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usb not settled when udev rule triggered [solved]
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DaggyStyle
Watchman
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Joined: 22 Mar 2006
Posts: 5413

PostPosted: Sun Jan 06, 2019 5:37 pm    Post subject: usb not settled when udev rule triggered [solved] Reply with quote

Greetings,

I have a udev rule that triggers a script every add and remove, the script scans all running vms and see if they have that usb as guest passthrough and andle the attach or detach.
the detach work but the attach fails with the following error;
Code:
error: Failed to attach device from /dev/stdin
error: internal error: unable to execute QEMU command 'device_add': failed to find host usb device 1:13

some googling suggested the device didn't settled yet. how can I make sure that the device is settled before I pass it to the guest?
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Last edited by DaggyStyle on Wed Feb 06, 2019 8:31 pm; edited 1 time in total
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ribx
Apprentice
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Joined: 20 Nov 2003
Posts: 219
Location: germany

PostPosted: Mon Jan 07, 2019 12:09 am    Post subject: Reply with quote

You could either write a wrapper script, that waits for the device or maybe your udev rule could be altered to run at a time, when the device is settle. Please provide the udev rule and the command/script that attaches the VM's usb.
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DaggyStyle
Watchman
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Joined: 22 Mar 2006
Posts: 5413

PostPosted: Tue Jan 08, 2019 3:30 pm    Post subject: Reply with quote

here:
Code:

igor@utils_server:~$ cat /etc/udev/rules.d/90-usb-libvirt-hotplug.rules /usr/local/bin/libvirt_passthrough_hotplug.sh
ACTION=="add", SUBSYSTEMS=="usb", RUN+="/usr/local/bin/libvirt_passthrough_hotplug.sh"
ACTION=="remove", SUBSYSTEMS=="usb", RUN+="/usr/local/bin/libvirt_passthrough_hotplug.sh"
#!/bin/bash -x
exec 2>>/tmp/err.log

temp_xml_file="$(mktemp /tmp/vm_xml_dump.XXXXXX)"
cmd=

function error {
        echo "Error: $*"
        exit 1
}

function handle_vm_usb {
        local domain=$1
        local busnum="$(echo ${BUSNUM} | sed 's/^0\+//g')"
        local devnum="$(echo ${DEVNUM} | sed 's/^0\+//g')"

        virsh --connect qemu:///system "${cmd}" "${domain}" /dev/stdin << END
<hostdev mode='subsystem' type='usb'>
  <source>
   <address bus='${busnum}' device='${devnum}' />
  </source>
</hostdev>
END
}

function match_usb_ids {
        local domain="$1"
        local file="$2"
        local vid="$(grep vendor ${file} | sed 's/\//=/g' | cut -f 2 -d '=' | sed "s/'//g;s/^0x//g")"
        local did="$(grep product ${file} | sed 's/\//=/g' | cut -f 2 -d '=' | sed "s/'//g;s/^0x//g")"
        local ret_val=1

        if [ "${vid}" = "${ID_VENDOR_ID}" -a "${did}" = "${ID_MODEL_ID}" ]; then
                ret_val=0
                handle_vm_usb "${domain}"
        fi

        return ${ret_val}
}

function scan_vm {
        local vm_name="$1"

        virsh -c qemu:///system dumpxml ${vm_name} > ${temp_xml_file}
        for lineno in $(grep -n "<hostdev" ${temp_xml_file} | cut -f 1 -d : | sed 's/-$//g'); do
                local end_sec=$(cat -n ${temp_xml_file} | tail -n +${lineno} | grep "</hostdev>" | head -1 | awk '{print $1}')
                local type

                sed -n "${lineno},${end_sec}p;$((end_sec+1))q" ${temp_xml_file} > ${temp_xml_file}1
                type="$(head -1 ${temp_xml_file}1 | tr ' ' '\n' | grep type | cut -f 2 -d = | sed "s/'//g")"
                case ${type} in
                        usb)
                                match_usb_ids "${vm_name}" "${temp_xml_file}1"
                                if [ $? -eq 0 ]; then
                                        break
                                fi
                        ;;

                        *)
                                echo "unsupported type ${type}"
                        ;;
                esac

        done

        rm -rf ${temp_xml_file}*
}

if [ -z "${BUSNUM}" ]; then
        error BUSNUM env var not set
fi

if [ -z "${DEVNUM}" ]; then
        error DEVNUM env var not set
fi

if [ -z "${ID_VENDOR_ID}" ]; then
        error ID_VENDOR_ID env var not set
fi

if [ -z "${ID_MODEL_ID}" ]; then
        error ID_MODEL_ID env var not set
fi

case ${ACTION} in
        add)
                cmd='attach-device'
        ;;

        remove)
                cmd='detach-device'
        ;;

        *)
                error unsupported action "${ACTION}"
        ;;
esac

for vm in $(virsh -c qemu:///system list | grep running | awk '{print $2}'); do
        scan_vm "${vm}"
done

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Fitzcarraldo
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Joined: 30 Aug 2008
Posts: 1774
Location: United Kingdom

PostPosted: Wed Jan 09, 2019 4:24 am    Post subject: Reply with quote

I'm not sure, but if the USB devices are mass storage devices you could try reducing delay_use to zero:

Code:
echo 0 > /sys/module/usb_storage/parameters/delay_use


Quote:
usb-storage.delay_use=
                        [UMS] The delay in seconds before a new device is
                        scanned for Logical Units (default 1)

Ref. https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt
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DaggyStyle
Watchman
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Joined: 22 Mar 2006
Posts: 5413

PostPosted: Wed Jan 09, 2019 12:52 pm    Post subject: Reply with quote

the device in question is a usb tv tuner.

maybe the only way is to have a active thread that awaits for a signal and when the rule is triggered, it signals that thread if the input is valid.
the thread will wait for 5 secs and initiate the action.
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DaggyStyle
Watchman
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Joined: 22 Mar 2006
Posts: 5413

PostPosted: Wed Feb 06, 2019 8:31 pm    Post subject: Reply with quote

solved by pinging a daemon
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