* Alex Williamson (alex.william...@redhat.com) wrote:
> On Wed, 24 Jun 2020 00:51:06 +0530
> Kirti Wankhede <kwankh...@nvidia.com> wrote:
>
> > On 6/23/2020 4:20 AM, Alex Williamson wrote:
> > > On Sun, 21 Jun 2020 01:51:16 +0530
> > > Kirti Wankhede <kwankh...@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 <kwankh...@nvidia.com>
> > >> Reviewed-by: Neo Jia <c...@nvidia.com>
> > >> ---
> > >> hw/vfio/migration.c | 92
> > >> ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >> hw/vfio/trace-events | 2 ++
> > >> 2 files changed, 94 insertions(+)
> > >>
> > >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> > >> index e30bd8768701..133bb5b1b3b2 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"
> > >> @@ -24,6 +27,17 @@
> > >> #include "pci.h"
> > >> #include "trace.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 void vfio_migration_region_exit(VFIODevice *vbasedev)
> > >> {
> > >> VFIOMigration *migration = vbasedev->migration;
> > >> @@ -126,6 +140,65 @@ 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();
> > >> + if (ret) {
> > >> + error_report("%s: Failed to mmap VFIO migration region %d:
> > >> %s",
> > >> + vbasedev->name, migration->region.nr,
> > >> + strerror(-ret));
> > >> + return ret;
> > >
> > > OTOH to my previous comments, this shouldn't be fatal, right? mmaps
> > > are optional anyway so it should be sufficient to push an error report
> > > to explain why this might be slower than normal, but we can still
> > > proceed.
> > >
> >
> > Right, defining region to be sparse mmap is optional.
> > migration->region.mmaps is set if vendor driver defines sparse mmapable
> > regions and VFIO_REGION_INFO_FLAG_MMAP flag is set. If this flag is set
> > then error on mmap() should be fatal.
> >
> > If there is not mmapable region, then migration will proceed.
>
> It's both optional for the vendor to define sparse mmap support (or any
> mmap support) and optional for the user to make use of it. The user
> can recover from an mmap failure by using read/write accesses. The
> vendor MUST support this. It doesn't make sense to worry about
> aborting the VM in replying to comments for 05/17, where it's not clear
> how we proceed, yet intentionally cause a fatal error here when there
> is a very clear path to proceed.
>
> > >> + }
> > >> + }
> > >> +
> > >> + 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;
> > >> + }
> > >
> > > We seem to be lacking support in the callers for detecting if the
> > > device is in an error state. I'm not sure what our options are
> > > though, maybe only a hw_error().
> > >
> >
> > Returning error here fails migration process. And if device is in error
> > state, any application running inside VM using this device would fail.
> > I think, there is no need to take any special action here by detecting
> > device error state.
>
> If QEMU knows a device has failed, it seems like it would make sense to
> stop the VM, otherwise we risk an essentially endless assortment of
> ways that the user might notice the guest isn't behaving normally, some
> maybe even causing the user to lose data. Thanks,
With GPUs especially though we can get into messy states where only the
GPU is toast; for example you might get this if your GUI
starts/exits/crashes during a migration - that's a bit too common to
kill a VM that might have useful data on it.
Dave
> Alex
>
> > >> +
> > >> + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
> > >> +
> > >> + 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;
> > >> @@ -180,6 +253,7 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> > >> struct vfio_region_info *info)
> > >> {
> > >> int ret;
> > >> + char id[256] = "";
> > >>
> > >> vbasedev->migration = g_new0(VFIOMigration, 1);
> > >>
> > >> @@ -192,6 +266,24 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> > >> return ret;
> > >> }
> > >>
> > >> + if (vbasedev->ops->vfio_get_object) {
> > >
> > > Nit, vfio_migration_region_init() would have failed already if this were
> > > not available. Perhaps do the test once at the start of this function
> > > instead? Thanks,
> > >
> >
> > Ok, will do that.
> >
> > Thanks,
> > Kirti
> >
> >
> > > Alex
> > >
> > >> + Object *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);
> > >> + }
> > >> + }
> > >> + }
> > >> + 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 bd3d47b005cb..86c18def016e 100644
> > >> --- a/hw/vfio/trace-events
> > >> +++ b/hw/vfio/trace-events
> > >> @@ -149,3 +149,5 @@ 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)"
> > >
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
