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Subject: Re: [PATCH v27 09/17] vfio: Add load state functions to SaveVMHandlers
To: Alex Williamson <alex.williamson@redhat.com>
References: <1603365127-14202-1-git-send-email-kwankhede@nvidia.com>
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From: Kirti Wankhede <kwankhede@nvidia.com>
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Date: Fri, 23 Oct 2020 15:29:01 +0530
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On 10/23/2020 1:20 AM, Alex Williamson wrote:
> On Thu, 22 Oct 2020 16:41:59 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> Sequence  during _RESUMING device state:
>> While data for this device is available, repeat below steps:
>> a. read data_offset from where user application should write data.
>> b. write data of data_size to migration region from data_offset.
>> c. write data_size which indicates vendor driver that data is written in
>>     staging buffer.
>>
>> For user, data is opaque. User should write data in the same order as
>> received.
>>
>> 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  | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>   hw/vfio/trace-events |   3 +
>>   2 files changed, 195 insertions(+)
>>
>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
>> index 5506cef15d88..46d05d230e2a 100644
>> --- a/hw/vfio/migration.c
>> +++ b/hw/vfio/migration.c
>> @@ -257,6 +257,77 @@ static int vfio_save_buffer(QEMUFile *f, VFIODevice *vbasedev, uint64_t *size)
>>       return ret;
>>   }
>>   
>> +static int vfio_load_buffer(QEMUFile *f, VFIODevice *vbasedev,
>> +                            uint64_t data_size)
>> +{
>> +    VFIORegion *region = &vbasedev->migration->region;
>> +    uint64_t data_offset = 0, size, report_size;
>> +    int ret;
>> +
>> +    do {
>> +        ret = vfio_mig_read(vbasedev, &data_offset, sizeof(data_offset),
>> +                      region->fd_offset + VFIO_MIG_STRUCT_OFFSET(data_offset));
>> +        if (ret < 0) {
>> +            return ret;
>> +        }
>> +
>> +        if (data_offset + data_size > region->size) {
>> +            /*
>> +             * If data_size is greater than the data section of migration region
>> +             * then iterate the write buffer operation. This case can occur if
>> +             * size of migration region at destination is smaller than size of
>> +             * migration region at source.
>> +             */
>> +            report_size = size = region->size - data_offset;
>> +            data_size -= size;
>> +        } else {
>> +            report_size = size = data_size;
>> +            data_size = 0;
>> +        }
>> +
>> +        trace_vfio_load_state_device_data(vbasedev->name, data_offset, size);
>> +
>> +        while (size) {
>> +            void *buf;
>> +            uint64_t sec_size;
>> +            bool buf_alloc = false;
>> +
>> +            buf = get_data_section_size(region, data_offset, size, &sec_size);
>> +
>> +            if (!buf) {
>> +                buf = g_try_malloc(sec_size);
>> +                if (!buf) {
>> +                    error_report("%s: Error allocating buffer ", __func__);
>> +                    return -ENOMEM;
>> +                }
>> +                buf_alloc = true;
>> +            }
>> +
>> +            qemu_get_buffer(f, buf, sec_size);
>> +
>> +            if (buf_alloc) {
>> +                ret = vfio_mig_write(vbasedev, buf, sec_size,
>> +                        region->fd_offset + data_offset);
>> +                g_free(buf);
>> +
>> +                if (ret < 0) {
>> +                    return ret;
>> +                }
>> +            }
>> +            size -= sec_size;
>> +            data_offset += sec_size;
>> +        }
>> +
>> +        ret = vfio_mig_write(vbasedev, &report_size, sizeof(report_size),
>> +                        region->fd_offset + VFIO_MIG_STRUCT_OFFSET(data_size));
>> +        if (ret < 0) {
>> +            return ret;
>> +        }
>> +    } while (data_size);
>> +
>> +    return 0;
>> +}
>> +
>>   static int vfio_update_pending(VFIODevice *vbasedev)
>>   {
>>       VFIOMigration *migration = vbasedev->migration;
>> @@ -293,6 +364,33 @@ static int vfio_save_device_config_state(QEMUFile *f, void *opaque)
>>       return qemu_file_get_error(f);
>>   }
>>   
>> +static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
>> +{
>> +    VFIODevice *vbasedev = opaque;
>> +    uint64_t data;
>> +
>> +    if (vbasedev->ops && vbasedev->ops->vfio_load_config) {
>> +        int ret;
>> +
>> +        ret = vbasedev->ops->vfio_load_config(vbasedev, f);
>> +        if (ret) {
>> +            error_report("%s: Failed to load device config space",
>> +                         vbasedev->name);
>> +            return ret;
>> +        }
>> +    }
>> +
>> +    data = qemu_get_be64(f);
>> +    if (data != VFIO_MIG_FLAG_END_OF_STATE) {
>> +        error_report("%s: Failed loading device config space, "
>> +                     "end flag incorrect 0x%"PRIx64, vbasedev->name, data);
>> +        return -EINVAL;
>> +    }
>> +
>> +    trace_vfio_load_device_config_state(vbasedev->name);
>> +    return qemu_file_get_error(f);
>> +}
>> +
>>   /* ---------------------------------------------------------------------- */
>>   
>>   static int vfio_save_setup(QEMUFile *f, void *opaque)
>> @@ -477,12 +575,106 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
>>       return ret;
>>   }
>>   
>> +static int vfio_load_setup(QEMUFile *f, void *opaque)
>> +{
>> +    VFIODevice *vbasedev = opaque;
>> +    VFIOMigration *migration = vbasedev->migration;
>> +    int ret = 0;
>> +
>> +    if (migration->region.mmaps) {
>> +        ret = vfio_region_mmap(&migration->region);
> 
> 
> Checking, are we in the right thread context not to require locking the
> iothread as we did in vfio_save_setup()?
> 
> 

iothread lock is held when calling load_setup.

>> +        if (ret) {
>> +            error_report("%s: Failed to mmap VFIO migration region %d: %s",
>> +                         vbasedev->name, migration->region.nr,
>> +                         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_RESUMING);
>> +    if (ret) {
>> +        error_report("%s: Failed to set state RESUMING", vbasedev->name);
>> +        if (migration->region.mmaps) {
>> +            vfio_region_unmap(&migration->region);
>> +        }
>> +    }
>> +    return ret;
>> +}
>> +
>> +static int vfio_load_cleanup(void *opaque)
>> +{
>> +    vfio_save_cleanup(opaque);
> 
> 
> The tracing in there is going to be rather confusing.  Thanks,
> 

Updating patch 7 and this to separate tracing.

Thanks,
Kirti

> Alex
> 
> 
>> +    return 0;
>> +}
>> +
>> +static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
>> +{
>> +    VFIODevice *vbasedev = opaque;
>> +    int ret = 0;
>> +    uint64_t data;
>> +
>> +    data = qemu_get_be64(f);
>> +    while (data != VFIO_MIG_FLAG_END_OF_STATE) {
>> +
>> +        trace_vfio_load_state(vbasedev->name, data);
>> +
>> +        switch (data) {
>> +        case VFIO_MIG_FLAG_DEV_CONFIG_STATE:
>> +        {
>> +            ret = vfio_load_device_config_state(f, opaque);
>> +            if (ret) {
>> +                return ret;
>> +            }
>> +            break;
>> +        }
>> +        case VFIO_MIG_FLAG_DEV_SETUP_STATE:
>> +        {
>> +            data = qemu_get_be64(f);
>> +            if (data == VFIO_MIG_FLAG_END_OF_STATE) {
>> +                return ret;
>> +            } else {
>> +                error_report("%s: SETUP STATE: EOS not found 0x%"PRIx64,
>> +                             vbasedev->name, data);
>> +                return -EINVAL;
>> +            }
>> +            break;
>> +        }
>> +        case VFIO_MIG_FLAG_DEV_DATA_STATE:
>> +        {
>> +            uint64_t data_size = qemu_get_be64(f);
>> +
>> +            if (data_size) {
>> +                ret = vfio_load_buffer(f, vbasedev, data_size);
>> +                if (ret < 0) {
>> +                    return ret;
>> +                }
>> +            }
>> +            break;
>> +        }
>> +        default:
>> +            error_report("%s: Unknown tag 0x%"PRIx64, vbasedev->name, data);
>> +            return -EINVAL;
>> +        }
>> +
>> +        data = qemu_get_be64(f);
>> +        ret = qemu_file_get_error(f);
>> +        if (ret) {
>> +            return ret;
>> +        }
>> +    }
>> +    return ret;
>> +}
>> +
>>   static SaveVMHandlers savevm_vfio_handlers = {
>>       .save_setup = vfio_save_setup,
>>       .save_cleanup = vfio_save_cleanup,
>>       .save_live_pending = vfio_save_pending,
>>       .save_live_iterate = vfio_save_iterate,
>>       .save_live_complete_precopy = vfio_save_complete_precopy,
>> +    .load_setup = vfio_load_setup,
>> +    .load_cleanup = vfio_load_cleanup,
>> +    .load_state = vfio_load_state,
>>   };
>>   
>>   /* ---------------------------------------------------------------------- */
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index 9f5712dab1ea..4804cc266d44 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -159,3 +159,6 @@ vfio_save_device_config_state(const char *name) " (%s)"
>>   vfio_save_pending(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t compatible) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" compatible 0x%"PRIx64
>>   vfio_save_iterate(const char *name, int data_size) " (%s) data_size %d"
>>   vfio_save_complete_precopy(const char *name) " (%s)"
>> +vfio_load_device_config_state(const char *name) " (%s)"
>> +vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64
>> +vfio_load_state_device_data(const char *name, uint64_t data_offset, uint64_t data_size) " (%s) Offset 0x%"PRIx64" size 0x%"PRIx64
>