Re: [PATCH v3] kvm: replace fprintf with error_report/printf() in kvm_init()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 12/8/24 11:59, Ani Sinha wrote:
> 
> 
> On Mon, 12 Aug, 2024, 3:23 pm Ani Sinha, <anisinha@redhat.com 
> <mailto:anisinha@redhat.com>> wrote:
> 
>     On Fri, Aug 9, 2024 at 2:06 PM Philippe Mathieu-Daudé
>     <philmd@linaro.org <mailto:philmd@linaro.org>> wrote:
>      >
>      > Hi Ani,
>      >
>      > On 9/8/24 08:49, Ani Sinha wrote:
>      > > error_report() is more appropriate for error situations.
>     Replace fprintf with
>      > > error_report. Cosmetic. No functional change.
>      > >
>      > > CC: qemu-trivial@nongnu.org <mailto:qemu-trivial@nongnu.org>
>      > > CC: zhao1.liu@intel.com <mailto:zhao1.liu@intel.com>
>      >
>      > (Pointless to carry Cc line when patch is already reviewed next line)
>      >
>      > > Reviewed-by: Zhao Liu <zhao1.liu@intel.com
>     <mailto:zhao1.liu@intel.com>>
>      > > Signed-off-by: Ani Sinha <anisinha@redhat.com
>     <mailto:anisinha@redhat.com>>
>      > > ---
>      > >   accel/kvm/kvm-all.c | 40 ++++++++++++++++++----------------------
>      > >   1 file changed, 18 insertions(+), 22 deletions(-)
>      > >
>      > > changelog:
>      > > v2: fix a bug.
>      > > v3: replace one instance of error_report() with error_printf().
>     added tags.
>      > >
>      > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
>      > > index 75d11a07b2..5bc9d35b61 100644
>      > > --- a/accel/kvm/kvm-all.c
>      > > +++ b/accel/kvm/kvm-all.c
>      > > @@ -2427,7 +2427,7 @@ static int kvm_init(MachineState *ms)
>      > >       QLIST_INIT(&s->kvm_parked_vcpus);
>      > >       s->fd = qemu_open_old(s->device ?: "/dev/kvm", O_RDWR);
>      > >       if (s->fd == -1) {
>      > > -        fprintf(stderr, "Could not access KVM kernel module:
>     %m\n");
>      > > +        error_report("Could not access KVM kernel module: %m");
>      > >           ret = -errno;
>      > >           goto err;
>      > >       }
>      > > @@ -2437,13 +2437,13 @@ static int kvm_init(MachineState *ms)
>      > >           if (ret >= 0) {
>      > >               ret = -EINVAL;
>      > >           }
>      > > -        fprintf(stderr, "kvm version too old\n");
>      > > +        error_report("kvm version too old");
>      > >           goto err;
>      > >       }
>      > >
>      > >       if (ret > KVM_API_VERSION) {
>      > >           ret = -EINVAL;
>      > > -        fprintf(stderr, "kvm version not supported\n");
>      > > +        error_report("kvm version not supported");
>      > >           goto err;
>      > >       }
>      > >
>      > > @@ -2488,26 +2488,22 @@ static int kvm_init(MachineState *ms)
>      > >       } while (ret == -EINTR);
>      > >
>      > >       if (ret < 0) {
>      > > -        fprintf(stderr, "ioctl(KVM_CREATE_VM) failed: %d
>     %s\n", -ret,
>      > > -                strerror(-ret));
>      > > +        error_report("ioctl(KVM_CREATE_VM) failed: %d %s", -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");
>      > > +            error_report("Host kernel setup problem detected.
>      >
>      > \n"
>      >
>      > Should we use error_printf_unless_qmp() for the following?
> 
>     Do you believe that qemu_init() -> configure_accelerators() ->
>     do_configure_accelerator,() -> accel_init_machine() -> kvm_init()  can
>     be called from QMP context?
> 
> 
> To clarify, that is the only path I saw that calls kvm_init()

We don't know whether this code can end refactored or not.
Personally I rather consistent API uses, since snipped of
code are often used as example. Up to the maintainer.

>      >
>      > " Please verify:");
>      > > +            error_report("- for kernels supporting the
>     switch_amode or"
>      > > +                        " user_mode parameters, whether");
>      > > +            error_report("  user space is running in primary
>     address space");
>      > > +            error_report("- for kernels supporting the
>     vm.allocate_pgste "
>      > > +                        "sysctl, whether it is enabled");
>      > >           }
>      > >   #elif defined(TARGET_PPC)
>      > >           if (ret == -EINVAL) {
>      > > -            fprintf(stderr,
>      > > -                    "PPC KVM module is not loaded.
>      >
>      > \n"
>      >
>      > Ditto.
>      >
>      > " Try modprobe kvm_%s.\n",
>      > > -                    (type == 2) ? "pr" : "hv");
>      > > +            error_report("PPC KVM module is not loaded. Try
>     modprobe kvm_%s.",
>      > > +                        (type == 2) ? "pr" : "hv");
>      > >           }
>      > >   #endif
>      > >           goto err;
>      > > @@ -2526,9 +2522,9 @@ static int kvm_init(MachineState *ms)
>      > >                           nc->name, nc->num, soft_vcpus_limit);
>      > >
>      > >               if (nc->num > hard_vcpus_limit) {
>      > > -                fprintf(stderr, "Number of %s cpus requested
>     (%d) exceeds "
>      > > -                        "the maximum cpus supported by KVM
>     (%d)\n",
>      > > -                        nc->name, nc->num, hard_vcpus_limit);
>      > > +                error_report("Number of %s cpus requested (%d)
>     exceeds "
>      > > +                             "the maximum cpus supported by
>     KVM (%d)",
>      > > +                             nc->name, nc->num, hard_vcpus_limit);
>      > >                   exit(1);
>      > >               }
>      > >           }
>      > > @@ -2542,8 +2538,8 @@ static int kvm_init(MachineState *ms)
>      > >       }
>      > >       if (missing_cap) {
>      > >           ret = -EINVAL;
>      > > -        fprintf(stderr, "kvm does not support %s\n%s",
>      > > -                missing_cap->name, upgrade_note);
>      > > +        error_printf("kvm does not support %s\n%s",
>      > > +                     missing_cap->name, upgrade_note);
>      >
>      > Similarly, should we print upgrade_note using
>     error_printf_unless_qmp?
>      >
>      > >           goto err;
>      > >       }
>      > >
>      >
>