Re: [Qemu-devel] [PATCH] accel: Allow to build QEMU without TCG or KVM support

[Anthony PERARD <anthony.perard@citrix.com>]

On Thu, Jan 17, 2019 at 12:06:09PM +0100, Thomas Huth wrote:
> On 2019-01-17 11:55, Anthony PERARD wrote:
> > On Thu, Jan 17, 2019 at 07:02:24AM +0100, Thomas Huth wrote:
> >> On 2019-01-16 18:35, Anthony PERARD wrote:
> >>> Instead of deny build of QEMU without a default accelerator, simply
> >>> report an error when the user haven't passed -accel or -machine accel=
> >>> and TCG and KVM isn't builtin.
> >>>
> >>> ./configure already check that at least one accelerator is available.
> >>>
> >>> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> >>> ---
> >>>  accel/accel.c | 4 +++-
> >>>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/accel/accel.c b/accel/accel.c
> >>> index 68b6d56323..0d5b370dfd 100644
> >>> --- a/accel/accel.c
> >>> +++ b/accel/accel.c
> >>> @@ -91,7 +91,9 @@ void configure_accelerator(MachineState *ms, const char *progname)
> >>>  #elif defined(CONFIG_KVM)
> >>>              accel = "kvm";
> >>>  #else
> >>> -#error "No default accelerator available"
> >>> +            error_report("No accelerator selected and"
> >>> +                         " no default accelerator available");
> >>> +            exit(1);
> >>>  #endif
> >>>          }
> >>>      }
> >>
> >> That looks a little bit friendlier, indeed.
> >>
> >> Reviewed-by: Thomas Huth <thuth@redhat.com>
> >>
> >> Out of curiosity: Did you hit the #error while compiling? Or just by
> >> reading the recent patches?
> > 
> > I've hit the #error. I often build QEMU with --disable-tcg --disable-kvm
> > --enable-xen just because I only need to build/test xen. So if I can
> > disable features that I don't need to build QEMU a tiny bit faster, I do
> > :).
> 
> Oh, good to know that this configuration works, too. Maybe you should
> also add a
> 
> #elif defined(CONFIG_XEN)
> 	accel = "xen";
> #...
> 
> part in that case?

I though about it, but I don't think that's a good idea. We can't start
a Xen guests with QEMU alone, so there is always some toolstack that is
going to generate the command line anyway. So it's better to always
require "-machine accel=xen".

Thanks,

-- 
Anthony PERARD