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Re: [Xen-devel] [v7][RFC][PATCH 04/13] hvmloader/util: get reserved device memory maps

>>> On 31.10.14 at 03:20, <tiejun.chen@xxxxxxxxx> wrote:
> On 2014/10/30 17:13, Jan Beulich wrote:
>>>>> On 30.10.14 at 06:55, <tiejun.chen@xxxxxxxxx> wrote:
>>> On 2014/10/29 17:05, Jan Beulich wrote:
>>>>>>> On 29.10.14 at 07:54, <tiejun.chen@xxxxxxxxx> wrote:
>>>>> Looks I can remove those stuff from util.h and just add 'extern' to them
>>>>> when we really need them.
>>>> Please stop thinking this way. Declarations for things defined in .c
>>>> files are to be present in headers, and the defining .c file has to
>>>> include that header (making sure declaration and definition are and
>>>> remain in sync). I hate having to again repeat my remark that you
>>>> shouldn't forget it's not application code that you're modifying.
>>>> Robust and maintainable code are a requirement in the hypervisor
>>>> (and, as said it being an extension of it, hvmloader). Which - just
>>>> to avoid any misunderstanding - isn't to say that this shouldn't also
>>>> apply to application code. It's just that in the hypervisor and kernel
>>>> (and certain other code system components) the consequences of
>>>> being lax are much more severe.
>>> Okay. But currently, the pci.c file already include 'util.h' and
>>> '<xen/memory.h>,
>>> #include "util.h"
>>> ...
>>> #include <xen/memory.h>
>>> We can't redefine struct xen_reserved_device_memory in util.h.
>> Redefine? I said forward declare.
> Seems we just need to declare hvm_get_reserved_device_memory_map() in 
> the head file, tools/firmware/hvmloader/util.h,
> unsigned int hvm_get_reserved_device_memory_map(void);

To me this looks very much like poor programming style, even if in
the context of hvmloader communicating information via global
variables rather than function arguments and return values is
generally possible.


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