Re: [Xen-devel] [PATCH v3 1/2] Differentiate IO/mem resources tracked by ioreq server

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 10/08/15 09:33, Paul Durrant wrote:
>> -----Original Message-----
>> From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx]
>> Sent: 10 August 2015 09:26
>> To: Yu Zhang
>> Cc: xen-devel@xxxxxxxxxxxxx; Paul Durrant; Ian Jackson; Stefano Stabellini; 
>> Ian
>> Campbell; Wei Liu; Keir (Xen.org); jbeulich@xxxxxxxx; Andrew Cooper;
>> Kevin Tian; zhiyuan.lv@xxxxxxxxx
>> Subject: Re: [PATCH v3 1/2] Differentiate IO/mem resources tracked by ioreq
>> server
>>
>> On Mon, Aug 10, 2015 at 11:33:40AM +0800, Yu Zhang wrote:
>>> Currently in ioreq server, guest write-protected ram pages are
>>> tracked in the same rangeset with device mmio resources. Yet
>>> unlike device mmio, which can be in big chunks, the guest write-
>>> protected pages may be discrete ranges with 4K bytes each.
>>>
>>> This patch uses a seperate rangeset for the guest ram pages.
>>> And a new ioreq type, IOREQ_TYPE_MEM, is defined.
>>>
>>> Note: Previously, a new hypercall or subop was suggested to map
>>> write-protected pages into ioreq server. However, it turned out
>>> handler of this new hypercall would be almost the same with the
>>> existing pair - HVMOP_[un]map_io_range_to_ioreq_server, and there's
>>> already a type parameter in this hypercall. So no new hypercall
>>> defined, only a new type is introduced.
>>>
>>> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
>>> ---
>>>  tools/libxc/include/xenctrl.h    | 39 +++++++++++++++++++++++---
>>>  tools/libxc/xc_domain.c          | 59
>> ++++++++++++++++++++++++++++++++++++++--
>>
>> FWIW the hypercall wrappers look correct to me.
>>
>>> diff --git a/xen/include/public/hvm/hvm_op.h
>> b/xen/include/public/hvm/hvm_op.h
>>> index 014546a..9106cb9 100644
>>> --- a/xen/include/public/hvm/hvm_op.h
>>> +++ b/xen/include/public/hvm/hvm_op.h
>>> @@ -329,8 +329,9 @@ struct xen_hvm_io_range {
>>>      ioservid_t id;               /* IN - server id */
>>>      uint32_t type;               /* IN - type of range */
>>>  # define HVMOP_IO_RANGE_PORT   0 /* I/O port range */
>>> -# define HVMOP_IO_RANGE_MEMORY 1 /* MMIO range */
>>> +# define HVMOP_IO_RANGE_MMIO   1 /* MMIO range */
>>>  # define HVMOP_IO_RANGE_PCI    2 /* PCI segment/bus/dev/func range
>> */
>>> +# define HVMOP_IO_RANGE_MEMORY 3 /* MEMORY range */
>> This looks problematic. Maybe you can get away with this because this is
>> a toolstack-only interface?
>>
> Indeed, the old name is a bit problematic. Presumably re-use like this would 
> require an interface version change and some if-defery.

I assume it is an interface used by qemu, so this patch in its currently
state will break things.

~Andrew

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