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Re: [PATCH v26 05/17] vfio: Add VM state change handler to know state of
From: |
Alex Williamson |
Subject: |
Re: [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM |
Date: |
Fri, 25 Sep 2020 14:20:23 -0600 |
On Wed, 23 Sep 2020 04:54:07 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:
> VM state change handler gets called on change in VM's state. This is used to
> set
> VFIO device state to _RUNNING.
>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> hw/vfio/migration.c | 136
> ++++++++++++++++++++++++++++++++++++++++++
> hw/vfio/trace-events | 3 +-
> include/hw/vfio/vfio-common.h | 4 ++
> 3 files changed, 142 insertions(+), 1 deletion(-)
>
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 2f760f1f9c47..a30d628ba963 100644
> --- a/hw/vfio/migration.c
> +++ b/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 +23,58 @@
> #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 %s: failed at offset 0x%lx, err: %s",
> + iswrite ? "write" : "read", count * 8,
> + vbasedev->name, off, strerror(errno));
This would suggest from the log that there's, for example, a
vfio_mig_read8 function, which doesn't exist.
> + 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)
>
> static void vfio_migration_region_exit(VFIODevice *vbasedev)
> {
> @@ -70,6 +123,82 @@ err:
> return ret;
> }
>
> +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 +
> + offsetof(struct vfio_device_migration_info,
> 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;
Agree with Connie that mask and value args are not immediately obvious
how they're used. I don't have a naming convention that would be more
clear and the names do make some sense once they're understood, but a
comment to indicate mask bits are preserved, value bits are set,
remaining bits are cleared would probably help the reader.
> +
> + 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) {
> + ret = vfio_mig_read(vbasedev, &device_state, sizeof(device_state),
> + dev_state_off);
> + if (ret < 0) {
> + return ret;
Seems like we're in pretty bad shape here, should this be combined with
below to trigger a hw_error?
> + }
> +
> + if (VFIO_DEVICE_STATE_IS_ERROR(device_state)) {
> + hw_error("%s: Device is in error state 0x%x",
> + vbasedev->name, device_state);
> + return -EFAULT;
> + }
> + }
> +
> + vbasedev->device_state = device_state;
> + trace_vfio_migration_set_state(vbasedev->name, device_state);
> + return 0;
So we return success even if we failed to write the desired state as
long as we were able to read back any non-error state?
vbasedev->device_state remains correct, but it seems confusing form a
caller perspective that a set-state can succeed but it's then necessary
to check the state.
> +}
> +
> +static void vfio_vmstate_change(void *opaque, int running, RunState state)
> +{
> + VFIODevice *vbasedev = opaque;
> +
> + if ((vbasedev->vm_running != running)) {
> + int ret;
> + uint32_t value = 0, mask = 0;
> +
> + if (running) {
> + value = VFIO_DEVICE_STATE_RUNNING;
> + if (vbasedev->device_state & VFIO_DEVICE_STATE_RESUMING) {
> + mask = ~VFIO_DEVICE_STATE_RESUMING;
> + }
> + } else {
> + mask = ~VFIO_DEVICE_STATE_RUNNING;
> + }
> +
> + ret = vfio_migration_set_state(vbasedev, mask, value);
> + if (ret) {
> + /*
> + * vm_state_notify() doesn't support reporting failure. If such
> + * error reporting support added in furure, migration should be
> + * aborted.
> + */
> + error_report("%s: Failed to set device state 0x%x",
> + vbasedev->name, value & mask);
> + }
Here for instance we assume that success means the device is now in the
desired state, but we'd actually need to evaluate
vbasedev->device_state to determine that.
> + vbasedev->vm_running = running;
> + trace_vfio_vmstate_change(vbasedev->name, running,
> RunState_str(state),
> + value & mask);
> + }
> +}
> +
> static int vfio_migration_init(VFIODevice *vbasedev,
> struct vfio_region_info *info)
> {
> @@ -87,8 +216,11 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> vbasedev->name);
> g_free(vbasedev->migration);
> vbasedev->migration = NULL;
> + return ret;
> }
>
> + vbasedev->vm_state =
> qemu_add_vm_change_state_handler(vfio_vmstate_change,
> + vbasedev);
> return ret;
> }
>
> @@ -131,6 +263,10 @@ add_blocker:
>
> void vfio_migration_finalize(VFIODevice *vbasedev)
> {
> + if (vbasedev->vm_state) {
> + qemu_del_vm_change_state_handler(vbasedev->vm_state);
> + }
> +
> if (vbasedev->migration_blocker) {
> migrate_del_blocker(vbasedev->migration_blocker);
> error_free(vbasedev->migration_blocker);
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index 8fe913175d85..6524734bf7b4 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -149,4 +149,5 @@ vfio_display_edid_write_error(void) ""
>
> # migration.c
> vfio_migration_probe(const char *name, uint32_t index) " (%s) Region %d"
> -
> +vfio_migration_set_state(char *name, uint32_t state) " (%s) state %d"
> +vfio_vmstate_change(char *name, int running, const char *reason, uint32_t
> dev_state) " (%s) running %d reason %s device state %d"
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index 8275c4c68f45..25e3b1a3b90a 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/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: "
>
> @@ -119,6 +120,9 @@ typedef struct VFIODevice {
> unsigned int flags;
> VFIOMigration *migration;
> Error *migration_blocker;
> + VMChangeStateEntry *vm_state;
> + uint32_t device_state;
> + int vm_running;
Could these be placed in VFIOMigration? Thanks,
Alex
> } VFIODevice;
>
> struct VFIODeviceOps {
- [PATCH v26 03/17] vfio: Add save and load functions for VFIO PCI devices, (continued)
- [PATCH v26 03/17] vfio: Add save and load functions for VFIO PCI devices, Kirti Wankhede, 2020/09/22
- [PATCH v26 04/17] vfio: Add migration region initialization and finalize function, Kirti Wankhede, 2020/09/22
- [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM, Kirti Wankhede, 2020/09/22
- [PATCH v26 06/17] vfio: Add migration state change notifier, Kirti Wankhede, 2020/09/22
- [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device, Kirti Wankhede, 2020/09/22
- [PATCH v26 08/17] vfio: Add save state functions to SaveVMHandlers, Kirti Wankhede, 2020/09/22