linux-kernel - RE: [PATCH v2 05/14] kvm/vfio: Accept vfio device file from userspace

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Message-ID: <DS0PR11MB75291AF21AD96162E8099E84C3DB9@DS0PR11MB7529.namprd11.prod.outlook.com>
Date:   Tue, 7 Feb 2023 08:39:27 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>
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        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
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        <shameerali.kolothum.thodi@...wei.com>,
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Subject: RE: [PATCH v2 05/14] kvm/vfio: Accept vfio device file from userspace

> From: Tian, Kevin <kevin.tian@...el.com>
> Sent: Tuesday, February 7, 2023 11:37 AM
>
> > From: Liu, Yi L <yi.l.liu@...el.com>
> > Sent: Monday, February 6, 2023 5:05 PM
> >
> > This defines KVM_DEV_VFIO_FILE* and make alias with
> > KVM_DEV_VFIO_GROUP*.
> > Old userspace uses KVM_DEV_VFIO_GROUP* works as well.
> >
> > Signed-off-by: Yi Liu <yi.l.liu@...el.com>
> > ---
> >  Documentation/virt/kvm/devices/vfio.rst | 40 ++++++++++++++----------
> -
> >  include/uapi/linux/kvm.h                | 16 +++++++---
> >  virt/kvm/vfio.c                         | 16 +++++-----
> >  3 files changed, 42 insertions(+), 30 deletions(-)
> >
> > diff --git a/Documentation/virt/kvm/devices/vfio.rst
> > b/Documentation/virt/kvm/devices/vfio.rst
> > index 2d20dc561069..7f84ec26ca4a 100644
> > --- a/Documentation/virt/kvm/devices/vfio.rst
> > +++ b/Documentation/virt/kvm/devices/vfio.rst
> > @@ -9,23 +9,26 @@ 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:
> 
> "Files"

It should be "Groups" 😊 Here "Groups" means subcmd 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 kvm_device_attr.addr points to an int32_t file descriptor
> 
> "... device tracking" and "kvm_device.attr.addr points to..." are two
> sentences. They are deliberately arranged to be in different lines.

Oh, yes.

> > +	for the VFIO file.
> > +	- alias: KVM_DEV_VFIO_GROUP_ADD
> > +  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.
> 
> ditto

Will convert.

> 
> > +	- alias: KVM_DEV_VFIO_GROUP_DEL
> > +  KVM_DEV_VFIO_FILE_SET_SPAPR_TCE: attaches a guest visible TCE
> table
> >  	allocated by sPAPR KVM.
> 
> somehow here it should emphasize that the file can only be group

Yes.

> >  	kvm_device_attr.addr points to a struct::
> >
> > @@ -36,6 +39,7 @@ KVM_DEV_VFIO_GROUP attributes:
> >
> >  	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.
> > +	*) @groupfd is a file descriptor for a VFIO group;
> > +	*) @tablefd is a file descriptor for a TCE table allocated via
> 
> why changing above two lines?

this is due to changing "-" to be "*)" as subbullet as below need
to add alias.

> > +	   KVM_CREATE_SPAPR_TCE.
> > +	- alias: KVM_DEV_VFIO_FILE_SET_SPAPR_TCE
> 
> GROUP

Yes.

Regards,
Yi Liu