_USER_ONLY
+SKIP_PLUGINS+=libhwprofile.so
+endif
+
+PLUGINS=$(filter-out $(SKIP_PLUGINS),\
+		$(patsubst %.c, lib%.so, \
+			$(notdir $(wildcard $(PLUGIN_SRC)/*.c))))
 
 # We need to ensure expand the run-plugin-TEST-with-PLUGIN
 # pre-requistes manually here as we can't use stems to handle it. We
-- 
2.20.1