vfio: Add VM state change handler to know state of VM

VM state change handler is called on change in VM's state. Based on
VM state, VFIO device state should be changed.
Added read/write helper functions for migration region.
Added function to set device_state.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
[aw: lx -> HWADDR_PRIx, remove redundant parens]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

hw/vfio/migration.c

@@ -10,6 +10,7 @@
 #include "qemu/osdep.h"
 #include <linux/vfio.h>
 
+#include "sysemu/runstate.h"
 #include "hw/vfio/vfio-common.h"
 #include "cpu.h"
 #include "migration/migration.h"
@@ -22,6 +23,157 @@
 #include "exec/ram_addr.h"
 #include "pci.h"
 #include "trace.h"
+#include "hw/hw.h"
+
+static inline int vfio_mig_access(VFIODevice *vbasedev, void *val, int count,
+                                  off_t off, bool iswrite)
+{
+    int ret;
+
+    ret = iswrite ? pwrite(vbasedev->fd, val, count, off) :
+                    pread(vbasedev->fd, val, count, off);
+    if (ret < count) {
+        error_report("vfio_mig_%s %d byte %s: failed at offset 0x%"
+                     HWADDR_PRIx", err: %s", iswrite ? "write" : "read", count,
+                     vbasedev->name, off, strerror(errno));
+        return (ret < 0) ? ret : -EINVAL;
+    }
+    return 0;
+}
+
+static int vfio_mig_rw(VFIODevice *vbasedev, __u8 *buf, size_t count,
+                       off_t off, bool iswrite)
+{
+    int ret, done = 0;
+    __u8 *tbuf = buf;
+
+    while (count) {
+        int bytes = 0;
+
+        if (count >= 8 && !(off % 8)) {
+            bytes = 8;
+        } else if (count >= 4 && !(off % 4)) {
+            bytes = 4;
+        } else if (count >= 2 && !(off % 2)) {
+            bytes = 2;
+        } else {
+            bytes = 1;
+        }
+
+        ret = vfio_mig_access(vbasedev, tbuf, bytes, off, iswrite);
+        if (ret) {
+            return ret;
+        }
+
+        count -= bytes;
+        done += bytes;
+        off += bytes;
+        tbuf += bytes;
+    }
+    return done;
+}
+
+#define vfio_mig_read(f, v, c, o)       vfio_mig_rw(f, (__u8 *)v, c, o, false)
+#define vfio_mig_write(f, v, c, o)      vfio_mig_rw(f, (__u8 *)v, c, o, true)
+
+#define VFIO_MIG_STRUCT_OFFSET(f)       \
+                                 offsetof(struct vfio_device_migration_info, f)
+/*
+ * Change the device_state register for device @vbasedev. Bits set in @mask
+ * are preserved, bits set in @value are set, and bits not set in either @mask
+ * or @value are cleared in device_state. If the register cannot be accessed,
+ * the resulting state would be invalid, or the device enters an error state,
+ * an error is returned.
+ */
+
+static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask,
+                                    uint32_t value)
+{
+    VFIOMigration *migration = vbasedev->migration;
+    VFIORegion *region = &migration->region;
+    off_t dev_state_off = region->fd_offset +
+                          VFIO_MIG_STRUCT_OFFSET(device_state);
+    uint32_t device_state;
+    int ret;
+
+    ret = vfio_mig_read(vbasedev, &device_state, sizeof(device_state),
+                        dev_state_off);
+    if (ret < 0) {
+        return ret;
+    }
+
+    device_state = (device_state & mask) | value;
+
+    if (!VFIO_DEVICE_STATE_VALID(device_state)) {
+        return -EINVAL;
+    }
+
+    ret = vfio_mig_write(vbasedev, &device_state, sizeof(device_state),
+                         dev_state_off);
+    if (ret < 0) {
+        int rret;
+
+        rret = vfio_mig_read(vbasedev, &device_state, sizeof(device_state),
+                             dev_state_off);
+
+        if ((rret < 0) || (VFIO_DEVICE_STATE_IS_ERROR(device_state))) {
+            hw_error("%s: Device in error state 0x%x", vbasedev->name,
+                     device_state);
+            return rret ? rret : -EIO;
+        }
+        return ret;
+    }
+
+    migration->device_state = device_state;
+    trace_vfio_migration_set_state(vbasedev->name, device_state);
+    return 0;
+}
+
+static void vfio_vmstate_change(void *opaque, int running, RunState state)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+    uint32_t value, mask;
+    int ret;
+
+    if (vbasedev->migration->vm_running == running) {
+        return;
+    }
+
+    if (running) {
+        /*
+         * Here device state can have one of _SAVING, _RESUMING or _STOP bit.
+         * Transition from _SAVING to _RUNNING can happen if there is migration
+         * failure, in that case clear _SAVING bit.
+         * Transition from _RESUMING to _RUNNING occurs during resuming
+         * phase, in that case clear _RESUMING bit.
+         * In both the above cases, set _RUNNING bit.
+         */
+        mask = ~VFIO_DEVICE_STATE_MASK;
+        value = VFIO_DEVICE_STATE_RUNNING;
+    } else {
+        /*
+         * Here device state could be either _RUNNING or _SAVING|_RUNNING. Reset
+         * _RUNNING bit
+         */
+        mask = ~VFIO_DEVICE_STATE_RUNNING;
+        value = 0;
+    }
+
+    ret = vfio_migration_set_state(vbasedev, mask, value);
+    if (ret) {
+        /*
+         * Migration should be aborted in this case, but vm_state_notify()
+         * currently does not support reporting failures.
+         */
+        error_report("%s: Failed to set device state 0x%x", vbasedev->name,
+                     (migration->device_state & mask) | value);
+        qemu_file_set_error(migrate_get_current()->to_dst_file, ret);
+    }
+    vbasedev->migration->vm_running = running;
+    trace_vfio_vmstate_change(vbasedev->name, running, RunState_str(state),
+            (migration->device_state & mask) | value);
+}
 
 static void vfio_migration_exit(VFIODevice *vbasedev)
 {
@@ -38,6 +190,7 @@ static int vfio_migration_init(VFIODevice *vbasedev,
 {
     int ret;
     Object *obj;
+    VFIOMigration *migration;
 
     if (!vbasedev->ops->vfio_get_object) {
         return -EINVAL;
@@ -64,6 +217,10 @@ static int vfio_migration_init(VFIODevice *vbasedev,
         ret = -EINVAL;
         goto err;
     }
+
+    migration = vbasedev->migration;
+    migration->vm_state = qemu_add_vm_change_state_handler(vfio_vmstate_change,
+                                                           vbasedev);
     return 0;
 
 err:
@@ -111,6 +268,9 @@ add_blocker:
 void vfio_migration_finalize(VFIODevice *vbasedev)
 {
     if (vbasedev->migration) {
+        VFIOMigration *migration = vbasedev->migration;
+
+        qemu_del_vm_change_state_handler(migration->vm_state);
         vfio_migration_exit(vbasedev);
     }
 

hw/vfio/trace-events

@@ -148,3 +148,5 @@ vfio_display_edid_write_error(void) ""
 
 # migration.c
 vfio_migration_probe(const char *name, uint32_t index) " (%s) Region %d"
+vfio_migration_set_state(const char *name, uint32_t state) " (%s) state %d"
+vfio_vmstate_change(const char *name, int running, const char *reason, uint32_t dev_state) " (%s) running %d reason %s device state %d"

include/hw/vfio/vfio-common.h

@@ -29,6 +29,7 @@
 #ifdef CONFIG_LINUX
 #include <linux/vfio.h>
 #endif
+#include "sysemu/sysemu.h"
 
 #define VFIO_MSG_PREFIX "vfio %s: "
 
@@ -58,7 +59,10 @@ typedef struct VFIORegion {
 } VFIORegion;
 
 typedef struct VFIOMigration {
+    VMChangeStateEntry *vm_state;
     VFIORegion region;
+    uint32_t device_state;
+    int vm_running;
 } VFIOMigration;
 
 typedef struct VFIOAddressSpace {