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Tsirkin" To: Steve Sistare Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jason Wang , Si-Wei Liu , Eugenio Perez Martin , Xuan Zhuo , Dragos Tatulea Subject: Re: [PATCH V2 3/7] vhost-vdpa: VHOST_NEW_OWNER Message-ID: <20240715050637-mutt-send-email-mst@kernel.org> References: <1720790333-456232-1-git-send-email-steven.sistare@oracle.com> <1720790333-456232-4-git-send-email-steven.sistare@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1720790333-456232-4-git-send-email-steven.sistare@oracle.com> On Fri, Jul 12, 2024 at 06:18:49AM -0700, Steve Sistare wrote: > Add an ioctl to transfer file descriptor ownership and pinned memory > accounting from one process to another. > > This is more efficient than VHOST_RESET_OWNER followed by VHOST_SET_OWNER, > as that would unpin all physical pages, requiring them to be repinned in > the new process. That would cost multiple seconds for large memories, and > be incurred during a virtual machine's pause time during live update. > > Signed-off-by: Steve Sistare Please, we just need to switch to use iommufd for pinning. Piling up all these hacks gets us nowhere. > --- > drivers/vhost/vdpa.c | 41 ++++++++++++++++++++++++++++++++++++++ > drivers/vhost/vhost.c | 15 ++++++++++++++ > drivers/vhost/vhost.h | 1 + > include/uapi/linux/vhost.h | 10 ++++++++++ > 4 files changed, 67 insertions(+) > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > index b49e5831b3f0..5cf55ca4ec02 100644 > --- a/drivers/vhost/vdpa.c > +++ b/drivers/vhost/vdpa.c > @@ -632,6 +632,44 @@ static long vhost_vdpa_resume(struct vhost_vdpa *v) > return ret; > } > > +static long vhost_vdpa_new_owner(struct vhost_vdpa *v) > +{ > + int r; > + struct vhost_dev *vdev = &v->vdev; > + struct mm_struct *mm_old = vdev->mm; > + struct mm_struct *mm_new = current->mm; > + long pinned_vm = v->pinned_vm; > + unsigned long lock_limit = PFN_DOWN(rlimit(RLIMIT_MEMLOCK)); > + > + if (!mm_old) > + return -EINVAL; > + mmgrab(mm_old); > + > + if (!v->vdpa->use_va && > + pinned_vm + atomic64_read(&mm_new->pinned_vm) > lock_limit) { > + r = -ENOMEM; > + goto out; > + } > + r = vhost_vdpa_bind_mm(v, mm_new); > + if (r) > + goto out; > + > + r = vhost_dev_new_owner(vdev); > + if (r) { > + vhost_vdpa_bind_mm(v, mm_old); > + goto out; > + } > + > + if (!v->vdpa->use_va) { > + atomic64_sub(pinned_vm, &mm_old->pinned_vm); > + atomic64_add(pinned_vm, &mm_new->pinned_vm); > + } > + > +out: > + mmdrop(mm_old); > + return r; > +} > + > static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd, > void __user *argp) > { > @@ -876,6 +914,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep, > case VHOST_VDPA_RESUME: > r = vhost_vdpa_resume(v); > break; > + case VHOST_NEW_OWNER: > + r = vhost_vdpa_new_owner(v); > + break; > default: > r = vhost_dev_ioctl(&v->vdev, cmd, argp); > if (r == -ENOIOCTLCMD) > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index b60955682474..ab40ae50552f 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -963,6 +963,21 @@ long vhost_dev_set_owner(struct vhost_dev *dev) > } > EXPORT_SYMBOL_GPL(vhost_dev_set_owner); > > +/* Caller should have device mutex */ > +long vhost_dev_new_owner(struct vhost_dev *dev) > +{ > + if (dev->mm == current->mm) > + return -EBUSY; > + > + if (!vhost_dev_has_owner(dev)) > + return -EINVAL; > + > + vhost_detach_mm(dev); > + vhost_attach_mm(dev); > + return 0; > +} > +EXPORT_SYMBOL_GPL(vhost_dev_new_owner); > + > static struct vhost_iotlb *iotlb_alloc(void) > { > return vhost_iotlb_alloc(max_iotlb_entries, > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index bb75a292d50c..8b2018bb02b1 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -187,6 +187,7 @@ void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, > int (*msg_handler)(struct vhost_dev *dev, u32 asid, > struct vhost_iotlb_msg *msg)); > long vhost_dev_set_owner(struct vhost_dev *dev); > +long vhost_dev_new_owner(struct vhost_dev *dev); > bool vhost_dev_has_owner(struct vhost_dev *dev); > long vhost_dev_check_owner(struct vhost_dev *); > struct vhost_iotlb *vhost_dev_reset_owner_prepare(void); > diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h > index b95dd84eef2d..543d0e3434c3 100644 > --- a/include/uapi/linux/vhost.h > +++ b/include/uapi/linux/vhost.h > @@ -123,6 +123,16 @@ > #define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64) > #define VHOST_GET_BACKEND_FEATURES _IOR(VHOST_VIRTIO, 0x26, __u64) > > +/* Set current process as the new owner of this file descriptor. The fd must > + * already be owned, via a prior call to VHOST_SET_OWNER. The pinned memory > + * count is transferred from the previous to the new owner. > + * Errors: > + * EINVAL: not owned > + * EBUSY: caller is already the owner > + * ENOMEM: RLIMIT_MEMLOCK exceeded > + */ > +#define VHOST_NEW_OWNER _IO(VHOST_VIRTIO, 0x27) > + > /* VHOST_NET specific defines */ > > /* Attach virtio net ring to a raw socket, or tap device. > -- > 2.39.3