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<p class="MsoNormal">We implemented an virt IO port for printing channel. It works without any problem if Qemu command options specify our printing device.<o:p></o:p></p>
<p class="MsoNormal">However, we found a bug in virtio serial driver when a VM is launched without specifying the “printing device” from the qemu command line.<o:p></o:p></p>
<p class="MsoNormal">In this case, mouse click does not work and no any key can be typed from keyboard.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In application(vdservice), it simply calls the following API to open the underline device.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:細明體"> _handle = CreateFile(DeviceName, GENERIC_READ | GENERIC_WRITE , 0, NULL,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:細明體"> OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:細明體">
<span style="color:blue">if</span> (_handle == INVALID_HANDLE_VALUE) {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:細明體"> vd_printf(<span style="color:#A31515">"CreateFile() %ls failed: %lu"</span>, DeviceName, GetLastError());<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:細明體">
<span style="color:blue">return</span> <span style="color:blue">false</span>;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:細明體"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:細明體"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:細明體">For working case, virioserial driver shows that both
</span><span style="font-size:9.0pt;font-family:"Times New Roman","serif"">“</span>com.redhat.spice.0” and “com.redhat.print.0” are opened.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">00000001 0.00000000 ==>VIOSerialPortCreate Port id = 1
<o:p></o:p></p>
<p class="MsoNormal">00000002 0.00001717 Port Name =com.redhat.spice.0
<o:p></o:p></p>
<p class="MsoNormal">………………………………….<o:p></o:p></p>
<p class="MsoNormal">00000107 0.00481843 ==>VIOSerialPortCreate Port id = 2
<o:p></o:p></p>
<p class="MsoNormal">00000108 0.00483288 Port Name =com.redhat.print.0
<o:p></o:p></p>
<p class="MsoNormal">00000109 0.00484705 No more buffers in queue: last_used_idx 0 vring.used->idx 0<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For the failure case, “<span style="font-size:9.0pt;font-family:細明體">CreateFile</span><span style="font-size:9.0pt;font-family:"Times New Roman","serif"">”</span><span style="font-size:9.0pt;font-family:細明體"> fails because it cannot open
</span><span style="font-size:9.0pt;font-family:"Times New Roman","serif"">“</span>com.redhat.print.0” device. But trace message of
<span style="font-size:9.0pt;font-family:細明體">virioserial driver only shows that </span>
<span style="font-size:9.0pt;font-family:"Times New Roman","serif"">“</span>com.redhat.spice.0” is opened.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If <span style="font-size:9.0pt;font-family:細明體">virioserial is not touched for
</span>“com.redhat.print.0” device, why it affects the “com.redhat.spice.0” device?<o:p></o:p></p>
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