Re: [Qemu-devel] [PATCH] qemu: enable PV EOI for qemu 1.3

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Oct 17, 2012 at 05:03:02PM -0300, Eduardo Habkost wrote:
> On Wed, Oct 17, 2012 at 09:40:59PM +0200, Michael S. Tsirkin wrote:
> > Enable KVM PV EOI by default. You can still disable it with
> > -kvm_pv_eoi cpu flag. To avoid breaking cross-version migration,
> > enable only for qemu 1.3 or newer machine type.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  hw/pc.h           |  2 ++
> >  hw/pc_piix.c      | 14 +++++++++++++-
> >  target-i386/cpu.c | 15 +++++++++++++++
> >  3 files changed, 30 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/pc.h b/hw/pc.h
> > index 9923d96..344a545 100644
> > --- a/hw/pc.h
> > +++ b/hw/pc.h
> > @@ -210,4 +210,6 @@ void pc_system_firmware_init(MemoryRegion *rom_memory);
> >  
> >  int e820_add_entry(uint64_t, uint64_t, uint32_t);
> >  
> > +void enable_kvm_pv_eoi(void);
> > +
> >  #endif
> > diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> > index 82364ab..9d4cf48 100644
> > --- a/hw/pc_piix.c
> > +++ b/hw/pc_piix.c
> > @@ -301,6 +301,18 @@ static void pc_init_pci(ram_addr_t ram_size,
> >               initrd_filename, cpu_model, 1, 1);
> >  }
> >  
> > +static void pc_init_pci_pv_eoi(ram_addr_t ram_size,
> > +                               const char *boot_device,
> > +                               const char *kernel_filename,
> > +                               const char *kernel_cmdline,
> > +                               const char *initrd_filename,
> > +                               const char *cpu_model)
> > +{
> > +    enable_kvm_pv_eoi();
> > +    pc_init_pci(ram_size, boot_device, kernel_filename,
> > +		kernel_cmdline, initrd_filename, cpu_model);
> > +}
> 
> Maybe it's better to name it pc_init_pci_1_3() (or something like that)?
> I plan to submit a bug fix (unrelated to PV EOI) that will require using
> a separate init function for the pc-1.3 machine type too, so pv_eoi
> won't be the only difference between pc-1.2 and pc-1.3.
> 

1.4 will need to enable it too.
I'l rename pc_init_pci as pc_init_pci_1_2 instead.

> > +
> >  static void pc_init_pci_no_kvmclock(ram_addr_t ram_size,
> >                                      const char *boot_device,
> >                                      const char *kernel_filename,
> > @@ -353,7 +365,7 @@ static QEMUMachine pc_machine_v1_3 = {
> >      .name = "pc-1.3",
> >      .alias = "pc",
> >      .desc = "Standard PC",
> > -    .init = pc_init_pci,
> > +    .init = pc_init_pci_pv_eoi,
> >      .max_cpus = 255,
> >      .is_default = 1,
> >  };
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index f3708e6..a4a8a02 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -1097,6 +1097,8 @@ static void x86_cpuid_set_tsc_freq(Object *obj, Visitor *v, void *opaque,
> >      cpu->env.tsc_khz = value / 1000;
> >  }
> >  
> > +static bool kvm_pv_eoi_enabled;
> 
> Maybe we can do this as:
> 
> static int default_kvm_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
>                                   (1 << KVM_FEATURE_NOP_IO_DELAY) |
>                                   (1 << KVM_FEATURE_MMU_OP) |
>                                   (1 << KVM_FEATURE_CLOCKSOURCE2) |
>                                   (1 << KVM_FEATURE_ASYNC_PF) |
>                                   (1 << KVM_FEATURE_STEAL_TIME) |
>                                   (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> [...]
> static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
> {
>     [...]
>     plus_kvm_features = default_kvm_features;
>     [...]
> }
> [...]
> void enable_kvm_pv_eoi(void)
> {
>     default_kvm_features = (1UL << KVM_FEATURE_PV_EOI);
> }

How is it better? Also disabling steal time etc for 1.3? Why?

> On either case, the global variable should eventually go away when we
> make CPU objects support global properties. But I still support
> including a solution like this one, as the CPU modelling work is taking
> really long to be finished and I don't think this should hold the
> inclusion of pv_eoi support.
> 
> 
> > +
> >  static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
> >  {
> >      unsigned int i;
> > @@ -1135,6 +1137,8 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
> >          (1 << KVM_FEATURE_ASYNC_PF) | 
> >          (1 << KVM_FEATURE_STEAL_TIME) |
> >          (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> > +    if (kvm_pv_eoi_enabled)
> > +        plus_kvm_features |= (0x1 << KVM_FEATURE_PV_EOI);
> >  #else
> >      plus_kvm_features = 0;
> >  #endif
> > @@ -1953,3 +1957,14 @@ static void x86_cpu_register_types(void)
> >  }
> >  
> >  type_init(x86_cpu_register_types)
> > +
> > +/* Called from hw/pc_piix.c but there is no header
> > + * both files include to put this into.
> > + * Put it here to silence compiler warning.
> > + */
> 
> Why can't pc_piix.c simply include cpu.h?
> 
> > +void enable_kvm_pv_eoi(void);
> > +
> > +void enable_kvm_pv_eoi(void)
> > +{
> > +       kvm_pv_eoi_enabled = true;
> > +}
> > -- 
> > MST
> -- 
> Eduardo