Re: [PATCH v27 05/17] vfio: Add VM state change handler to know state of VM

[Alex Williamson]

On Thu, 22 Oct 2020 23:11:39 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 10/22/2020 10:05 PM, Alex Williamson wrote:
> > On Thu, 22 Oct 2020 16:41:55 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> 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>
> >> ---
> >>   hw/vfio/migration.c           | 158 
> >> ++++++++++++++++++++++++++++++++++++++++++
> >>   hw/vfio/trace-events          |   2 +
> >>   include/hw/vfio/vfio-common.h |   4 ++
> >>   3 files changed, 164 insertions(+)
> >>
> >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> >> index 5f74a3ad1d72..34f39c7e2e28 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 +23,157 @@
> >>   #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%lx, 
> >> 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_region_exit(VFIODevice *vbasedev)
> >>   {
> >> @@ -71,6 +223,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> >>       }
> >>   
> >>       vbasedev->migration = migration;
> >> +    migration->vm_state = 
> >> qemu_add_vm_change_state_handler(vfio_vmstate_change,
> >> +                                                          vbasedev);
> >>       return 0;
> >>   
> >>   err:
> >> @@ -118,6 +272,10 @@ add_blocker:
> >>   
> >>   void vfio_migration_finalize(VFIODevice *vbasedev)
> >>   {
> >> +    if (vbasedev->migration->vm_state) {
> >> +        qemu_del_vm_change_state_handler(vbasedev->migration->vm_state);
> >> +    }  
> > 
> > 
> > This looks like a segfault, vfio_migration_teardown() is eventually
> > called unconditionally.  The next patch modifies this function further,
> > but never checks that vbasedev->migration is non-NULL.  Thanks,
> >   
> 
> Yup.
> Updated patch 4, 5 and 6. So now vfio_migration_finalize() looks like:
> 
> void vfio_migration_finalize(VFIODevice *vbasedev)
> {
>      VFIOMigration *migration = vbasedev->migration;
> 
>      if (migration) {
>          if (migration->migration_state.notify) {
>  
> remove_migration_state_change_notifier(&migration->migration_state);
>          }
> 
>          if (migration->vm_state) {
>              qemu_del_vm_change_state_handler(migration->vm_state);
>          }

We should be able to remove these based only on migration being
non-NULL, their setup cannot fail once we've setup the migration
pointer.  Thanks,

Alex

> 
>          vfio_migration_region_exit(vbasedev);
>          g_free(vbasedev->migration);
>          vbasedev->migration = NULL;
>      }
> 
>      if (vbasedev->migration_blocker) {
>          migrate_del_blocker(vbasedev->migration_blocker);
>          error_free(vbasedev->migration_blocker);
>          vbasedev->migration_blocker = NULL;
>      }
> }
> 
> Thanks,
> Kirti
> 
> > Alex
> > 
> >   
> >> +
> >>       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 9ced5ec6277c..41de81f12f60 100644
> >> --- a/hw/vfio/trace-events
> >> +++ b/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"
> >> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >> index 8275c4c68f45..9a571f1fb552 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: "
> >>   
> >> @@ -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 {  
> >   
>