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<p>If VirtualBox causes a BSOD regardless of whether VT-x has been
grabbed by Hyper-V or any other program, it should be considered a
bug.</p>
<p>If VirtualBox is merely refusing to start the VM in hardware
virtualized mode, then that's normal and that's not something we
can do anything about until Microsoft changes Hyper-V to
relinquish VT-x when it's not being used (which I suspect isn't
simple for them to do, as Hyper-V is probably a "type 1" and it
can't do that without disabling Hyper-V altogether and doing a
reboot of the system).</p>
<p>VirtualBox already plays nice on Windows by default[1], by only
turning on VT-x when executing guest code and switching VT-x off
when VirtualBox gets back to executing host-context code. This way
when a VirtualBox virtual-CPU thread isn't executing guest code
anyone is free to use VT-x.</p>
<p>Regards,</p>
<p>As for running 32-bit VMs without VT-x that really should work.
What error are you getting in this case? Could you attach the
VBox.log for the VM in question?<br>
</p>
<p>Ram.</p>
<p>[1] -- This can be seen by checking the output of VBoxManage list
systemproperties and looking at "Exclusive HW virtualization" (it
should be "on" on Windows hosts by default).</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 03/21/2017 03:47 PM, Mikhail Kovalev
wrote:<br>
</div>
<blockquote
cite="mid:CAB8+GYBhcXaKviXXyWxRTmp8SprXUzYDwTBfvq4oqd7Dh2BSxQ@mail.gmail.com"
type="cite">
<div dir="ltr">Hello,
<div><br>
</div>
<div>in the current state VirtualBox doesn't work on Win10 in
case if Hyper-V is enabled. I do understand that VT-x is not
available for VirtualBox in that case, but at least the 32-bit
VMs could work without VT-x. </div>
<div>In the bug ticket #15780, Frank wrote </div>
<div><br>
</div>
<div>"<a moz-do-not-send="true" class="inbox-inbox-wiki"
href="https://www.virtualbox.org/wiki/VirtualBox"
style="font-size:13px;text-decoration:none;color:rgb(0,0,192);border-bottom:none;font-family:verdana,"bitstream
vera sans",sans-serif">VirtualBox</a><span
style="font-size:13px;font-family:verdana,"bitstream
vera sans",sans-serif"><span
class="inbox-inbox-Apple-converted-space"> </span>is
trying to change the CR4 value but the host crashes try to
do so. The reason is most likely that Hyper-V is active.
Please try to disable Hyper-V". </span></div>
<div><span
style="font-size:13px;font-family:verdana,"bitstream
vera sans",sans-serif"><br>
</span></div>
<div><span
style="font-size:13px;font-family:verdana,"bitstream
vera sans",sans-serif">So this is a Hyper-V bug and
nothing can be done on the VirtualBox side to fix this? Or
is there a chance that this problem will get fixed in the
upcoming releases of VirtualBox?</span></div>
<div><span
style="font-size:13px;font-family:verdana,"bitstream
vera sans",sans-serif"><br>
</span></div>
<div><span
style="font-size:13px;font-family:verdana,"bitstream
vera sans",sans-serif">If I additionally enable the
CredentialsGuard with Virtualization Based Protection for
Code Integrity (without activating Code Integrity Policies)
on Win 10, then VirtualBox crashes even earlier</span><font
face="verdana, sans-serif"> with "Failed to load VMMR0.r0".
I guess this is a different issue and it's unrelated to the
BSOD. I would create a bug ticket for that, but it probably
doesn't make much sense currently because of the BSOD
problem. </font></div>
<div><font face="verdana, sans-serif"><br>
</font></div>
<div><font face="verdana, sans-serif"><br>
</font></div>
<div><font face="verdana, sans-serif">Thnx & best regards,</font></div>
<div><font face="verdana, sans-serif">Mikhail</font></div>
</div>
<br>
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<br>
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</pre>
</blockquote>
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