Re: [Qemu-devel] [PATCH v5 22/45] postcopy: OS support test

[Dr. David Alan Gilbert]

* Paolo Bonzini (address@hidden) wrote:
> 
> 
> On 30/03/2015 16:07, Dr. David Alan Gilbert wrote:
> >>> > > 
> >> > 
> >> > You would just require new _installed_ kernel headers.  Then you can use
> >> > linux/userfaultfd.h and syscall.h (the latter from glibc, includes
> >> > asm/unistd.h to get syscall numbers).
> >> > 
> >> > linux-headers/ is useful for APIs that do not require system calls, or
> >> > for APIs that are extensible.  However, if a system call is required
> >> > (and mandatory) it's simpler to just use installed headers.
> > OK, so then I could check for ifdef __NR_userfault and then
> > do the include and I think that would be safe.
> 
> I think it's okay.  First include syscall.h, then include
> linux/userfaultfd.h under #ifdef.
> 
> > Although then what's the best way to tell people to try it out
> > without an updated libc?
> 
> They don't need an updated libc, just an updated kernel.  syscall.h is
> just a wrapper around Linux headers.

That's what I've implemented in the v6 and the v7 I've just posted.

Dave

> 
> Paolo
> 
> > Or is it best to modify ./configure to detect it?
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK