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

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Date:   Tue, 7 Feb 2023 03:36:44 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>
CC:     "cohuck@...hat.com" <cohuck@...hat.com>,
        "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>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "intel-gvt-dev@...ts.freedesktop.org" 
        <intel-gvt-dev@...ts.freedesktop.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>
Subject: RE: [PATCH v2 05/14] kvm/vfio: Accept vfio device file from userspace

> 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"

> -  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.

> +	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

> +	- 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

>  	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?

> +	   KVM_CREATE_SPAPR_TCE.
> +	- alias: KVM_DEV_VFIO_FILE_SET_SPAPR_TCE

GROUP