Re: [Xen-devel] [PATCH] Xen: Use the ioreq-server API when available

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

Il 10/10/2014 16:52, Paul Durrant ha scritto:
>> -----Original Message-----
>> From: Stefano Stabellini [mailto:stefano.stabellini@xxxxxxxxxxxxx]
>> Sent: 10 October 2014 15:40
>> To: Paul Durrant
>> Cc: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx; Michael S.
>> Tsirkin; Stefano Stabellini; Peter Maydell; Paolo Bonzini; Michael Tokarev;
>> Stefan Hajnoczi; Stefan Weil; Andreas Faerber"; Thomas Huth; Peter
>> Crosthwaite; Eduardo Habkost; Gerd Hoffmann; Alexey Kardashevskiy;
>> Alexander Graf
>> Subject: Re: [PATCH] Xen: Use the ioreq-server API when available
>>
>> On Fri, 10 Oct 2014, Paul Durrant wrote:
>>> The ioreq-server API added to Xen 4.5 offers better security than
>>> the existing Xen/QEMU interface because the shared pages that are
>>> used to pass emulation request/results back and forth are removed
>>> from the guest's memory space before any requests are serviced.
>>> This prevents the guest from mapping these pages (they are in a
>>> well known location) and attempting to attack QEMU by synthesizing
>>> its own request structures. Hence, this patch modifies configure
>>> to detect whether the API is available, and adds the necessary
>>> code to use the API if it is.
>>>
>>> The ioreq-server API does require that PCI device models explicitly
>>> register with Xen for config space accesses, so to use the API the
>>> code in xen-hvm.c needs to be informed as PCI devices are added or
>>> removed from PCI buses. This patch therefore also adds a PCI bus
>>> listener interface akin to the memory listener interface to fulfil
>>> this need.
>>>
>>> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
>>> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
>>> Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>>> Cc: Peter Maydell <peter.maydell@xxxxxxxxxx>
>>> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>>> Cc: Michael Tokarev <mjt@xxxxxxxxxx>
>>> Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
>>> Cc: Stefan Weil <sw@xxxxxxxxxxx>
>>> Cc: Andreas Faerber" <afaerber@xxxxxxx>
>>> Cc: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx>
>>> Cc: Peter Crosthwaite <peter.crosthwaite@xxxxxxxxxx>
>>> Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
>>> Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
>>> Cc: Alexey Kardashevskiy <aik@xxxxxxxxx>
>>> Cc: Alexander Graf <agraf@xxxxxxx>
>>> ---
>>>  configure               |   29 ++++++
>>>  hw/pci/pci.c            |   65 ++++++++++++
>>>  include/hw/pci/pci.h    |    9 ++
>>>  include/qemu/typedefs.h |    1 +
>>>  trace-events            |    8 ++
>>>  xen-hvm.c               |  251
>> +++++++++++++++++++++++++++++++++++++++++++----
>>>  6 files changed, 345 insertions(+), 18 deletions(-)
>>
>> Please split this patch into two: one to introduce the PCI listener
>> stuff and another for the Xen specific changes.
>>
> 
> Originally it was, but I was uneasy about introducing an interface with no 
> consumers. Is that generally acceptable?

It is the suggested way as long as the two patches are part of the same
series.

Paolo

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