[libvirt PATCH 4/5] qemu: probe for "-cpu max" support

[Pavel Hrdina]

On Tue, Feb 09, 2021 at 01:59:00PM +0000, Daniel P. Berrangé wrote:
> This is a special CPU model similar to "-cpu host", so won't use our
> normal CPU model detection logic.
> 
> Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> ---
>  src/qemu/qemu_capabilities.c | 11 +++++++++++
>  src/qemu/qemu_capabilities.h |  1 +
>  2 files changed, 12 insertions(+)
> 
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index d0378f94bc..ecfb313d0a 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -614,6 +614,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
>  
>                /* 390 */
>                "vhost-user-blk",
> +              "cpu-max",
>      );
>  
>  
> @@ -2984,12 +2985,22 @@ virQEMUCapsProbeQMPCPUDefinitions(virQEMUCapsPtr qemuCaps,
>                                    virQEMUCapsAccelPtr accel,
>                                    qemuMonitorPtr mon)
>  {
> +    qemuMonitorCPUDefsPtr defs = accel->cpuModels;

accel->cpuModels is NULL here ... [0]

> +    size_t i;
> +
>      if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_DEFINITIONS))
>          return 0;
>  
>      if (virQEMUCapsFetchCPUDefinitions(mon, qemuCaps->arch, &accel->cpuModels) < 0)
>          return -1;
>  
> +    for (i = 0; i < defs->ncpus; i++) {

[0] ... so here it will crash.

> +        if (STREQ_NULLABLE(defs->cpus[i].name, "max")) {
> +            virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_MAX);
> +            break;
> +        }
> +    }
> +

Do we trust QEMU that if accel=kvm supports cpu-max that accel=tcg
supports it as well and is that true on all architectures?

Pavel
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