[Qemu-devel] [PATCH 2/3] qga: implement qmp_guest_get_vcpus() for Linux with sysfs

[Laszlo Ersek <lersek@redhat.com>]

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 qga/commands-posix.c |   87 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 87 insertions(+), 0 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 1ad231a..d4b6bdc 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -15,6 +15,9 @@
 #include <sys/types.h>
 #include <sys/ioctl.h>
 #include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
 #include "qga/guest-agent-core.h"
 #include "qga-qmp-commands.h"
 #include "qapi/qmp/qerror.h"
@@ -1083,9 +1086,93 @@ void qmp_guest_fstrim(bool has_minimum, int64_t minimum, Error **err)
 }
 #endif
 
+#if defined(__linux__)
+#define SYSCONF_EXACT(name, err) sysconf_exact((name), #name, (err))
+
+static long sysconf_exact(int name, const char *name_str, Error **err)
+{
+    long ret;
+
+    errno = 0;
+    ret = sysconf(name);
+    if (ret == -1) {
+        if (errno == 0) {
+            error_setg(err, "sysconf(%s): value indefinite", name_str);
+        } else {
+            error_setg_errno(err, errno, "sysconf(%s)", name_str);
+        }
+    }
+    return ret;
+}
+
+/*
+ * Store a VCPU structure under the link, and return the link to store into
+ * at the next time.
+ */
+static GuestLogicalProcessorList **
+append_vcpu(int64_t logical_id, bool online, GuestLogicalProcessorList **link)
+{
+    GuestLogicalProcessor *vcpu;
+    GuestLogicalProcessorList *entry;
+
+    vcpu = g_malloc0(sizeof *vcpu);
+    vcpu->logical_id = logical_id;
+    vcpu->online = online;
+
+    entry = g_malloc0(sizeof *entry);
+    entry->value = vcpu;
+
+    *link = entry;
+    return &entry->next;
+}
+#endif
+
 GuestLogicalProcessorList *qmp_guest_get_vcpus(Error **errp)
 {
+#if defined(__linux__)
+    long current;
+    GuestLogicalProcessorList **link, *head;
+    long sc_max;
+    Error *local_err = NULL;
+
+    current = 0;
+    link = append_vcpu(current++, true, &head);
+
+    sc_max = SYSCONF_EXACT(_SC_NPROCESSORS_CONF, &local_err);
+    while (local_err == NULL && current < sc_max) {
+        char *buf;
+        FILE *f;
+
+        buf = g_strdup_printf("/sys/devices/system/cpu/cpu%ld/online",
+                              current);
+        f = fopen(buf, "r");
+        if (f == NULL) {
+            error_setg_errno(&local_err, errno, "fopen(\"%s\", \"r\")", buf);
+        } else {
+            unsigned online;
+
+            if (fscanf(f, "%u", &online) != 1) {
+                error_setg(&local_err, "failed to read or parse \"%s\"", buf);
+            } else {
+                link = append_vcpu(current++, online != 0, link);
+            }
+
+            if (fclose(f) == EOF && local_err == NULL) {
+                error_setg_errno(&local_err, errno, "fclose(\"%s\")", buf);
+            }
+        }
+        g_free(buf);
+    }
+
+    if (local_err == NULL) {
+        return head;
+    }
+
+    qapi_free_GuestLogicalProcessorList(head);
+    error_propagate(errp, local_err);
+#else
     error_set(errp, QERR_UNSUPPORTED);
+#endif
     return NULL;
 }
 
-- 
1.7.1