Re: [patch] Re: [Qemu-devel] Suggestion - trap window-close of VM

[Asko Kauppi <asko.kauppi@sci.fi>]

Would it be too hard to implement a proper "state save" such as in 
Virtual PC and others?  In my experience, that single feature is the 
most important of any emulation system; ability to work for a while, 
then suspend the whole system for days, weeks, or years, and catching 
up where you last left it.

Is there some practical reason why QEmu should not offer this?

-ak


28.3.2005 kello 14:34, Struan Bartlett kirjoitti:

   Hi,
>
>  I've attached a patch against the 2005-03-26 snapshot that implements 
> two '-on-quit' options for the emulator window: ignore-unless-halted 
> and suspend-unless-halted, that aim to make it safe to allow naive 
> users to (try to) close the VM window by trapping requests to shutdown 
> and either ignoring them or forcing a save of the VM state before 
> obeying them.
>
>  Caveat: I'll come clean straight away that the patch is implemented 
> using a nasty TARGET_i386-specific hack that detects whether the guest 
> operating system has permanently halted by looking to see if the last 
> instruction executed was 0xF4 and, if so, whether the IF flag is 
> cleared. Saying that, this system appears to work reasonably well on 
> my Pentium host running a Windows 2000 guest, but I have not tested it 
> on any other systems.
>
>  Usage:
>
>  1. If you provide naive users with a variation on the following 
> command line, then you can let your naive users (try to) close the VM 
> window as much as they like. Unless the guest has permanently halted, 
> attempts to close the VM window should save the VM state to 
> 'suspended.qemu' in the current working directory before qemu exits. 
> The same command line will restart the VM where it left off. Then, 
> once the guest has permanently halted, qemu will delete the 
> suspended.qemu file so that the next launch of qemu will boot afresh:
>
> qemu -hda win2k.raw -m 64 -monitor null -loadvm suspended.qemu 
> -on-quit suspend-unless-halted
>
>  2. Alternatively, the following command will make qemu ignore the 
> user's request to close the emulator window unless the guest has 
> already permanently halted:
>
> qemu -hda win2k.raw -m 64 -monitor null -on-quit ignore-unless-halted
>
>  3. If you combine this with a test of whether qemu is already 
> running, then it should be safe to let naive users try to both launch 
> and to close qemu as much as they like. e.g.
>
> killall -0 qemu 2>/dev/null; if [ $? == 1 ]; then qemu -hda win2k.raw 
> -m 64 -monitor null -loadvm suspended.qemu -on-quit 
> suspend-unless-halted; fi &
>
>  4. Finally, if your leave out the -on-quit option altogether, then 
> qemu's behaviour should remain completely unchanged.
>
>  I hope this is useful for some i386/W2K users out there. Any 
> constructive criticism appreciated. If you know how I could improve 
> permanent halt detection (that doesn't require in-depth knowledge of 
> APM or ACPI) then please let me know.
>
>  Struan
>
>  Struan Bartlett wrote:
>  Ryan Rempel wrote:
> On Mon, Nov 29, 2004 at 21:46:54 +0100, Lennert Buytenhek wrote
>
> On Mon, Nov 29, 2004 at 08:43:56PM +0000, Richard Neill wrote:
>
> A thought that occurred to me. If one is running a virtual machine (eg
> copy of WinXP), then simply closing the qemu window is a really bad
> idea, since it will effectively crash the guest.
>
> Related thought -- it would be way cool if we could make killing qemu
> do exactly happens when you press the power button on an ACPI-capable
> machine with any recent OS on it (auto shutdown.)
>
> I was wondering if anyone has followed up on this suggestion. I'm
> putting together a Qemu-based setup for some relatively naive users,
> and ideally I'd like to be able to deal with this in a reasonable
> elegant way (the ACPI hook sounds very elegant indeed).
>
> Alternatively, how do people deal with the problem of naive users who
> might just close the Qemu window without shutting down the guest
> properly? I'm working in a KDE environment -- perhaps there is a way
> in KDE to prevent the close button from appearing? But that wouldn't
> catch every case either (for instance, if the user were to shut down
> the host).
>  This sounds like a good idea. An alternative solution, that might be 
> more straightforward to implement if Qemu doesn't implement ACPI yet, 
> would be for the kill signal to simply cause Qemu to do the equivalent 
> of entering 'stop' and 'savevm <somefilepath>' into the monitor.
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>
> --- qemu-snapshot-2005-03-26_23/vl.c	Sun Mar 13 17:59:37 2005
> +++ qemu-snapshot-2005-03-26_23-on-quit/vl.c	Mon Mar 28 02:06:52 2005
> @@ -139,6 +139,9 @@
>  int graphic_height = 600;
>  int graphic_depth = 15;
>  int full_screen = 0;
> +#ifdef TARGET_I386
> +int on_quit = 0;
> +#endif
>  TextConsole *vga_console;
>  CharDriverState *serial_hds[MAX_SERIAL_PORTS];
>  CharDriverState *parallel_hds[MAX_PARALLEL_PORTS];
> @@ -2675,6 +2678,17 @@
>                          qemu_get_clock(rt_clock));
>  }
>
> +#ifdef TARGET_I386
> +int ishalted() {
> +   uint8_t buf[16];
> +   uint64_t v;
> +	
> +   cpu_memory_rw_debug(cpu_single_env, cpu_single_env->eip-1, buf, 
> 16, 0);
> +   v = ldub_raw(buf);
> +   return (v == 0xf4) && ( !(cpu_single_env->eflags & 0x200) );
> +}
> +#endif
> +
>  int main_loop(void)
>  {
>      int ret, timeout;
> @@ -2684,9 +2698,16 @@
>          if (vm_running) {
>              ret = cpu_exec(env);
>              if (shutdown_requested) {
> +#ifdef TARGET_I386	
> +	       if( on_quit == 0 || on_quit == 2 || ( on_quit == 1 && 
> ishalted() ) ) {
> +#endif		
>                  ret = EXCP_INTERRUPT;
>                  break;
>              }
> +#ifdef TARGET_I386	
> + 	       shutdown_requested = 0;
> + 	    }
> +#endif
>              if (reset_requested) {
>                  reset_requested = 0;
>                  qemu_system_reset();
> @@ -2783,6 +2804,11 @@
>             "-std-vga        simulate a standard VGA card with VESA 
> Bochs Extensions\n"
>             "                (default is CL-GD5446 PCI VGA)\n"
>  #endif
> +#ifdef TARGET_I386
> +	   "-on-quit [ignore-unless-halted|suspend-unless-halted]\n"
> +	   "                select the behaviour when the emulator window is 
> asked to quit\n"
> +	   "                (default is none)\n"
> +#endif
>             "-loadvm file    start right away with a saved state 
> (loadvm in monitor)\n"
>             "\n"
>             "During emulation, the following keys are useful:\n"
> @@ -2864,6 +2890,10 @@
>      QEMU_OPTION_full_screen,
>      QEMU_OPTION_pidfile,
>      QEMU_OPTION_no_kqemu,
> +
> +#ifdef TARGET_I386	
> +    QEMU_OPTION_on_quit
> +#endif
>  };
>
>  typedef struct QEMUOption {
> @@ -2932,6 +2962,9 @@
>      { "loadvm", HAS_ARG, QEMU_OPTION_loadvm },
>      { "full-screen", 0, QEMU_OPTION_full_screen },
>      { "pidfile", HAS_ARG, QEMU_OPTION_pidfile },
> +#ifdef TARGET_I386
> +    { "on-quit", HAS_ARG, QEMU_OPTION_on_quit },
> +#endif
>
>      /* temporary options */
>      { "pci", 0, QEMU_OPTION_pci },
> @@ -3383,6 +3416,19 @@
>              case QEMU_OPTION_pidfile:
>                  create_pidfile(optarg);
>                  break;
> +#ifdef TARGET_I386   	
> +            case QEMU_OPTION_on_quit:
> +	        if(!strcmp(optarg, "ignore-unless-halted")) {
> +		   fprintf(stderr, "%s enabled\n", optarg);
> +		   on_quit = 1;
> +		}
> +		else if(!strcmp(optarg, "suspend-unless-halted")) {
> +		   fprintf(stderr, "%s enabled\n", optarg);
> +		   on_quit = 2;
> +		}
> +	        else on_quit = 0;
> +	        break;
> +#endif	
>  #ifdef USE_KQEMU
>              case QEMU_OPTION_no_kqemu:
>                  kqemu_allowed = 0;
> @@ -3696,6 +3742,23 @@
>          }
>      }
>      main_loop();
> +
> +#ifdef TARGET_I386
> +    if( on_quit == 2 ) {
> +       char *f = "suspended.qemu";
> +       if( ishalted() ) {
> + 	
> + 	 fprintf(stderr, "VM is halted: removing suspend file %s\n",f);
> + 	 unlink(f);
> + 	 /* qemu_savevm(f); */
> +       }
> +       else {
> + 	 fprintf(stderr, "Autosaving VM to file %s\n",f);
> + 	 qemu_savevm(f);
> +       }
> +    }
> +#endif
> +
>      quit_timers();
>      return 0;
>  }
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