[vbox-dev] Opportunity to significantly shrink the vboxsf Linux driver

Larry Finger Larry.Finger at lwfinger.net
Mon Jul 10 19:37:22 UTC 2017

On 07/10/2017 10:12 AM, Michael Thayer wrote:
> Hello Hans,
> 10.07.2017 12:29, Hans de Goede wrote:
>> Hi,
>> On 10-07-17 12:08, Hans de Goede wrote:
>>> Hi all,
>>> During my vboxguest Linux cleanup work I made a small
>>> detour to the vboxsf driver.
>>> I noticed that although it depends on vboxguest to make
>>> hgcm calls, it still comes with its own copy of
>>> GenericRequest, Physheap, Init and VMMDev.c
>>> It seems the only reason it uses this is to get
>>> g_vbgldata.hostVersion so that it can check for
>>> page-list support.
>>> IMHO it would be better if the vboxguest driver were
>>> to store the hostVersion in an exported global
>>> variable, say vbg_host_version. And then
>>> vboxfs would use that. Combine that with moving:
>>> struct VBGLHGCMHANDLEDATA aHGCMHandleData[64];
>>>   From g_vbgldata to static globals in HGCM.c
>>> and then g_vbgldata can be dropped from
>>> VBGLInternal.h together with dropping
>>> GenericRequest, Physheap, Init and VMMDev.c
>>> completely.
>>> I've attached a patch which does this from my
>>> own local vboxsf version.
>> Ok, that version was no good, I did not notice that
>> some of the removed code was responsible for
>> calling vbglR0HGCMInit(), here is a new version
>> replacing the VbglR0SfInit call with vbglR0HGCMInit.
> HGCM.cpp
> I have just started reviewing the patch, as the person most familiar
> with the code is away just now.  I am not terribly familiar with the
> code, but I have had to go through it on occasion in the past, and my
> first thought is that this might cause problems on other platforms,
> since the common code is shared by the Windows and Solaris drivers.  I
> will give you an update when I have read more code.


I tried your patch. The first problem was that the first file to be patched is 
HGCM.cpp, not HGCM.c. That was easily fixed.

The second problem is that when I try to load vboxsf.ko in a guest, I get a 
message that vbg_host_version is an unknown symbol.

Thanks for your efforts,


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