Hi Eric,
> From: Eric Auger <eric.auger@xxxxxxxxxx>
> Sent: Thursday, April 6, 2023 5:47 PM
>
> Hi Yi,
>
> On 4/1/23 17:18, Yi Liu wrote:
> > This defines KVM_DEV_VFIO_FILE* and make alias with KVM_DEV_VFIO_GROUP*.
> > Old userspace uses KVM_DEV_VFIO_GROUP* works as well.
> >
> > Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> > Tested-by: Terrence Xu <terrence.xu@xxxxxxxxx>
> > Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Tested-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> > Tested-by: Yanting Jiang <yanting.jiang@xxxxxxxxx>
> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > ---
> > Documentation/virt/kvm/devices/vfio.rst | 53 +++++++++++++++++--------
> > include/uapi/linux/kvm.h | 16 ++++++--
> > virt/kvm/vfio.c | 16 ++++----
> > 3 files changed, 56 insertions(+), 29 deletions(-)
> >
> > diff --git a/Documentation/virt/kvm/devices/vfio.rst
> b/Documentation/virt/kvm/devices/vfio.rst
> > index 79b6811bb4f3..277d727ec1a2 100644
> > --- a/Documentation/virt/kvm/devices/vfio.rst
> > +++ b/Documentation/virt/kvm/devices/vfio.rst
> > @@ -9,24 +9,38 @@ Device types supported:
> > - KVM_DEV_TYPE_VFIO
> >
> > Only one VFIO instance may be created per VM. The created device
> > -tracks VFIO groups in use by the VM and features of those groups
> > -important to the correctness and acceleration of the VM. As groups
> > -are enabled and disabled for use by the VM, KVM should be updated
> > -about their presence. When registered with KVM, a reference to the
> > -VFIO-group is held by KVM.
> > +tracks VFIO files (group or device) in use by the VM and features
> > +of those groups/devices important to the correctness and acceleration
> > +of the VM. As groups/devices are enabled and disabled for use by the
> > +VM, KVM should be updated about their presence. When registered with
> > +KVM, a reference to the VFIO file is held by KVM.
> >
> > Groups:
> > - KVM_DEV_VFIO_GROUP
> > -
> > -KVM_DEV_VFIO_GROUP attributes:
> > - KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking
> > - kvm_device_attr.addr points to an int32_t file descriptor
> > - for the VFIO group.
> > - KVM_DEV_VFIO_GROUP_DEL: Remove a VFIO group from VFIO-KVM device
> tracking
> > - kvm_device_attr.addr points to an int32_t file descriptor
> > - for the VFIO group.
> > - KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
> > + KVM_DEV_VFIO_FILE
> > + alias: KVM_DEV_VFIO_GROUP
> > +
> > +KVM_DEV_VFIO_FILE attributes:
> > + KVM_DEV_VFIO_FILE_ADD: Add a VFIO file (group/device) to VFIO-KVM device
> > + tracking
> > +
> > + alias: KVM_DEV_VFIO_GROUP_ADD
> > +
> > + kvm_device_attr.addr points to an int32_t file descriptor for the
> > + VFIO file.
> > +
> > + KVM_DEV_VFIO_FILE_DEL: Remove a VFIO file (group/device) from VFIO-KVM
> > + device tracking
> > +
> > + alias: KVM_DEV_VFIO_GROUP_DEL
> > +
> > + kvm_device_attr.addr points to an int32_t file descriptor for the
> > + VFIO file.
> > +
> > + KVM_DEV_VFIO_FILE_SET_SPAPR_TCE: attaches a guest visible TCE table
> > allocated by sPAPR KVM.
> > +
> > + alias: KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE
> > +
> > kvm_device_attr.addr points to a struct::
> >
> > struct kvm_vfio_spapr_tce {
> > @@ -40,9 +54,14 @@ KVM_DEV_VFIO_GROUP attributes:
> > - @tablefd is a file descriptor for a TCE table allocated via
> > KVM_CREATE_SPAPR_TCE.
> >
> > + only accepts vfio group file as SPAPR has no iommufd support
> So then what is the point of introducing
>
> KVM_DEV_VFIO_FILE_SET_SPAPR_TCE at this stage?
the major reason is to make the naming aligned since this patch
names the groups as KVM_DEV_VFIO_FILE.
>
> I think would have separated the
>
> Groups:
> KVM_DEV_VFIO_FILE
> alias: KVM_DEV_VFIO_GROUP
>
> KVM_DEV_VFIO_FILE attributes:
> KVM_DEV_VFIO_FILE_ADD: Add a VFIO file (group/device) to VFIO-KVM device
> tracking
>
> kvm_device_attr.addr points to an int32_t file descriptor for the
> VFIO file.
>
> KVM_DEV_VFIO_FILE_DEL: Remove a VFIO file (group/device) from VFIO-KVM
> device tracking
>
> kvm_device_attr.addr points to an int32_t file descriptor for the
> VFIO file.
>
> KVM_DEV_VFIO_GROUP (legacy kvm device group restricted to the handling of VFIO
> group fd)
> KVM_DEV_VFIO_GROUP_ADD: same as KVM_DEV_VFIO_FILE_ADD for group fd only
> KVM_DEV_VFIO_GROUP_DEL: same as KVM_DEV_VFIO_FILE_DEL for group fd only
> KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
> allocated by sPAPR KVM.
> kvm_device_attr.addr points to a struct::
>
> struct kvm_vfio_spapr_tce {
> __s32 groupfd;
> __s32 tablefd;
> };
>
> where:
>
> - @groupfd is a file descriptor for a VFIO group;
> - @tablefd is a file descriptor for a TCE table allocated via
> KVM_CREATE_SPAPR_TCE.
hmmm, this way is clearer. I'd adopt it if it's acceptable.
>
> You don't say anything about potential restriction, ie. what if the user calls
> KVM_DEV_VFIO_FILE with device fds while it has been using legacy container/group
> API?
legacy container/group path cannot do it as the below enhancement.
User needs to call KVM_DEV_VFIO_FILE before open devices, so this
should happen before _GET_DEVICE_FD. So the legacy path can never
pass device fds in KVM_DEV_VFIO_FILE.
https://lore.kernel.org/kvm/20230327102059.333d6976.alex.williamson@xxxxxxxxxx/#t
> > -The GROUP_ADD operation above should be invoked prior to accessing the
> > +The FILE/GROUP_ADD operation above should be invoked prior to accessing the
> > device file descriptor via VFIO_GROUP_GET_DEVICE_FD in order to support
> > drivers which require a kvm pointer to be set in their .open_device()
> > -callback.
> > +callback. It is the same for device file descriptor via character device
> > +open which gets device access via VFIO_DEVICE_BIND_IOMMUFD. For such file
> > +descriptors, FILE_ADD should be invoked before VFIO_DEVICE_BIND_IOMMUFD
> > +to support the drivers mentioned in prior sentence as well.
just as here. This means device fds can only be passed with KVM_DEV_VFIO_FILE
in the cdev path.
Regards,
Yi Liu
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index d77aef872a0a..a8eeca70a498 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -1410,10 +1410,18 @@ struct kvm_device_attr {
> > __u64 addr; /* userspace address of attr data */
> > };
> >
> > -#define KVM_DEV_VFIO_GROUP 1
> > -#define KVM_DEV_VFIO_GROUP_ADD 1
> > -#define KVM_DEV_VFIO_GROUP_DEL 2
> > -#define KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE 3
> > +#define KVM_DEV_VFIO_FILE 1
> > +
> > +#define KVM_DEV_VFIO_FILE_ADD 1
> > +#define KVM_DEV_VFIO_FILE_DEL 2
> > +#define KVM_DEV_VFIO_FILE_SET_SPAPR_TCE 3
> > +
> > +/* KVM_DEV_VFIO_GROUP aliases are for compile time uapi compatibility */
> > +#define KVM_DEV_VFIO_GROUP KVM_DEV_VFIO_FILE
> > +
> > +#define KVM_DEV_VFIO_GROUP_ADD KVM_DEV_VFIO_FILE_ADD
> > +#define KVM_DEV_VFIO_GROUP_DEL KVM_DEV_VFIO_FILE_DEL
> > +#define KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE
> KVM_DEV_VFIO_FILE_SET_SPAPR_TCE
> >
> > enum kvm_device_type {
> > KVM_DEV_TYPE_FSL_MPIC_20 = 1,
> > diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> > index 857d6ba349e1..d869913baafd 100644
> > --- a/virt/kvm/vfio.c
> > +++ b/virt/kvm/vfio.c
> > @@ -286,18 +286,18 @@ static int kvm_vfio_set_file(struct kvm_device *dev, long
> attr,
> > int32_t fd;
> >
> > switch (attr) {
> > - case KVM_DEV_VFIO_GROUP_ADD:
> > + case KVM_DEV_VFIO_FILE_ADD:
> > if (get_user(fd, argp))
> > return -EFAULT;
> > return kvm_vfio_file_add(dev, fd);
> >
> > - case KVM_DEV_VFIO_GROUP_DEL:
> > + case KVM_DEV_VFIO_FILE_DEL:
> > if (get_user(fd, argp))
> > return -EFAULT;
> > return kvm_vfio_file_del(dev, fd);
> >
> > #ifdef CONFIG_SPAPR_TCE_IOMMU
> > - case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
> > + case KVM_DEV_VFIO_FILE_SET_SPAPR_TCE:
> > return kvm_vfio_file_set_spapr_tce(dev, arg);
> > #endif
> > }
> > @@ -309,7 +309,7 @@ static int kvm_vfio_set_attr(struct kvm_device *dev,
> > struct kvm_device_attr *attr)
> > {
> > switch (attr->group) {
> > - case KVM_DEV_VFIO_GROUP:
> > + case KVM_DEV_VFIO_FILE:
> > return kvm_vfio_set_file(dev, attr->attr,
> > u64_to_user_ptr(attr->addr));
> > }
> > @@ -321,12 +321,12 @@ static int kvm_vfio_has_attr(struct kvm_device *dev,
> > struct kvm_device_attr *attr)
> > {
> > switch (attr->group) {
> > - case KVM_DEV_VFIO_GROUP:
> > + case KVM_DEV_VFIO_FILE:
> > switch (attr->attr) {
> > - case KVM_DEV_VFIO_GROUP_ADD:
> > - case KVM_DEV_VFIO_GROUP_DEL:
> > + case KVM_DEV_VFIO_FILE_ADD:
> > + case KVM_DEV_VFIO_FILE_DEL:
> > #ifdef CONFIG_SPAPR_TCE_IOMMU
> > - case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
> > + case KVM_DEV_VFIO_FILE_SET_SPAPR_TCE:
> > #endif
> > return 0;
> > }
