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

[Paolo Bonzini]

Il 10/10/2014 16:52, Paul Durrant ha scritto:
>> -----Original Message-----
>> From: Stefano Stabellini [mailto:address@hidden
>> Sent: 10 October 2014 15:40
>> To: Paul Durrant
>> Cc: address@hidden; address@hidden; 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 <address@hidden>
>>> Cc: Michael S. Tsirkin <address@hidden>
>>> Cc: Stefano Stabellini <address@hidden>
>>> Cc: Peter Maydell <address@hidden>
>>> Cc: Paolo Bonzini <address@hidden>
>>> Cc: Michael Tokarev <address@hidden>
>>> Cc: Stefan Hajnoczi <address@hidden>
>>> Cc: Stefan Weil <address@hidden>
>>> Cc: Andreas Faerber" <address@hidden>
>>> Cc: Thomas Huth <address@hidden>
>>> Cc: Peter Crosthwaite <address@hidden>
>>> Cc: Eduardo Habkost <address@hidden>
>>> Cc: Gerd Hoffmann <address@hidden>
>>> Cc: Alexey Kardashevskiy <address@hidden>
>>> Cc: Alexander Graf <address@hidden>
>>> ---
>>>  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