Re: [Qemu-arm] [Qemu-devel] [PATCH v2 6/6] hw/arm/virt: Set minimum_page_bits to 12

[Andrew Jones]

On Tue, Jun 21, 2016 at 06:09:34PM +0100, Peter Maydell wrote:
> Since the virt board model will never create a CPU which is
> pre-ARMv7, we know that our minimum page size is 4K and can
> set minimum_page_bits accordingly, for improved performance.
> 
> Note that this is a migration compatibility break.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  hw/arm/virt.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index c5c125e..f9b51aa 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1440,6 +1440,8 @@ static void virt_machine_class_init(ObjectClass *oc, 
> void *data)
>      mc->block_default_type = IF_VIRTIO;
>      mc->no_cdrom = 1;
>      mc->pci_allow_0_address = true;
> +    /* We know we will never create a pre-ARMv7 CPU which needs 1K pages */
> +    mc->minimum_page_bits = 12;
>  }

As this breaks migration, then I guess we also need

@@ -1507,5 +1510,6 @@ static void virt_machine_2_6_options(MachineClass *mc)
 {
     virt_machine_2_7_options(mc);
     SET_MACHINE_COMPAT(mc, VIRT_COMPAT_2_6);
+    mc->minimum_page_bits = 10;
 }
 DEFINE_VIRT_MACHINE(2, 6)

>  
>  static const TypeInfo virt_machine_info = {
> -- 
> 1.9.1
> 
>