On Wed, 6 Sep 2017 11:49:27 +0200
Cornelia Huck <coh...@redhat.com> wrote:
> configure_accelerator() falls back to tcg if no accelerator has
> been specified. Formerly, we could be sure that tcg is always
> available; however, with --disable-tcg, this is not longer true,
> and you are not able to start qemu without explicitly specifying
> another accelerator on those builds.
>
> Instead, choose an accelerator in the order tcg->kvm->xen->hax.
>
> Signed-off-by: Cornelia Huck <coh...@redhat.com>
> ---
>
> RFC mainly because this breaks iotest 186 in a different way on a
> tcg-less x86_64 build: Before, it fails with "-machine accel=tcg: No
> accelerator found"; afterwards, there seems to be a difference in
> output due to different autogenerated devices. Not sure how to handle
> that.
>
> cc:ing some hopefully interested folks (-ENOMAINTAINER again).
>
> ---
> accel/accel.c | 22 ++++++++++++++++++++--
> arch_init.c | 17 +++++++++++++++++
> include/sysemu/arch_init.h | 2 ++
> qemu-options.hx | 6 ++++--
> 4 files changed, 43 insertions(+), 4 deletions(-)
>
> diff --git a/accel/accel.c b/accel/accel.c
> index 8ae40e1e13..26a3f32627 100644
> --- a/accel/accel.c
> +++ b/accel/accel.c
> @@ -68,6 +68,25 @@ static int accel_init_machine(AccelClass *acc,
> MachineState *ms)
> return ret;
> }
>
> +static const char *default_accelerator(void)
> +{
> + if (tcg_available()) {
> + return "tcg";
> + }
> + if (kvm_available()) {
> + return "kvm";
> + }
> + if (xen_available()) {
> + return "xen";
> + }
> + if (hax_available()) {
> + return "hax";
> + }
> + /* configure makes sure we have at least one accelerator */
> + g_assert(false);
> + return "";
> +}
> +
> void configure_accelerator(MachineState *ms)
> {
> const char *accel, *p;
> @@ -79,8 +98,7 @@ void configure_accelerator(MachineState *ms)
>
> accel = qemu_opt_get(qemu_get_machine_opts(), "accel");
> if (accel == NULL) {
> - /* Use the default "accelerator", tcg */
> - accel = "tcg";
> + accel = default_accelerator();
It actually may be easier to just switch the default to
"tcg:kvm:xen:hax". Haven't tested that, though.
> }
>
> p = accel;
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9f6e2adfff..386e6e945d 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -66,7 +66,8 @@ Supported machine properties are:
> @table @option
> @item accel=@var{accels1}[:@var{accels2}[:...]]
> This is used to enable an accelerator. Depending on the target architecture,
> -kvm, xen, hax or tcg can be available. By default, tcg is used. If there is
> +kvm, xen, hax or tcg can be available. By default, the first one available
> +out of tcg, kvm, xen, hax (in that order) is used. If there is
> more than one accelerator specified, the next one is used if the previous one
> fails to initialize.
> @item kernel_irqchip=on|off
> @@ -126,7 +127,8 @@ STEXI
> @item -accel @var{name}[,prop=@var{value}[,...]]
> @findex -accel
> This is used to enable an accelerator. Depending on the target architecture,
> -kvm, xen, hax or tcg can be available. By default, tcg is used. If there is
> +kvm, xen, hax or tcg can be available. By default, the first one available
> +out of tcg, kvm, xen, hax (in that order) is used. If there is
> more than one accelerator specified, the next one is used if the previous one
> fails to initialize.
> @table @option
These changes would still apply, as would the question about what to do
with the iotest.
