Re: [PATCH v8 09/15] ARM: KVM: Memory virtualization setup

[Marcelo Tosatti <mtosatti@redhat.com>]

On Fri, Jun 15, 2012 at 03:08:22PM -0400, Christoffer Dall wrote:
> From: Christoffer Dall <cdall@cs.columbia.edu>
> 
> This commit introduces the framework for guest memory management
> through the use of 2nd stage translation. Each VM has a pointer
> to a level-1 table (the pgd field in struct kvm_arch) which is
> used for the 2nd stage translations. Entries are added when handling
> guest faults (later patch) and the table itself can be allocated and
> freed through the following functions implemented in
> arch/arm/kvm/arm_mmu.c:
>  - kvm_alloc_stage2_pgd(struct kvm *kvm);
>  - kvm_free_stage2_pgd(struct kvm *kvm);
> 
> Further, each entry in TLBs and caches are tagged with a VMID
> identifier in addition to ASIDs. The VMIDs are assigned consecutively
> to VMs in the order that VMs are executed, and caches and tlbs are
> invalidated when the VMID space has been used to allow for more than
> 255 simultaenously running guests.
> 
> The 2nd stage pgd is allocated in kvm_arch_init_vm(). The table is
> freed in kvm_arch_destroy_vm(). Both functions are called from the main
> KVM code.
> 
> Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

Can you explain on a high level how the IPA -> PA mappings work?