qga: move linux vcpu command impls to commands-linux.c

The qmp_guest_set_vcpus and qmp_guest_get_vcpus command impls in
commands-posix.c are surrounded by '#ifdef __linux__' so should
instead live in commands-linux.c

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20240712132459.3974109-3-berrange@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>

1 files changed, 141 insertions, 0 deletions

diff --git a/qga/commands-linux.c b/qga/commands-linux.c
index 214e408fcd..78580ac39d 100644
--- a/qga/commands-linux.c
+++ b/qga/commands-linux.c
@@ -13,6 +13,7 @@
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
+#include "qga-qapi-commands.h"
 #include "commands-common.h"
 #include "cutils.h"
 #include <mntent.h>
@@ -284,3 +285,143 @@ int qmp_guest_fsfreeze_do_thaw(Error **errp)
     return i;
 }
 #endif /* CONFIG_FSFREEZE */
+
+/* Transfer online/offline status between @vcpu and the guest system.
+ *
+ * On input either @errp or *@errp must be NULL.
+ *
+ * In system-to-@vcpu direction, the following @vcpu fields are accessed:
+ * - R: vcpu->logical_id
+ * - W: vcpu->online
+ * - W: vcpu->can_offline
+ *
+ * In @vcpu-to-system direction, the following @vcpu fields are accessed:
+ * - R: vcpu->logical_id
+ * - R: vcpu->online
+ *
+ * Written members remain unmodified on error.
+ */
+static void transfer_vcpu(GuestLogicalProcessor *vcpu, bool sys2vcpu,
+                          char *dirpath, Error **errp)
+{
+    int fd;
+    int res;
+    int dirfd;
+    static const char fn[] = "online";
+
+    dirfd = open(dirpath, O_RDONLY | O_DIRECTORY);
+    if (dirfd == -1) {
+        error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
+        return;
+    }
+
+    fd = openat(dirfd, fn, sys2vcpu ? O_RDONLY : O_RDWR);
+    if (fd == -1) {
+        if (errno != ENOENT) {
+            error_setg_errno(errp, errno, "open(\"%s/%s\")", dirpath, fn);
+        } else if (sys2vcpu) {
+            vcpu->online = true;
+            vcpu->can_offline = false;
+        } else if (!vcpu->online) {
+            error_setg(errp, "logical processor #%" PRId64 " can't be "
+                       "offlined", vcpu->logical_id);
+        } /* otherwise pretend successful re-onlining */
+    } else {
+        unsigned char status;
+
+        res = pread(fd, &status, 1, 0);
+        if (res == -1) {
+            error_setg_errno(errp, errno, "pread(\"%s/%s\")", dirpath, fn);
+        } else if (res == 0) {
+            error_setg(errp, "pread(\"%s/%s\"): unexpected EOF", dirpath,
+                       fn);
+        } else if (sys2vcpu) {
+            vcpu->online = (status != '0');
+            vcpu->can_offline = true;
+        } else if (vcpu->online != (status != '0')) {
+            status = '0' + vcpu->online;
+            if (pwrite(fd, &status, 1, 0) == -1) {
+                error_setg_errno(errp, errno, "pwrite(\"%s/%s\")", dirpath,
+                                 fn);
+            }
+        } /* otherwise pretend successful re-(on|off)-lining */
+
+        res = close(fd);
+        g_assert(res == 0);
+    }
+
+    res = close(dirfd);
+    g_assert(res == 0);
+}
+
+GuestLogicalProcessorList *qmp_guest_get_vcpus(Error **errp)
+{
+    GuestLogicalProcessorList *head, **tail;
+    const char *cpu_dir = "/sys/devices/system/cpu";
+    const gchar *line;
+    g_autoptr(GDir) cpu_gdir = NULL;
+    Error *local_err = NULL;
+
+    head = NULL;
+    tail = &head;
+    cpu_gdir = g_dir_open(cpu_dir, 0, NULL);
+
+    if (cpu_gdir == NULL) {
+        error_setg_errno(errp, errno, "failed to list entries: %s", cpu_dir);
+        return NULL;
+    }
+
+    while (local_err == NULL && (line = g_dir_read_name(cpu_gdir)) != NULL) {
+        GuestLogicalProcessor *vcpu;
+        int64_t id;
+        if (sscanf(line, "cpu%" PRId64, &id)) {
+            g_autofree char *path = g_strdup_printf("/sys/devices/system/cpu/"
+                                                    "cpu%" PRId64 "/", id);
+            vcpu = g_malloc0(sizeof *vcpu);
+            vcpu->logical_id = id;
+            vcpu->has_can_offline = true; /* lolspeak ftw */
+            transfer_vcpu(vcpu, true, path, &local_err);
+            QAPI_LIST_APPEND(tail, vcpu);
+        }
+    }
+
+    if (local_err == NULL) {
+        /* there's no guest with zero VCPUs */
+        g_assert(head != NULL);
+        return head;
+    }
+
+    qapi_free_GuestLogicalProcessorList(head);
+    error_propagate(errp, local_err);
+    return NULL;
+}
+
+int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList *vcpus, Error **errp)
+{
+    int64_t processed;
+    Error *local_err = NULL;
+
+    processed = 0;
+    while (vcpus != NULL) {
+        char *path = g_strdup_printf("/sys/devices/system/cpu/cpu%" PRId64 "/",
+                                     vcpus->value->logical_id);
+
+        transfer_vcpu(vcpus->value, false, path, &local_err);
+        g_free(path);
+        if (local_err != NULL) {
+            break;
+        }
+        ++processed;
+        vcpus = vcpus->next;
+    }
+
+    if (local_err != NULL) {
+        if (processed == 0) {
+            error_propagate(errp, local_err);
+        } else {
+            error_free(local_err);
+        }
+    }
+
+    return processed;
+}