[RFC PATCH v2 2/2] tools/misc: Add xen-vcpus-stats tool

[Matias Ezequiel Vara Larsen <matiasevara@xxxxxxxxx>]

Add a demonstration tool that uses the stats_table resource to
query vcpus' RUNSTATE_running counter for a DomU.

Signed-off-by: Matias Ezequiel Vara Larsen <matias.vara@xxxxxxxx>
---
Changes in v2:
- use period instead of frec
- rely on version to ensure reading is coherent 

Changes in v1:
- change the name of the tool to xen-vcpus-stats
- set command line parameters in the same order that are passed
- remove header libs.h
- build by default
- remove errno, strerrno, "\n", and identation
- use errx when errno is not needed
- address better the number of pages requested and error msgs
- use the shared_vcpustatspage_t structure
- use the correct frame id when requesting the resource
---
 tools/misc/Makefile          |  6 +++
 tools/misc/xen-vcpus-stats.c | 87 ++++++++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+)
 create mode 100644 tools/misc/xen-vcpus-stats.c

diff --git a/tools/misc/Makefile b/tools/misc/Makefile
index 2b683819d4..837e4b50da 100644
--- a/tools/misc/Makefile
+++ b/tools/misc/Makefile
@@ -49,6 +49,7 @@ TARGETS_COPY += xenpvnetboot
 
 # Everything which needs to be built
 TARGETS_BUILD := $(filter-out $(TARGETS_COPY),$(TARGETS_ALL))
+TARGETS_BUILD += xen-vcpus-stats
 
 # ... including build-only targets
 TARGETS_BUILD-$(CONFIG_X86)    += xen-vmtrace
@@ -135,4 +136,9 @@ xencov: xencov.o
 xen-ucode: xen-ucode.o
        $(CC) $(LDFLAGS) -o $@ $< $(LDLIBS_libxenctrl) $(APPEND_LDFLAGS)
 
+xen-vcpus-stats.o: CFLAGS += $(CFLAGS_libxenforeginmemory)
+
+xen-vcpus-stats: xen-vcpus-stats.o
+       $(CC) $(LDFLAGS) -o $@ $< $(LDLIBS_libxenctrl) 
$(LDLIBS_libxenforeignmemory) $(APPEND_LDFLAGS)
+
 -include $(DEPS_INCLUDE)
diff --git a/tools/misc/xen-vcpus-stats.c b/tools/misc/xen-vcpus-stats.c
new file mode 100644
index 0000000000..29d0efb124
--- /dev/null
+++ b/tools/misc/xen-vcpus-stats.c
@@ -0,0 +1,87 @@
+#include <err.h>
+#include <errno.h>
+#include <error.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <signal.h>
+
+#include <xenctrl.h>
+#include <xenforeignmemory.h>
+#include <xen/vcpu.h>
+
+#define rmb()   asm volatile("lfence":::"memory")
+
+static sig_atomic_t interrupted;
+static void close_handler(int signum)
+{
+    interrupted = 1;
+}
+
+int main(int argc, char **argv)
+{
+    xenforeignmemory_handle *fh;
+    xenforeignmemory_resource_handle *res;
+    size_t size;
+    int rc, domid, period, vcpu;
+    shared_vcpustatspage_t * info;
+    struct sigaction act;
+    uint32_t version;
+    uint64_t value;
+
+    if (argc != 4 ) {
+        fprintf(stderr, "Usage: %s <domid> <vcpu> <period>\n", argv[0]);
+        return 1;
+    }
+
+    domid = atoi(argv[1]);
+    vcpu = atoi(argv[2]);
+    period = atoi(argv[3]);
+
+    act.sa_handler = close_handler;
+    act.sa_flags = 0;
+    sigemptyset(&act.sa_mask);
+    sigaction(SIGHUP,  &act, NULL);
+    sigaction(SIGTERM, &act, NULL);
+    sigaction(SIGINT,  &act, NULL);
+    sigaction(SIGALRM, &act, NULL);
+
+    fh = xenforeignmemory_open(NULL, 0);
+
+    if ( !fh )
+        err(1, "xenforeignmemory_open");
+
+    rc = xenforeignmemory_resource_size(
+        fh, domid, XENMEM_resource_stats_table,
+        0, &size);
+
+    if ( rc )
+        err(1, "Fail: Get size");
+
+    res = xenforeignmemory_map_resource(
+        fh, domid, XENMEM_resource_stats_table,
+        0, XENMEM_resource_stats_frame_vcpustats, size >> XC_PAGE_SHIFT,
+        (void **)&info, PROT_READ, 0);
+
+    if ( !res )
+        err(1, "Fail: Map");
+
+    while ( !interrupted ) {
+        sleep(period);
+        do {
+            version = info->vcpu_info[vcpu].version;
+            rmb();
+            value = info->vcpu_info[vcpu].runstate_running_time;
+            rmb();
+        } while ((info->vcpu_info[vcpu].version & 1) ||
+                (version != info->vcpu_info[vcpu].version));
+        printf("running_vcpu_time[%d]: %ld\n", vcpu, value);
+    }
+
+    rc = xenforeignmemory_unmap_resource(fh, res);
+    if ( rc )
+        err(1, "Fail: Unmap");
+
+    return 0;
+}
-- 
2.25.1