Re: [PATCH v2 3/3] configure: add libdaxctl support

[Liu, Jingqi]

On 4/29/2020 12:23 AM, Joao Martins wrote:

> On 4/15/20 4:35 AM, Jingqi Liu wrote:
> > Add a pair of configure options --{enable,disable}-libdaxctl to control
> > whether QEMU is compiled with libdaxctl [1]. Libdaxctl is a utility
> > library for managing the device dax subsystem.
> >
> > QEMU uses mmap(2) to maps vNVDIMM backends and aligns the mapping
> > address to the page size (getpagesize(2)) by default. However, some
> > types of backends may require an alignment different than the page
> > size. The 'align' option is provided to memory-backend-file to allow
> > users to specify the proper alignment.
> >
> > For device dax (e.g., /dev/dax0.0), the 'align' option needs to match
> > the alignment requirement of the device dax, which can be fetched
> > through the libdaxctl APIs.
> >
> > [1] Libdaxctl is a part of ndctl project.
> > The project's repository is: https://github.com/pmem/ndctl
> >
> > For more information about libdaxctl APIs, you can refer to the
> > comments in source code of: pmem/ndctl/daxctl/lib/libdaxctl.c.
> >
> > Signed-off-by: Jingqi Liu <address@hidden>
> > ---
> >  configure | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/configure b/configure
> > index e225a1e3ff..df1752cf08 100755
> > --- a/configure
> > +++ b/configure
> > @@ -509,6 +509,7 @@ libpmem=""
> >  default_devices="yes"
> >  plugins="no"
> >  fuzzing="no"
> > +libdaxctl=""
> >  
> >  supported_cpu="no"
> >  supported_os="no"
> > @@ -1601,6 +1602,10 @@ for opt do
> >    ;;
> >    --gdb=*) gdb_bin="$optarg"
> >    ;;
> > +  --enable-libdaxctl) libdaxctl=yes
> > +  ;;
> > +  --disable-libdaxctl) libdaxctl=no
> > +  ;;
> >    *)
> >        echo "ERROR: unknown option $opt"
> >        echo "Try '$0 --help' for more information"
> > @@ -1894,6 +1899,7 @@ disabled with --disable-FEATURE, default is enabled if available:
> >    debug-mutex     mutex debugging support
> >    libpmem         libpmem support
> >    xkbcommon       xkbcommon support
> > +  libdaxctl       libdaxctl support
> >  
> >  NOTE: The object files are built at the place where configure is launched
> >  EOF
> > @@ -6190,6 +6196,25 @@ if test "$libpmem" != "no"; then
> >  	fi
> >  fi
> >  
> > +##########################################
> > +# check for libdaxctl
> > +
> > +if test "$libdaxctl" != "no"; then
> > +	if $pkg_config --exists "libdaxctl"; then
> > +		libdaxctl="yes"
> > +		libdaxctl_libs=$($pkg_config --libs libdaxctl)
> > +		libdaxctl_cflags=$($pkg_config --cflags libdaxctl)
> > +		libs_softmmu="$libs_softmmu $libdaxctl_libs"
> > +		QEMU_CFLAGS="$QEMU_CFLAGS $libdaxctl_cflags"
> > +	else
> > +		if test "$libdaxctl" = "yes" ; then
> > +			feature_not_found "libdaxctl" "Install libdaxctl"
> > +		fi
> >       
> Region iteration APIs, align and path getter routines are only available since
> libdaxctl v56/v57 (the latest is v68).
>
> Not sure how likely this happens in today's distros but if we care about systems
> with < v57 we should probably check that
> daxctl_region_foreach/daxctl_region_get_align/daxctl_region_get_path symbols
> exist? Or alternatively requiring v57 or up which serves as a bandage, but more
> long term ... any usage of newer daxctl APIs will require the former.
>     
Thanks for your suggestion.
Better to require v57 or up. 
How about adding the following check:
+       if $pkg_config --atleast-version=57 "libdaxctl"; then


Jingqi