Subject: Re: [PATCH -V3 2/4] powerpc/kvm: Contiguous memory allocator based hash page table allocation

From: Alexander Graf <[email-masked]>
Date: Tue, 02 Jul 2013 17:12:23 +0200

On 07/02/2013 07:45 AM, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V"<[email-masked]>
>
> Powerpc architecture uses a hash based page table mechanism for mapping virtual
> addresses to physical address. The architecture require this hash page table to
> be physically contiguous. With KVM on Powerpc currently we use early reservation
> mechanism for allocating guest hash page table. This implies that we need to
> reserve a big memory region to ensure we can create large number of guest
> simultaneously with KVM on Power. Another disadvantage is that the reserved memory
> is not available to rest of the subsystems and and that implies we limit the total
> available memory in the host.
>
> This patch series switch the guest hash page table allocation to use
> contiguous memory allocator.
>
> Signed-off-by: Aneesh Kumar K.V<[email-masked]>

Is CMA a mandatory option in the kernel? Or can it be optionally 
disabled? If it can be disabled, we should keep the preallocated 
fallback case around for systems that have CMA disabled.

Alex