From: Jason Gunthorpe <jgg@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
"cohuck@redhat.com" <cohuck@redhat.com>,
"mgurtovoy@nvidia.com" <mgurtovoy@nvidia.com>,
"yishaih@nvidia.com" <yishaih@nvidia.com>,
Linuxarm <linuxarm@huawei.com>,
liulongfang <liulongfang@huawei.com>,
"Zengtao (B)" <prime.zeng@hisilicon.com>,
Jonathan Cameron <jonathan.cameron@huawei.com>,
"Wangzhou (B)" <wangzhou1@hisilicon.com>
Subject: Re: [PATCH v6 09/10] hisi_acc_vfio_pci: Add support for VFIO live migration
Date: Mon, 28 Feb 2022 16:29:19 -0400 [thread overview]
Message-ID: <20220228202919.GP219866@nvidia.com> (raw)
In-Reply-To: <20220228131614.27ad37dc.alex.williamson@redhat.com>
On Mon, Feb 28, 2022 at 01:16:14PM -0700, Alex Williamson wrote:
> On Mon, 28 Feb 2022 14:05:20 -0400
> Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> > On Mon, Feb 28, 2022 at 06:01:44PM +0000, Shameerali Kolothum Thodi wrote:
> >
> > > +static long hisi_acc_vf_save_unl_ioctl(struct file *filp,
> > > + unsigned int cmd, unsigned long arg)
> > > +{
> > > + struct hisi_acc_vf_migration_file *migf = filp->private_data;
> > > + loff_t *pos = &filp->f_pos;
> > > + struct vfio_device_mig_precopy precopy;
> > > + unsigned long minsz;
> > > +
> > > + if (cmd != VFIO_DEVICE_MIG_PRECOPY)
> > > + return -EINVAL;
> >
> > ENOTTY
> >
> > > +
> > > + minsz = offsetofend(struct vfio_device_mig_precopy, dirty_bytes);
> > > +
> > > + if (copy_from_user(&precopy, (void __user *)arg, minsz))
> > > + return -EFAULT;
> > > + if (precopy.argsz < minsz)
> > > + return -EINVAL;
> > > +
> > > + mutex_lock(&migf->lock);
> > > + if (*pos > migf->total_length) {
> > > + mutex_unlock(&migf->lock);
> > > + return -EINVAL;
> > > + }
> > > +
> > > + precopy.dirty_bytes = 0;
> > > + precopy.initial_bytes = migf->total_length - *pos;
> > > + mutex_unlock(&migf->lock);
> > > + return copy_to_user((void __user *)arg, &precopy, minsz) ? -EFAULT : 0;
> > > +}
> >
> > Yes
> >
> > And I noticed this didn't include the ENOMSG handling, read() should
> > return ENOMSG when it reaches EOS for the pre-copy:
> >
> > + * During pre-copy the migration data FD has a temporary "end of stream" that is
> > + * reached when both initial_bytes and dirty_byte are zero. For instance, this
> > + * may indicate that the device is idle and not currently dirtying any internal
> > + * state. When read() is done on this temporary end of stream the kernel driver
> > + * should return ENOMSG from read(). Userspace can wait for more data (which may
> > + * never come) by using poll.
>
> I'm confused by your previous reply that the use of curr_state should
> be eliminated, isn't this ioctl only valid while the device is in the
> PRE_COPY or PRE_COPY_P2P states? Otherwise the STOP_COPY state would
> have some expectation to be able to use this ioctl for devices
> supporting PRE_COPY.
I think it is fine to keep working on stop copy, though the
implementation here isn't quite right for that..
if (migf->total_length > QM_MATCH_SIZE)
precopy.dirty_bytes = migf->total_length - QM_MATCH_SIZE - *pos;
else
precopy.dity_bytes = 0;
if (*pos < QM_MATCH_SIZE)
precopy.initial_bytes = QM_MATCH_SIZE - *pos;
else
precopy.initial_Bytes = 0;
Unless you think we should block it.
> I'd like to see the uapi clarify exactly what states allow this
> ioctl and define the behavior of the ioctl when transitioning out of
> those states with an open data_fd, ie. is it defined to return an
> -errno once in STOP_COPY? Thanks,
The ioctl is on the data_fd, so it should follow all the normal rules
of the data_fd just like read() - ie all ioctls/read/write fails when
teh state is moved outside one where the data_fd is valid.
That looks like another issue with the above, it doesn't chck
migf->disabled.
Should we add another sentence about this?
Jason
next prev parent reply other threads:[~2022-02-28 20:29 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-28 9:01 [PATCH v6 00/10] vfio/hisilicon: add ACC live migration driver Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 01/10] crypto: hisilicon/qm: Move the QM header to include/linux Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 02/10] crypto: hisilicon/qm: Move few definitions to common header Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 03/10] hisi_acc_qm: Move PCI device IDs " Shameer Kolothum
2022-02-28 17:33 ` Alex Williamson
2022-02-28 20:12 ` Bjorn Helgaas
2022-02-28 20:23 ` Alex Williamson
2022-02-28 20:55 ` Bjorn Helgaas
2022-02-28 9:01 ` [PATCH v6 04/10] hisi_acc_vfio_pci: add new vfio_pci driver for HiSilicon ACC devices Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 05/10] hisi_acc_vfio_pci: Restrict access to VF dev BAR2 migration region Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 06/10] hisi_acc_vfio_pci: Add helper to retrieve the struct pci_driver Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 07/10] vfio: Extend the device migration protocol with PRE_COPY Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 08/10] crypto: hisilicon/qm: Set the VF QM state register Shameer Kolothum
2022-02-28 9:01 ` [PATCH v6 09/10] hisi_acc_vfio_pci: Add support for VFIO live migration Shameer Kolothum
2022-02-28 14:57 ` Jason Gunthorpe
2022-02-28 18:01 ` Shameerali Kolothum Thodi
2022-02-28 18:05 ` Jason Gunthorpe
2022-02-28 20:16 ` Alex Williamson
2022-02-28 20:29 ` Jason Gunthorpe [this message]
2022-02-28 21:20 ` Alex Williamson
2022-02-28 23:47 ` Jason Gunthorpe
2022-03-01 4:41 ` Alex Williamson
2022-03-01 13:15 ` Jason Gunthorpe
2022-03-01 19:30 ` Alex Williamson
2022-03-01 20:39 ` Jason Gunthorpe
2022-03-01 22:44 ` Alex Williamson
2022-03-02 0:03 ` Jason Gunthorpe
2022-03-02 9:07 ` Shameerali Kolothum Thodi
2022-02-28 9:01 ` [PATCH v6 10/10] hisi_acc_vfio_pci: Use its own PCI reset_done error handler Shameer Kolothum
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