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[Xen-bugs] [Bug 1178] New: PCI BUS master DMA transfer continues after G

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Subject: [Xen-bugs] [Bug 1178] New: PCI BUS master DMA transfer continues after GuestOS crash
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Date: Mon, 25 Feb 2008 03:48:22 -0800
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           Summary: PCI BUS master DMA transfer continues after GuestOS
           Product: Xen
           Version: 3.0.1
          Platform: All
        OS/Version: Linux-2.6
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Hypervisor
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: gplcoder@xxxxxx

Both Dom0 und uDom using linux 2.6 (fc8).
pciback is used to allows access to PCI device.
In case guest OS crashes and terminated in the assigned to OS instance PCI
device performs BUS master transfer (from device to system memory) system
memory is overwritten and entire system receives unstable.

The solution is to stop PCI BUS master transfers for all assigned to guest OS
PCI devices if hypervisor detects guest OS crash or exit (like it done for

This can be done by disabling of the master capability in the device PCI
configuration space.

More elegant solution is possible for PCIe devices, but requires the disabling
of the master capability too.

Probably it is even better to disable the device (disable master, memory and
I/O in PCI configuration space) if device is assigned to pciback but no one
guestOS owns the device.

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