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Re: [PATCH] IOMMU and ATS not supported by vhost-user filesystem.
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH] IOMMU and ATS not supported by vhost-user filesystem. |
Date: |
Wed, 27 Jan 2021 16:34:23 +0000 |
User-agent: |
Mutt/1.14.6 (2020-07-11) |
* Leonardo Augusto Guimarães Garcia (lagarcia@linux.ibm.com) wrote:
> On 1/27/21 8:19 AM, Stefan Hajnoczi wrote:
> > On Tue, Jan 26, 2021 at 03:23:38PM -0300, lagarcia@linux.ibm.com wrote:
> > > From: Leonardo Garcia <lagarcia@br.ibm.com>
> > >
> > > Currently, as IOMMU and ATS are not supported, if a user mistakenly set
> > > any of them and tries to mount the vhost-user filesystem inside the
> > > guest, whenever the user tries to access the mount point, the system
> > > will hang forever.
> > >
> > > Signed-off-by: Leonardo Garcia <lagarcia@br.ibm.com>
> > > ---
> > > hw/virtio/vhost-user-fs-pci.c | 7 +++++++
> > > hw/virtio/vhost-user-fs.c | 5 +++++
> > > 2 files changed, 12 insertions(+)
> > >
> > > diff --git a/hw/virtio/vhost-user-fs-pci.c b/hw/virtio/vhost-user-fs-pci.c
> > > index 2ed8492b3f..564d1fd108 100644
> > > --- a/hw/virtio/vhost-user-fs-pci.c
> > > +++ b/hw/virtio/vhost-user-fs-pci.c
> > > @@ -11,6 +11,8 @@
> > > * top-level directory.
> > > */
> > > +#include "qemu/osdep.h"
> > > +#include "qapi/error.h"
> > > #include "qemu/osdep.h"
> > > #include "hw/qdev-properties.h"
> > > #include "hw/virtio/vhost-user-fs.h"
> > > @@ -45,6 +47,11 @@ static void vhost_user_fs_pci_realize(VirtIOPCIProxy
> > > *vpci_dev, Error **errp)
> > > vpci_dev->nvectors = dev->vdev.conf.num_request_queues + 2;
> > > }
> > > + if (vpci_dev->flags & VIRTIO_PCI_FLAG_ATS) {
> > > + error_setg(errp, "ATS is currently not supported with
> > > vhost-user-fs-pci");
> > > + return;
> > > + }
> > Why is this check needed in addition to VIRTIO_F_IOMMU_PLATFORM?
> >
> > What needs to be added to support ATS?
> >
> > > +
> > > qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
> > > }
> > > diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> > > index ac4fc34b36..914d68b3ee 100644
> > > --- a/hw/virtio/vhost-user-fs.c
> > > +++ b/hw/virtio/vhost-user-fs.c
> > > @@ -203,6 +203,11 @@ static void vuf_device_realize(DeviceState *dev,
> > > Error **errp)
> > > return;
> > > }
> > > + if (virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) {
> > > + error_setg(errp, "IOMMU is currently not supported with
> > > vhost-user-fs");
> > > + return;
> > > + }
> > > +
> > > if (!vhost_user_init(&fs->vhost_user, &fs->conf.chardev, errp)) {
> > I thought IOMMU support depends on the vhost-user device backend (e.g.
> > virtiofsd), so the vhost-user backend should participate in advertising
> > this feature.
> >
> > Perhaps the check should be:
> >
> > ret = vhost_dev_init(&fs->vhost_dev, &fs->vhost_user,
> > VHOST_BACKEND_TYPE_USER, 0);
> > if (ret < 0) {
> > error_setg_errno(errp, -ret, "vhost_dev_init failed");
> > goto err_virtio;
> > }
> > +
> > + if (virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM) &&
> > + !(fs->vhost_dev.hdev_features & (1ull << VIRTIO_F_IOMMU_PLATFORM)))
> > {
> > + error_setg(errp, "IOMMU is not supported by the vhost-user device
> > backend");
> > + goto err_iommu_needed;
> > + }
> >
> > Also, can this logic be made generic for all vhost-user devices? It's
> > not really specific to vhost-user-fs.
>
> Further analyzing this, on vhost-user.c, I see:
>
> Â Â Â Â Â Â Â if (virtio_has_feature(features, VIRTIO_F_IOMMU_PLATFORM) &&
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â !(virtio_has_feature(dev->protocol_features,
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VHOST_USER_PROTOCOL_F_SLAVE_REQ) &&
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â virtio_has_feature(dev->protocol_features,
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VHOST_USER_PROTOCOL_F_REPLY_ACK))) {
> Â Â Â Â Â Â Â Â Â Â Â error_report("IOMMU support requires reply-ack and "
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â "slave-req protocol
> features.");
> Â Â Â Â Â Â Â Â Â Â Â return -1;
> Â Â Â Â Â Â Â }
>
> This code was included by commit 6dcdd06. It included support for
> VIRTIO_F_IOMMU_PLATFORM with vhost_net devices. So, the restriction is not
> generic for all vhost-user devices.
That test is a slightly different test; that's checking that the
vhost-user device has two underlying features that are needed to make
iommu work; it's not a full test though; it doesn't actually check the
vhost-user device also wants to do iommu.
Dave
> Cheers,
>
> Leo
>
> >
> > Stefan
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
Re: [PATCH] IOMMU and ATS not supported by vhost-user filesystem., Laszlo Ersek, 2021/01/27
Re: [PATCH] IOMMU and ATS not supported by vhost-user filesystem., Leonardo Augusto Guimarães Garcia, 2021/01/28