Re: [PATCH v2] kvm: refactor core virtual machine creation into its own function

[Zhao Liu <zhao1.liu@intel.com>]

Hi Ani,

On Thu, Aug 08, 2024 at 05:08:38PM +0530, Ani Sinha wrote:
> Date: Thu,  8 Aug 2024 17:08:38 +0530
> From: Ani Sinha <anisinha@redhat.com>
> Subject: [PATCH v2] kvm: refactor core virtual machine creation into its
>  own function
> X-Mailer: git-send-email 2.45.2
> 
> Refactoring the core logic around KVM_CREATE_VM into its own separate function
> so that it can be called from other functions in subsequent patches. There is
> no functional change in this patch.
> 
> CC: pbonzini@redhat.com
> CC: zhao1.liu@intel.com
> Signed-off-by: Ani Sinha <anisinha@redhat.com>
> ---
>  accel/kvm/kvm-all.c | 93 +++++++++++++++++++++++++++------------------
>  1 file changed, 56 insertions(+), 37 deletions(-)
> 
> changelog:
> v2: s/fprintf/warn_report as suggested by zhao

Thanks for your change!

> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 75d11a07b2..c2e177c39f 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2385,6 +2385,60 @@ uint32_t kvm_dirty_ring_size(void)
>      return kvm_state->kvm_dirty_ring_size;
>  }
>  
> +static int do_kvm_create_vm(MachineState *ms, int type)
> +{
> +    KVMState *s;
> +    int ret;
> +
> +    s = KVM_STATE(ms->accelerator);
> +
> +    do {
> +        ret = kvm_ioctl(s, KVM_CREATE_VM, type);
> +    } while (ret == -EINTR);
> +
> +    if (ret < 0) {
> +        warn_report("ioctl(KVM_CREATE_VM) failed: %d %s", -ret,
> +                    strerror(-ret));
> +
> +#ifdef TARGET_S390X
> +        if (ret == -EINVAL) {
> +            warn_report("Host kernel setup problem detected. Please verify:");
> +            warn_report("- for kernels supporting the switch_amode or"
> +                        " user_mode parameters, whether");
> +            warn_report("  user space is running in primary address space");
> +            warn_report("- for kernels supporting the vm.allocate_pgste "
> +                        "sysctl, whether it is enabled");
> +        }
> +#elif defined(TARGET_PPC)
> +        if (ret == -EINVAL) {
> +            warn_report("PPC KVM module is not loaded. Try modprobe kvm_%s.",
> +                        (type == 2) ? "pr" : "hv");
> +        }
> +#endif

I think error level message is more appropriate than warn because after
the print QEMU handles error and terminates the Guest startup.

What about the following change?

#ifdef TARGET_S390X
        if (ret == -EINVAL) {
            error_report("Host kernel setup problem detected");
            error_printf("Please verify:\n");
            error_printf("- for kernels supporting the switch_amode or"
                         " user_mode parameters, whether\n");
            error_printf("  user space is running in primary address space\n");
            error_printf("- for kernels supporting the vm.allocate_pgste "
                         "sysctl, whether it is enabled\n");
        }
#elif defined(TARGET_PPC)
        if (ret == -EINVAL) {
            error_report("PPC KVM module is not loaded");
            error_printf("Try modprobe kvm_%s.\n",
                         (type == 2) ? "pr" : "hv");
	}
#endif

The above uses error_report() to just print error reason/error code
since for error_report, "The resulting message should be a single
phrase, with no newline or trailing punctuation."

Other specific hints or information are printed by error_printf()
because style.rst suggests "Use error_printf() & friends to print
additional information."

Thanks,
Zhao

> +    }
> +
> +    return ret;
> +}
> +
> +static int find_kvm_machine_type(MachineState *ms)
> +{
> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
> +    int type;
> +
> +    if (object_property_find(OBJECT(current_machine), "kvm-type")) {
> +        g_autofree char *kvm_type;
> +        kvm_type = object_property_get_str(OBJECT(current_machine),
> +                                           "kvm-type",
> +                                           &error_abort);
> +        type = mc->kvm_type(ms, kvm_type);
> +    } else if (mc->kvm_type) {
> +        type = mc->kvm_type(ms, NULL);
> +    } else {
> +        type = kvm_arch_get_default_type(ms);
> +    }
> +    return type;
> +}
> +
>  static int kvm_init(MachineState *ms)
>  {
>      MachineClass *mc = MACHINE_GET_CLASS(ms);
> @@ -2467,49 +2521,14 @@ static int kvm_init(MachineState *ms)
>      }
>      s->as = g_new0(struct KVMAs, s->nr_as);
>  
> -    if (object_property_find(OBJECT(current_machine), "kvm-type")) {
> -        g_autofree char *kvm_type = object_property_get_str(OBJECT(current_machine),
> -                                                            "kvm-type",
> -                                                            &error_abort);
> -        type = mc->kvm_type(ms, kvm_type);
> -    } else if (mc->kvm_type) {
> -        type = mc->kvm_type(ms, NULL);
> -    } else {
> -        type = kvm_arch_get_default_type(ms);
> -    }
> -
> +    type = find_kvm_machine_type(ms);
>      if (type < 0) {
>          ret = -EINVAL;
>          goto err;
>      }
>  
> -    do {
> -        ret = kvm_ioctl(s, KVM_CREATE_VM, type);
> -    } while (ret == -EINTR);
> -
> +    ret = do_kvm_create_vm(ms, type);
>      if (ret < 0) {
> -        fprintf(stderr, "ioctl(KVM_CREATE_VM) failed: %d %s\n", -ret,
> -                strerror(-ret));
> -
> -#ifdef TARGET_S390X
> -        if (ret == -EINVAL) {
> -            fprintf(stderr,
> -                    "Host kernel setup problem detected. Please verify:\n");
> -            fprintf(stderr, "- for kernels supporting the switch_amode or"
> -                    " user_mode parameters, whether\n");
> -            fprintf(stderr,
> -                    "  user space is running in primary address space\n");
> -            fprintf(stderr,
> -                    "- for kernels supporting the vm.allocate_pgste sysctl, "
> -                    "whether it is enabled\n");
> -        }
> -#elif defined(TARGET_PPC)
> -        if (ret == -EINVAL) {
> -            fprintf(stderr,
> -                    "PPC KVM module is not loaded. Try modprobe kvm_%s.\n",
> -                    (type == 2) ? "pr" : "hv");
> -        }
> -#endif
>          goto err;
>      }
>  
> -- 
> 2.45.2
>