Re: [PATCH 26/27] Enable 32bit dirty log pointers on 64bit host

[Avi Kivity <avi@redhat.com>]

On 09/29/2009 10:18 AM, Alexander Graf wrote:
> With big endian userspace, we can't quite figure out if a pointer
> is 32 bit (shifted>>  32) or 64 bit when we read a 64 bit pointer.
>
> This is what happens with dirty logging. To get the pointer interpreted
> correctly, I just make it bounce twice, but admittedly that is not ideal.
>
> I'm open for suggestions here.
>
>    

How about adding a new union member to struct kvm_dirty_log:

   __u64 dirty_bitmap_virt;

and deprecate dirty_bitmap.

> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e27b7a9..91c0225 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -720,6 +720,11 @@ int kvm_get_dirty_log(struct kvm *kvm,
>
>   	r = -EFAULT;
>   	if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
> +#ifdef __BIG_ENDIAN
> +		/* Did we get a 32 bit pointer? */
> +		if (copy_to_user((void*)((u64)log->dirty_bitmap>>  32),
> +				 memslot->dirty_bitmap, n))
> +#endif
>   		goto out;
>
>   	if (any)
>    


-- 
error compiling committee.c: too many arguments to function