On Tue, Dec 01, 2015 at 04:04:08PM -0800, Greg Kroah-Hartman wrote:
> On Tue, Dec 01, 2015 at 02:54:20PM -0800, Sinclair Yeh wrote:
> > Hi,
> >
> > On Tue, Dec 01, 2015 at 02:45:27PM -0800, Dmitry Torokhov wrote:
> > > On Tue, Dec 1, 2015 at 2:32 PM, Sinclair Yeh <syeh@xxxxxxxxxx> wrote:
> > > > Hi,
> > > >
> >
> > <snip>
> >
> > > >> > */
> > > >> > -#define VMMOUSE_CMD(cmd, in1, out1, out2, out3, out4) \
> > > >> > -({ \
> > > >> > - unsigned long __dummy1, __dummy2; \
> > > >> > - __asm__ __volatile__ ("inl %%dx" : \
> > > >> > - "=a"(out1), \
> > > >> > - "=b"(out2), \
> > > >> > - "=c"(out3), \
> > > >> > - "=d"(out4), \
> > > >> > - "=S"(__dummy1), \
> > > >> > - "=D"(__dummy2) : \
> > > >> > - "a"(VMMOUSE_PROTO_MAGIC), \
> > > >> > - "b"(in1), \
> > > >> > - "c"(VMMOUSE_PROTO_CMD_##cmd), \
> > > >> > - "d"(VMMOUSE_PROTO_PORT) : \
> > > >> > - "memory"); \
> > > >> > +#define VMMOUSE_CMD(cmd, in1, out1, out2, out3, out4) \
> > > >> > +({ \
> > > >> > + unsigned long __dummy1 = 0, __dummy2 = 0; \
> > > >>
> > > >> Why do we need to initialize dummies?
> > > >
> > > > Because for some commands those parameters to VMW_PORT() can be both
> > > > input and outout.
> > >
> > > The vmmouse commands do not use them as input though, so it seems we
> > > are simply wasting CPU cycles setting them to 0 just because we are
> > > using the new VMW_PORT here. Why do we need to switch? What is the
> > > benefit of doing this?
> >
> > There are two reasons. One is to make the code more readable and
> > maintainable. Rather than having mostly similar inline assembly
> > code sprinkled across multiple modules, we can just use the macros
> > and document that.
>
> But the macro is only used here, and the variables aren't used at all,
> so it makes no sense in this file.
Maybe it's because I didn't CC you on the rest of the series. I wasn't
sure what the proper distribution list is for each part.
This new macro is also used in arch/x86/kernel/cpu/vmware.c and
vmw_balloon.c
>
> > The second reason is this organization makes some on-going future
> > development easier.
>
> We don't plan for "future" development other than a single patch series,
> as we have no idea what that development is, nor if it will really
> happen. You can always change this file later if you need to, nothing
> is keeping that from happening.
So the intent of this series is to centralize similar lines of inline
assembly code that are currently used by 3 different kernel modules
to a central place. The new vmware.h [patch 0/6] becomes the one header
to include for common guest-host communication needs.
> thanks,
>
> greg k-h
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
