Re: [PATCH v4 06/14] KVM: ARM: Memory virtualization setup

Christoffer Dall
2012-11-19T15:05:48Z

On Mon, Nov 19, 2012 at 9:53 AM, Will Deacon <will.deacon@arm.com> wrote:
> On Sat, Nov 10, 2012 at 03:42:52PM +0000, Christoffer Dall wrote:
>> 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);
>>
>> 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.
>>
>> We pre-allocate page table memory to be able to synchronize using a
>> spinlock and be called under rcu_read_lock from the MMU notifiers. We
>> steal the mmu_memory_cache implementation from x86 and adapt for our
>> specific usage.
>>
>> We support MMU notifiers (thanks to Marc Zyngier) through
>> kvm_unmap_hva and kvm_set_spte_hva.
>>
>> Finally, define kvm_phys_addr_ioremap() to map a device at a guest IPA,
>> which is used by VGIC support to map the virtual CPU interface registers
>> to the guest. This support is added by Marc Zyngier.
>>
>> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
>
> Modulo my other comments, this patch looks alright to me. I'll go through
> with acks for the next series. In the meantime, I'll just skip over the
> patches that look ok.
>
thanks a lot for the review! I'll be getting back to you on all this
at the end of this week.

-Christoffer