linux-kernel - Re: [PATCH v13 7/8] allower the user to disable pv event support

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Date:	Mon, 04 Mar 2013 10:47:10 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Hu Tao <hutao@...fujitsu.com>
CC:	kvm list <kvm@...r.kernel.org>, qemu-devel <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Gleb Natapov <gleb@...hat.com>,
	Blue Swirl <blauwirbel@...il.com>,
	Eric Blake <eblake@...hat.com>,
	Andrew Jones <drjones@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Anthony Liguori <aliguori@...ibm.com>,
	Markus Armbruster <armbru@...hat.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Juan Quintela <quintela@...hat.com>,
	Orit Wasserman <owasserm@...hat.com>,
	Kevin Wolf <kwolf@...hat.com>,
	Wen Congyang <wency@...fujitsu.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Alexander Graf <agraf@...e.de>,
	Alex Williamson <alex.williamson@...hat.com>,
	Peter Maydell <peter.maydell@...aro.org>
Subject: Re: [PATCH v13 7/8] allower the user to disable pv event support

Il 28/02/2013 13:13, Hu Tao ha scritto:
> Signed-off-by: Wen Congyang <wency@...fujitsu.com>
> Signed-off-by: Hu Tao <hutao@...fujitsu.com>
> ---
>  hw/pc_piix.c    | 9 ++++++++-
>  qemu-options.hx | 3 ++-
>  vl.c            | 4 ++++
>  3 files changed, 14 insertions(+), 2 deletions(-)

We cannot add -machine suboptions for everything we add to a random
machine type.  I think it's better to do one of the following:

1) not add it to the machine by default.  Let libvirt add it with -device.

2) add a property to the piix3 ISA bridges (in hw/piix_pci.c) to
enable/disable it.  It can be set with -global PIIX3.pv_event=on/off.

In the second case, if you set it to on by default, you will also need
to add the property in hw/pc.h, to disable the device in older machine
types for backwards-compatibility.

Paolo

> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 24a9bf3..82a421a 100644
> --- a/hw/pc_piix.c
> +++ b/hw/pc_piix.c
> @@ -44,6 +44,7 @@
>  #include "exec/memory.h"
>  #include "exec/address-spaces.h"
>  #include "cpu.h"
> +#include "qemu/config-file.h"
>  #ifdef CONFIG_XEN
>  #  include <xen/hvm/hvm_info_table.h>
>  #endif
> @@ -86,6 +87,8 @@ static void pc_init1(MemoryRegion *system_memory,
>      MemoryRegion *pci_memory;
>      MemoryRegion *rom_memory;
>      void *fw_cfg = NULL;
> +    QemuOptsList *list = qemu_find_opts("machine");
> +    bool enable_pv_event = false;
>  
>      pc_cpus_init(cpu_model);
>      pc_acpi_init("acpi-dsdt.aml");
> @@ -218,7 +221,11 @@ static void pc_init1(MemoryRegion *system_memory,
>          pc_pci_device_init(pci_bus);
>      }
>  
> -    if (kvm_enabled()) {
> +    if (list && !QTAILQ_EMPTY(&list->head)) {
> +        enable_pv_event = qemu_opt_get_bool(QTAILQ_FIRST(&list->head),
> +                                            "enable_pv_event", false);
> +    }
> +    if (kvm_enabled() && enable_pv_event) {
>          kvm_pv_event_init(isa_bus);
>      }
>  }
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 797d992..1ad4041 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -35,7 +35,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>      "                kernel_irqchip=on|off controls accelerated irqchip support\n"
>      "                kvm_shadow_mem=size of KVM shadow MMU\n"
>      "                dump-guest-core=on|off include guest memory in a core dump (default=on)\n"
> -    "                mem-merge=on|off controls memory merge support (default: on)\n",
> +    "                mem-merge=on|off controls memory merge support (default: on)\n"
> +    "                enable_pv_event=on|off controls pv event support (default: off)\n",
>      QEMU_ARCH_ALL)
>  STEXI
>  @item -machine [type=]@var{name}[,prop=@...{value}[,...]]
> diff --git a/vl.c b/vl.c
> index 51d4922..5b3a279 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -427,6 +427,10 @@ static QemuOptsList qemu_machine_opts = {
>              .name = "usb",
>              .type = QEMU_OPT_BOOL,
>              .help = "Set on/off to enable/disable usb",
> +        }, {
> +            .name = "enable_pv_event",
> +            .type = QEMU_OPT_BOOL,
> +            .help = "handle pv event"
>          },
>          { /* End of list */ }
>      },
> 

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