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

[Eduardo Habkost]

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 <address@hidden>
> ---
>  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.


> +
>  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);
}

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