Re: [Xen-devel] [PATCH v2 3/3] xen_machine_pv: do not create a dummy CPU in machine->init

[Andreas Färber <afaerber@xxxxxxx>]

Am 29.05.2013 13:34, schrieb Stefano Stabellini:
> This fixes a regression introduced by:
> 
> commit 62fc403f11523169eb4264de31279745f48e3ecc
> Author: Igor Mammedov <imammedo@xxxxxxxxxx>
> Date:   Mon Apr 29 18:54:13 2013 +0200
> 
>     target-i386: Attach ICC bus to CPU on its creation
> 
>     X86CPU should have parent bus so it could provide bus for child APIC.
> 
> The commit makes it mandatory to pass a valid ICC bus to cpu_x86_create,
> but cpu_x86_init just passes NULL to it.

This is not entirely accurate: The ICC bus is only needed for softmmu,
the envisioned remaining use case of cpu_x86_init() was bsd/linux-user.

And sorry for not catching this use case, I was in a hurry for the Hard
Freeze.

> xen_machine_pv uses cpu_x86_init, therefore it has been broken.
> 
> This patch fixes the problem by removing the dummy CPU creation
> altogether from xen_init_pv, relying on the fact that QEMU can now cope
> with a machine without an emulated CPU.
> 
> This fix should be backported to QEMU 1.5.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> CC: imammedo@xxxxxxxxxx
> CC: qemu-stable@xxxxxxxxxx

Change looks okay,

Reviewed-by: Andreas Färber <afaerber@xxxxxxx>

But for the future please avoid "this patch" in the commit message
(because later on it's a "commit", not a patch) and also please put
additional notices such as for backporting below the --- line.

Cheers,
Andreas

> ---
>  hw/i386/xen_machine_pv.c |   16 ----------------
>  1 files changed, 0 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/i386/xen_machine_pv.c b/hw/i386/xen_machine_pv.c
> index f829a52..9f2e291 100644
> --- a/hw/i386/xen_machine_pv.c
> +++ b/hw/i386/xen_machine_pv.c
> @@ -23,7 +23,6 @@
>   */
>  
>  #include "hw/hw.h"
> -#include "hw/i386/pc.h"
>  #include "hw/boards.h"
>  #include "hw/xen/xen_backend.h"
>  #include "xen_domainbuild.h"
> @@ -31,27 +30,12 @@
>  
>  static void xen_init_pv(QEMUMachineInitArgs *args)
>  {
> -    const char *cpu_model = args->cpu_model;
>      const char *kernel_filename = args->kernel_filename;
>      const char *kernel_cmdline = args->kernel_cmdline;
>      const char *initrd_filename = args->initrd_filename;
> -    X86CPU *cpu;
> -    CPUState *cs;
>      DriveInfo *dinfo;
>      int i;
>  
> -    /* Initialize a dummy CPU */
> -    if (cpu_model == NULL) {
> -#ifdef TARGET_X86_64
> -        cpu_model = "qemu64";
> -#else
> -        cpu_model = "qemu32";
> -#endif
> -    }
> -    cpu = cpu_x86_init(cpu_model);
> -    cs = CPU(cpu);
> -    cs->halted = 1;
> -
>      /* Initialize backend core & drivers */
>      if (xen_be_init() != 0) {
>          fprintf(stderr, "%s: xen backend core setup failed\n", __FUNCTION__);
> 


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