On 05.01.2012, at 10:54, Christian Borntraeger wrote:
> The prefix register is a read-mostly value that is necessary to emulate
> memory accesses on behalf of the guest cpu in an architecture compliant
> way. Avoid an additional ioctl by providing the prefix content in the
> r/o section of kvm_run.
>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
> arch/s390/include/asm/kvm.h | 2 ++
> arch/s390/kvm/kvm-s390.c | 3 +++
> 2 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm.h b/arch/s390/include/asm/kvm.h
> index dda27a0..b48edc3 100644
> --- a/arch/s390/include/asm/kvm.h
> +++ b/arch/s390/include/asm/kvm.h
> @@ -41,8 +41,10 @@ struct kvm_debug_exit_arch {
> struct kvm_guest_debug_arch {
> };
>
> +#define KVM_SYNC_RO_PREFIX (1UL << 0)
> /* definition of registers in kvm_run */
> struct kvm_sync_ro_regs {
> + __u32 prefix; /* prefix register */
Yes, the prefix register is 32 bits today, but it doesn't have to stay that way. Why not just make it a u64?
Alex
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