Re: [PATCH v10 02/14] KVM: Cache as_id in kvm_memory_slot

Sean Christopherson
2020-07-02T23:08:54Z

On Mon, Jun 01, 2020 at 07:59:45AM -0400, Peter Xu wrote:
> Cache the address space ID just like the slot ID. It will be used in
> order to fill in the dirty ring entries.
>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> include/linux/kvm_host.h | 1 +
> virt/kvm/kvm_main.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 01276e3d01b9..5e7bbaf7a36b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -346,6 +346,7 @@ struct kvm_memory_slot {
> unsigned long userspace_addr;
> u32 flags;
> short id;
> + u16 as_id;
> };
>
> static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 74bdb7bf3295..ebdd98a30e82 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1243,6 +1243,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> if (!mem->memory_size)
> return kvm_delete_memslot(kvm, mem, &old, as_id);

This technically needs to set as_id in the deleted memslot. I highly doubt
it will ever matter from a functionality perspective, but it'd be confusing
to encounter a memslot whose as_id did not match that of its owner.

> + new.as_id = as_id;
> new.id = id;
> new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
> new.npages = mem->memory_size >> PAGE_SHIFT;
> --
> 2.26.2
>