Re: [Qemu-devel] [PATCHv2 2/3] target-ppc: Add helpers for updating a CPU's SDR1 and external HPT

[Thomas Huth <thuth@redhat.com>]

On 07.03.2016 03:26, David Gibson wrote:
> When a Power cpu with 64-bit hash MMU has it's hash page table (HPT)
> pointer updated by a write to the SDR1 register we need to update some
> derived variables.  Likewise, when the cpu is configured for an external
> HPT (one not in the guest memory space) some derived variables need to be
> updated.
> 
> Currently the logic for this is (partially) duplicated in ppc_store_sdr1()
> and in spapr_cpu_reset().  In future we're going to need it in some other
> places, so make some common helpers for this update.
> 
> In addition the new ppc_hash64_set_external_hpt() helper also updates
> SDR1 in KVM - it's not updated by the normal runtime KVM <-> qemu CPU
> synchronization.  In a sense this belongs logically in the
> ppc_hash64_set_sdr1() helper, but that is called from
> kvm_arch_get_registers() so can't itself call cpu_synchronize_state()
> without infinite recursion.  In practice this doesn't matter because
> the only other caller is TCG specific.
> 
> Currently there aren't situations where updating SDR1 at runtime in KVM
> matters, but there are going to be in future.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c          | 13 ++-----------
>  target-ppc/kvm.c        |  2 +-
>  target-ppc/kvm_ppc.h    |  6 ++++++
>  target-ppc/mmu-hash64.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  target-ppc/mmu-hash64.h |  6 ++++++
>  target-ppc/mmu_helper.c | 13 ++++++-------
>  6 files changed, 64 insertions(+), 19 deletions(-)

Reviewed-by: Thomas Huth <thuth@redhat.com>