On Wed, Sep 15, 2021 at 01:28:47PM +0000, Shameerali Kolothum Thodi wrote: > > > > From: Jason Gunthorpe [mailto:jgg@xxxxxxxxxx] > > Sent: 15 September 2021 14:08 > > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > > Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > linux-crypto@xxxxxxxxxxxxxxx; alex.williamson@xxxxxxxxxx; > > mgurtovoy@xxxxxxxxxx; Linuxarm <linuxarm@xxxxxxxxxx>; liulongfang > > <liulongfang@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; > > Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>; Wangzhou (B) > > <wangzhou1@xxxxxxxxxxxxx> > > Subject: Re: [PATCH v3 6/6] hisi_acc_vfio_pci: Add support for VFIO live > > migration > > > > On Wed, Sep 15, 2021 at 10:50:37AM +0100, Shameer Kolothum wrote: > > > +/* > > > + * HiSilicon ACC VF dev MMIO space contains both the functional register > > > + * space and the migration control register space. We hide the migration > > > + * control space from the Guest. But to successfully complete the live > > > + * migration, we still need access to the functional MMIO space assigned > > > + * to the Guest. To avoid any potential security issues, we need to be > > > + * careful not to access this region while the Guest vCPUs are running. > > > + * > > > + * Hence check the device state before we map the region. > > > + */ > > > > The prior patch prevents mapping this area into the guest at all, > > right? > > That’s right. It will prevent Guest from mapping this area. > > > So why the comment and logic? If the MMIO area isn't mapped then there > > is nothing to do, right? > > > > The only risk is P2P transactions from devices in the same IOMMU > > group, and you might do well to mitigate that by asserting that the > > device is in a singleton IOMMU group? > > This was added as an extra protection. I will add the singleton check instead. > > > > +static int hisi_acc_vfio_pci_init(struct vfio_pci_core_device *vdev) > > > +{ > > > + struct acc_vf_migration *acc_vf_dev; > > > + struct pci_dev *pdev = vdev->pdev; > > > + struct pci_dev *pf_dev, *vf_dev; > > > + struct hisi_qm *pf_qm; > > > + int vf_id, ret; > > > + > > > + pf_dev = pdev->physfn; > > > + vf_dev = pdev; > > > + > > > + pf_qm = pci_get_drvdata(pf_dev); > > > + if (!pf_qm) { > > > + pr_err("HiSi ACC qm driver not loaded\n"); > > > + return -EINVAL; > > > + } > > > > Nope, this is locked wrong and has no lifetime management. > > Ok. Holding the device_lock() sufficient here? You can't hold a hisi_qm pointer with some kind of lifecycle management of that pointer. device_lock/etc is necessary to call pci_get_drvdata() Jason
