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Subject: Re: [PATCH v10 3/5] hisi_acc_vfio_pci: register debugfs for hisilicon
 migration driver
To:     Jason Gunthorpe <jgg@nvidia.com>
CC:     <alex.williamson@redhat.com>,
        <shameerali.kolothum.thodi@huawei.com>,
        <jonathan.cameron@huawei.com>, <cohuck@redhat.com>,
        <linux-kernel@vger.kernel.org>, <linuxarm@openeuler.org>
References: <20230408074224.62608-1-liulongfang@huawei.com>
 <20230408074224.62608-4-liulongfang@huawei.com> <ZDlGC8SUXqKNmfSe@nvidia.com>
From:   liulongfang <liulongfang@huawei.com>
Message-ID: <ca592d60-9a5b-dec3-9565-76cd5c0740e0@huawei.com>
Date:   Fri, 21 Apr 2023 11:27:49 +0800
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On 2023/4/14 20:24, Jason Gunthorpe wrote:
> On Sat, Apr 08, 2023 at 03:42:22PM +0800, Longfang Liu wrote:
>> +static int hisi_acc_vf_debug_restore(struct seq_file *seq, void *data)
>> +{
>> +	struct device *vf_dev = seq->private;
>> +	struct vfio_pci_core_device *core_device = dev_get_drvdata(vf_dev);
>> +	struct vfio_device	*vdev = &core_device->vdev;
>> +	struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(vdev);
>> +	struct hisi_acc_vf_migration_file *migf = hisi_acc_vdev->debug_migf;
>> +	int ret;
>> +
>> +	ret = hisi_acc_vf_debug_check(seq, vdev);
>> +	if (ret)
>> +		goto restore_err;
>> +
>> +	ret = vf_qm_state_save(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		seq_printf(seq, "%s\n", "failed to save device data!");
>> +		goto restore_err;
>> +	}
>> +
>> +	ret = vf_qm_check_match(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		seq_printf(seq, "%s\n", "failed to match the VF!");
>> +		goto restore_err;
>> +	}
>> +
>> +	ret = vf_qm_load_data(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		seq_printf(seq, "%s\n", "failed to recover the VF!");
>> +		goto restore_err;
>> +	}
>> +
>> +	vf_qm_fun_reset(&hisi_acc_vdev->vf_qm);
>> +	seq_printf(seq, "%s\n", "successful to resume device data!");
>> +
>> +restore_err:
>> +	return 0;
>> +}
> 
> This is basically an in-kernel self test, it should be protected with
> some kind of VFIO selftest kconfig.
> 
As a debugfs function, its usage will be more flexible for users.

> Though, I wonder why we need it??? 
After a live migration error occurs. Through this debugfs function,
you can perform separate functional tests on the source and destination
to locate the cause of the error.

Can't you write a trivial userspace
> program under tools/testing to do this sequence with the ioctls?
>
Sorry, I still wish this feature was a simple debugfs feature.
If you want the userspace testing tool you mentioned,
you can try it on mlx5.

Thanks,
Longfang.
>> +static int hisi_acc_vf_debug_save(struct seq_file *seq, void *data)
>> +{
>> +	struct device *vf_dev = seq->private;
>> +	struct vfio_pci_core_device *core_device = dev_get_drvdata(vf_dev);
>> +	struct vfio_device	*vdev = &core_device->vdev;
>> +	struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(vdev);
>> +	struct hisi_acc_vf_migration_file *migf = hisi_acc_vdev->debug_migf;
>> +	int ret;
>> +
>> +	ret = hisi_acc_vf_debug_check(seq, vdev);
>> +	if (ret)
>> +		goto save_err;
>> +
>> +	ret = vf_qm_state_save(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		seq_printf(seq, "%s\n", "failed to save device data!");
>> +		goto save_err;
>> +	}
>> +	seq_printf(seq, "%s\n", "successful to save device data!");
>> +
>> +save_err:
>> +	return 0;
>> +}
> 
> Same kind of commen there, this is a selftest, why does it need a
> special kernel interface?
> 
> .. and so on..
> 
> I thought the non-selftesty bits were OK, maybe split the patch to
> match progress
> 
> Jason
> .
>