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Re: [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device
From: |
Alex Williamson |
Subject: |
Re: [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device |
Date: |
Fri, 25 Sep 2020 14:20:46 -0600 |
On Wed, 23 Sep 2020 04:54:09 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:
> Define flags to be used as delimeter in migration file stream.
> Added .save_setup and .save_cleanup functions. Mapped & unmapped migration
> region from these functions at source during saving or pre-copy phase.
> Set VFIO device state depending on VM's state. During live migration, VM is
> running when .save_setup is called, _SAVING | _RUNNING state is set for VFIO
> device. During save-restore, VM is paused, _SAVING state is set for VFIO
> device.
>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
> hw/vfio/migration.c | 91
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
> hw/vfio/trace-events | 2 ++
> 2 files changed, 93 insertions(+)
>
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index f650fe9fc3c8..8e8adaa25779 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -8,12 +8,15 @@
> */
>
> #include "qemu/osdep.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/cutils.h"
> #include <linux/vfio.h>
>
> #include "sysemu/runstate.h"
> #include "hw/vfio/vfio-common.h"
> #include "cpu.h"
> #include "migration/migration.h"
> +#include "migration/vmstate.h"
> #include "migration/qemu-file.h"
> #include "migration/register.h"
> #include "migration/blocker.h"
> @@ -25,6 +28,17 @@
> #include "trace.h"
> #include "hw/hw.h"
>
> +/*
> + * Flags used as delimiter:
> + * 0xffffffff => MSB 32-bit all 1s
> + * 0xef10 => emulated (virtual) function IO
> + * 0x0000 => 16-bits reserved for flags
> + */
> +#define VFIO_MIG_FLAG_END_OF_STATE (0xffffffffef100001ULL)
> +#define VFIO_MIG_FLAG_DEV_CONFIG_STATE (0xffffffffef100002ULL)
> +#define VFIO_MIG_FLAG_DEV_SETUP_STATE (0xffffffffef100003ULL)
> +#define VFIO_MIG_FLAG_DEV_DATA_STATE (0xffffffffef100004ULL)
> +
> static inline int vfio_mig_access(VFIODevice *vbasedev, void *val, int count,
> off_t off, bool iswrite)
> {
> @@ -166,6 +180,65 @@ static int vfio_migration_set_state(VFIODevice
> *vbasedev, uint32_t mask,
> return 0;
> }
>
> +/* ---------------------------------------------------------------------- */
> +
> +static int vfio_save_setup(QEMUFile *f, void *opaque)
> +{
> + VFIODevice *vbasedev = opaque;
> + VFIOMigration *migration = vbasedev->migration;
> + int ret;
> +
> + trace_vfio_save_setup(vbasedev->name);
> +
> + qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE);
> +
> + if (migration->region.mmaps) {
> + qemu_mutex_lock_iothread();
> + ret = vfio_region_mmap(&migration->region);
> + qemu_mutex_unlock_iothread();
Please add a comment identifying why the iothread mutex lock is
necessary here.
> + if (ret) {
> + error_report("%s: Failed to mmap VFIO migration region %d: %s",
> + vbasedev->name, migration->region.nr,
We don't support multiple migration regions, is it useful to include
the region index here?
> + strerror(-ret));
> + error_report("%s: Falling back to slow path", vbasedev->name);
> + }
> + }
> +
> + ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_MASK,
> + VFIO_DEVICE_STATE_SAVING);
> + if (ret) {
> + error_report("%s: Failed to set state SAVING", vbasedev->name);
> + return ret;
> + }
Again, doesn't match the function semantics that success only means the
device is in a non-error state, maybe the one that was asked for.
> +
> + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
What's the overall purpose of writing these markers into the migration
stream? vfio_load_state() doesn't do anything with this other than
validate that the end-of-state immediately follows. Is this a
placeholder for something in the future?
> +
> + ret = qemu_file_get_error(f);
> + if (ret) {
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static void vfio_save_cleanup(void *opaque)
> +{
> + VFIODevice *vbasedev = opaque;
> + VFIOMigration *migration = vbasedev->migration;
> +
> + if (migration->region.mmaps) {
> + vfio_region_unmap(&migration->region);
> + }
> + trace_vfio_save_cleanup(vbasedev->name);
> +}
> +
> +static SaveVMHandlers savevm_vfio_handlers = {
> + .save_setup = vfio_save_setup,
> + .save_cleanup = vfio_save_cleanup,
> +};
> +
> +/* ---------------------------------------------------------------------- */
> +
> static void vfio_vmstate_change(void *opaque, int running, RunState state)
> {
> VFIODevice *vbasedev = opaque;
> @@ -225,6 +298,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> struct vfio_region_info *info)
> {
> int ret = -EINVAL;
> + char id[256] = "";
> + Object *obj;
>
> if (!vbasedev->ops->vfio_get_object) {
> return ret;
> @@ -241,6 +316,22 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> return ret;
> }
>
> + obj = vbasedev->ops->vfio_get_object(vbasedev);
> +
> + if (obj) {
> + DeviceState *dev = DEVICE(obj);
> + char *oid = vmstate_if_get_id(VMSTATE_IF(dev));
> +
> + if (oid) {
> + pstrcpy(id, sizeof(id), oid);
> + pstrcat(id, sizeof(id), "/");
> + g_free(oid);
> + }
> + }
Here's where vfio_migration_init() starts using vfio_get_object() as I
referenced back on patch 04. We might as well get the object before
calling vfio_migration_region_init() and then pass the object. The
conditional branch to handle obj is strange here too, it's fatal if
vfio_migration_region_init() doesn't find an object, why do we handle
it as optional here? Also, what is this doing? Comments would be
nice... Thanks,
Alex
> + pstrcat(id, sizeof(id), "vfio");
> +
> + register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1,
> &savevm_vfio_handlers,
> + vbasedev);
> vbasedev->vm_state =
> qemu_add_vm_change_state_handler(vfio_vmstate_change,
> vbasedev);
> vbasedev->migration_state.notify = vfio_migration_state_notifier;
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index bcb3fa7314d7..982d8dccb219 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -152,3 +152,5 @@ 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"
> vfio_migration_state_notifier(const char *name, const char *state) " (%s)
> state %s"
> +vfio_save_setup(const char *name) " (%s)"
> +vfio_save_cleanup(const char *name) " (%s)"
- Re: [PATCH v26 04/17] vfio: Add migration region initialization and finalize function, (continued)
- [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
- [PATCH v26 09/17] vfio: Add load state functions to SaveVMHandlers, Kirti Wankhede, 2020/09/22
- [PATCH v26 10/17] memory: Set DIRTY_MEMORY_MIGRATION when IOMMU is enabled, Kirti Wankhede, 2020/09/22
- [PATCH v26 12/17] vfio: Add function to start and stop dirty pages tracking, Kirti Wankhede, 2020/09/22
- [PATCH v26 11/17] vfio: Get migration capability flags for container, Kirti Wankhede, 2020/09/22
- [PATCH v26 13/17] vfio: create mapped iova list when vIOMMU is enabled, Kirti Wankhede, 2020/09/22