From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 25332] When a VM is rebooted, assigned devices do not get RESET
...
Date: Mon, 15 Aug 2011 15:51:26 GMT
Message-ID: <201108151551.p7FFpQKu029015@demeter2.kernel.org>
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--- Comment #2 from Casey Leedom 2011-08-15 15:51=
:25 ---
This is in reference to the ability to map a PCI Device into a Virtual =
Machine
=E2=80=94 sometimes referred to as "PCI Pass Through." For Intel archi=
tectures, VT-d
provides some of the critical underlaying architectural support for rem=
apping
device DMA and interrupts. Other architectures supply similar technolo=
gy.
At issue here is that the KVM Support in the hypervisor kernel does not=
issue a
pci_reset_function() call against all such devices when a Virtual Machi=
ne
reboots. This means that the Virtual Machine finds the device in a non=
-clean
condition on reboot. It also means that any peer devices/services that=
the
device hardware may be attached to will continue to see the non-RESET s=
tate on
the other side of the device until a driver is loaded in the Virtual Ma=
chine to
manage the device. Thus, for instance, if a network adapter had brough=
t up a
link and then a reboot was done, the peer would continue to see a Link =
Up
condition until the Virtual Machine rebooted and a driver for the devic=
e was
loaded.
The above phenomenology doesn't match the way that a reboot would affec=
t a real
machine. For a real machine, part of the reboot cycle would involve al=
l
devices and buses getting RESET. We need the KVM Hipervisor support to=
do the
same thing.
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