Re: [PATCH RFC 1/1] allow to specify additional config data

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 7 Jun 2019 14:26:13 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> On 6/6/19 12:15 PM, Alex Williamson wrote:
> > On Thu, 6 Jun 2019 09:32:24 -0600
> > Alex Williamson <alex.williamson@redhat.com> wrote:
> >   
> >> On Thu,  6 Jun 2019 16:44:17 +0200
> >> Cornelia Huck <cohuck@redhat.com> wrote:
> >>  
> >>> Add a rough implementation for vfio-ap.
> >>>
> >>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> >>> ---
> >>>   mdevctl.libexec | 25 ++++++++++++++++++++++
> >>>   mdevctl.sbin    | 56 ++++++++++++++++++++++++++++++++++++++++++++++++-
> >>>   2 files changed, 80 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/mdevctl.libexec b/mdevctl.libexec
> >>> index 804166b5086d..cc0546142924 100755
> >>> --- a/mdevctl.libexec
> >>> +++ b/mdevctl.libexec
> >>> @@ -54,6 +54,19 @@ wait_for_supported_types () {
> >>>       fi
> >>>   }
> >>>   
> >>> +# configure vfio-ap devices <config entry> <matrix attribute>
> >>> +configure_ap_devices() {
> >>> +    list="`echo "${config[$1]}" | sed 's/,/ /'`"
> >>> +    [ -z "$list" ] && return
> >>> +    for a in $list; do
> >>> +        echo "$a" > "$supported_types/${config[mdev_type]}/devices/$uuid/$2"
> >>> +        if [ $? -ne 0 ]; then
> >>> +            echo "Error writing '$a' to '$uuid/$2'" >&2
> >>> +            exit 1
> >>> +        fi
> >>> +    done
> >>> +}
> >>> +
> >>>   case ${1} in
> >>>       start-mdev|stop-mdev)
> >>>           if [ $# -ne 2 ]; then
> >>> @@ -148,6 +161,18 @@ case ${cmd} in
> >>>               echo "Error creating mdev type ${config[mdev_type]} on $parent" >&2
> >>>               exit 1
> >>>           fi
> >>> +
> >>> +        # some types may specify additional config data
> >>> +        case ${config[mdev_type]} in
> >>> +            vfio_ap-passthrough)  
> >>
> >> I think this could have some application beyond ap too, I know NVIDIA
> >> GRID vGPUs do have some controls under the vendor hierarchy of the
> >> device, ex. setting the frame rate limiter.  The implementation here is
> >> a bit rigid, we know a specific protocol for a specific mdev type, but
> >> for supporting arbitrary vendor options we'd really just want to try to
> >> apply whatever options are provided.  If we didn't care about ordering,
> >> we could just look for keys for every file in the device's immediate
> >> sysfs hierarchy and apply any value we find, independent of the
> >> mdev_type, ex. intel_vgpu/foo=bar  Thanks,  
> > 
> > For example:
> > 
> > for key in find -P $mdev_base/$uuid/ \( -path
> > "$mdev_base/$uuid/power/*" -o -path $mdev_base/$uuid/uevent -o -path $mdev_base/$uuid/remove \) -prune -o -type f -print | sed -e "s|$mdev_base/$uuid/||g"); do
> >    [ -z ${config[$key]} ] && continue
> >    ... parse value(s) and iteratively apply to key
> > done
> > 
> > The find is a little ugly to exclude stuff, maybe we just let people do
> > screwy stuff like specify remove=1 in their config.  Also need to think
> > about whether we're imposing a delimiter to apply multiple values to a
> > key that conflicts with the attribute usage.  Thanks,
> > 
> > Alex  
> 
> I like the idea of looking for files in the device's immediate sysfs
> hierarchy, but maybe the find could exclude attributes that are
> not vendor defined.

How would we know what attributes are vendor defined?  The above `find`
strips out the power, uevent, and remove attributes, which for GVT-g
leaves only the vendor defined attributes[1], but I don't know how to
instead do a positive match of the vendor attributes without
unmaintainable lookup tables.  This starts to get into the question of
how much do we want to (or need to) protect the user from themselves.
If we let the user specify a key=value of remove=1 and the device
immediately disappears, is that a bug or a feature?  Thanks,

Alex

[1] GVT-g doesn't actually have an writable attributes, so we'd also
minimally want to add a test to skip read-only attributes.

> >>> +                configure_ap_devices ap_adapters assign_adapter
> >>> +                configure_ap_devices ap_domains assign_domain
> >>> +                configure_ap_devices ap_control_domains assign_control_domain
> >>> +                # TODO: is assigning idempotent? Should we unwind on error?
> >>> +                ;;
> >>> +            *)
> >>> +                ;;
> >>> +        esac
> >>>           ;;
> >>>   
> >>>       add-mdev)
> >>> diff --git a/mdevctl.sbin b/mdevctl.sbin
> >>> index 276cf6ddc817..eb5ee0091879 100755
> >>> --- a/mdevctl.sbin
> >>> +++ b/mdevctl.sbin
> >>> @@ -33,6 +33,8 @@ usage() {
> >>>       echo "set-start <mdev UUID>: change mdev start policy, if no option specified," >&2
> >>>       echo "                       system default policy is used" >&2
> >>>       echo "                       options: [--auto] [--manual]" >&2
> >>> +    echo "set-additional-config <mdev UUID> {fmt...}: supply additional configuration" >&2
> >>> +    echo "show-additional-config-format <mdev UUiD>:  prints the format expected by the device" >&2
> >>>       echo "list-all: list all possible mdev types supported in the system" >&2
> >>>       echo "list-available: list all mdev types currently available" >&2
> >>>       echo "list-mdevs: list currently configured mdevs" >&2
> >>> @@ -48,7 +50,7 @@ while (($# > 0)); do
> >>>           --manual)
> >>>               config[start]=manual
> >>>               ;;
> >>> -        start-mdev|stop-mdev|remove-mdev|set-start)
> >>> +        start-mdev|stop-mdev|remove-mdev|set-start|show-additional-config-format)
> >>>               [ $# -ne 2 ] && usage
> >>>               cmd=$1
> >>>               uuid=$2
> >>> @@ -67,6 +69,14 @@ while (($# > 0)); do
> >>>               cmd=$1
> >>>               break
> >>>               ;;
> >>> +        set-additional-config)
> >>> +            [ $# -le 2 ] && usage
> >>> +            cmd=$1
> >>> +            uuid=$2
> >>> +            shift 2
> >>> +            addtl_config="$*"
> >>> +            break
> >>> +            ;;
> >>>           *)
> >>>               usage
> >>>               ;;
> >>> @@ -114,6 +124,50 @@ case ${cmd} in
> >>>           fi
> >>>           ;;
> >>>   
> >>> +    set-additional-config)
> >>> +        file=$(find $persist_base -name $uuid -type f)
> >>> +        if [ -w "$file" ]; then
> >>> +            read_config "$file"
> >>> +            if [ ${config[start]} == "auto" ]; then
> >>> +                systemctl stop mdev@$uuid.service
> >>> +            fi
> >>> +            # FIXME: validate input!
> >>> +            for i in $addtl_config; do
> >>> +                key="`echo "$i" | cut -d '=' -f 1`"
> >>> +                value="`echo "$i" | cut -d '=' -f 2-`"
> >>> +                if grep -q ^$key $file; then
> >>> +                    if [ -z "$value" ]; then
> >>> +                        sed -i "s/^$key=.*//g" $file
> >>> +                    else
> >>> +                        sed -i "s/^$key=.*/$key=$value/g" $file
> >>> +                    fi
> >>> +                else
> >>> +                    echo "$i" >> "$file"
> >>> +                fi
> >>> +            done
> >>> +            if [ ${config[start]} == "auto" ]; then
> >>> +                systemctl start mdev@$uuid.service
> >>> +            fi
> >>> +        else
> >>> +            exit 1
> >>> +        fi
> >>> +        ;;
> >>> +
> >>> +    show-additional-config-format)
> >>> +        file=$(find $persist_base -name $uuid -type f)
> >>> +        read_config "$file"
> >>> +        case ${config[mdev_type]} in
> >>> +            vfio_ap-passthrough)
> >>> +                echo "ap_adapters=<comma-separated list of adapters>"
> >>> +                echo "ap_domains=<comma-separated list of domains>"
> >>> +                echo "ap_control_domains=<comma-separated list of control domains>"
> >>> +                ;;
> >>> +            *)
> >>> +                echo "no additional configuration defined"
> >>> +                ;;
> >>> +        esac
> >>> +        ;;
> >>> +
> >>>       list-mdevs)
> >>>           for mdev in $(find $mdev_base/ -maxdepth 1 -mindepth 1 -type l); do
> >>>               uuid=$(basename $mdev)  
> >>  
> >   
>