Re: [PATCH v3] system: Select HVF by default when no other accelerator is available

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Dec 03, 2024 at 10:42:32AM +0100, Philippe Mathieu-Daudé wrote:
> When testing with a HVF-only binary, we get:
> 
>    3/12 qemu:func-quick+func-aarch64 / func-aarch64-version                                      ERROR            0.29s   exit status 1
>   stderr:
>   Traceback (most recent call last):
>     File "tests/functional/test_version.py", line 22, in test_qmp_human_info_version
>       self.vm.launch()
>     File "machine/machine.py", line 461, in launch
>       raise VMLaunchFailure(
>   qemu.machine.machine.VMLaunchFailure: ConnectError: Failed to establish session: EOFError
>       Exit code: 1
>       Command: build/qemu-system-aarch64 -display none -vga none -chardev socket,id=mon,fd=5 -mon chardev=mon,mode=control -machine none -nodefaults
>       Output: qemu-system-aarch64: No accelerator selected and no default accelerator available
> 
> Fix by checking for HVF in configure_accelerators() and using
> it by default when no other accelerator is available.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> v2 was https://lore.kernel.org/qemu-devel/20241203091036.59898-1-philmd@linaro.org/
> ---
>  system/vl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/system/vl.c b/system/vl.c
> index 54998fdbc7e..2f855d83fbb 100644
> --- a/system/vl.c
> +++ b/system/vl.c
> @@ -2362,6 +2362,7 @@ static void configure_accelerators(const char *progname)
>              /* Select the default accelerator */
>              bool have_tcg = accel_find("tcg");
>              bool have_kvm = accel_find("kvm");
> +            bool have_hvf = accel_find("hvf");
>  
>              if (have_tcg && have_kvm) {
>                  if (g_str_has_suffix(progname, "kvm")) {
> @@ -2374,6 +2375,8 @@ static void configure_accelerators(const char *progname)
>                  accelerators = "kvm";
>              } else if (have_tcg) {
>                  accelerators = "tcg";
> +            } else if (have_hvf) {
> +                accelerators = "hvf";
>              } else {
>                  error_report("No accelerator selected and"
>                               " no default accelerator available");


Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


This is a no-brainer first step IMHO, given it passes all functional tests.

I think we should subsequently consider whether to even rank HVF above
TCG, on the basis that HW acceleration is faster and should provide a
host<->guest security boundary that we don't claim for TCG


With regards,
Daniel
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