[RFC,qemu,v3,4/4] spapr/iommu: Enable in-kernel TCE acceleration via VFIO KVM device

This uses new kernel KVM_CAP_SPAPR_TCE_VFIO capability to enable
in-kernel acceleration of TCE update requests which will go via
the VFIO KVM device.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 target/ppc/kvm_ppc.h | 6 ++++++
 hw/ppc/spapr_iommu.c | 4 ++++
 target/ppc/kvm.c     | 7 ++++++-
 3 files changed, 16 insertions(+), 1 deletion(-)

On Sat, Apr 01, 2017 at 11:37:41PM +1100, Alexey Kardashevskiy wrote:
> This uses new kernel KVM_CAP_SPAPR_TCE_VFIO capability to enable
> in-kernel acceleration of TCE update requests which will go via
> the VFIO KVM device.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  target/ppc/kvm_ppc.h | 6 ++++++
>  hw/ppc/spapr_iommu.c | 4 ++++
>  target/ppc/kvm.c     | 7 ++++++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
> index f48243d13f..ce7327a4e0 100644
> --- a/target/ppc/kvm_ppc.h
> +++ b/target/ppc/kvm_ppc.h
> @@ -46,6 +46,7 @@ void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t page_shift,
>  int kvmppc_remove_spapr_tce(void *table, int pfd, uint32_t window_size);
>  int kvmppc_reset_htab(int shift_hint);
>  uint64_t kvmppc_rma_size(uint64_t current_size, unsigned int hash_shift);
> +bool kvmppc_has_cap_spapr_vfio(void);
>  #endif /* !CONFIG_USER_ONLY */
>  bool kvmppc_has_cap_epr(void);
>  int kvmppc_define_rtas_kernel_token(uint32_t token, const char *function);
> @@ -216,6 +217,11 @@ static inline bool kvmppc_is_mem_backend_page_size_ok(char *obj_path)
>      return true;
>  }
>  
> +static inline bool kvmppc_has_cap_spapr_vfio(void)
> +{
> +    return false;
> +}
> +
>  #endif /* !CONFIG_USER_ONLY */
>  
>  static inline bool kvmppc_has_cap_epr(void)
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index f7531a6408..35c2516fcb 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -293,6 +293,10 @@ void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool need_vfio)
>  
>      tcet->need_vfio = need_vfio;
>  
> +    if (!need_vfio || (tcet->fd != -1 && kvmppc_has_cap_spapr_vfio())) {
> +        return;
> +    }
> +
>      oldtable = tcet->table;
>  
>      tcet->table = spapr_tce_alloc_table(tcet->liobn,
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 20f07ff320..76bd92c663 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -132,7 +132,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      cap_spapr_tce = kvm_check_extension(s, KVM_CAP_SPAPR_TCE);
>      cap_spapr_tce_64 = kvm_check_extension(s, KVM_CAP_SPAPR_TCE_64);
>      cap_spapr_multitce = kvm_check_extension(s, KVM_CAP_SPAPR_MULTITCE);
> -    cap_spapr_vfio = false;
> +    cap_spapr_vfio = kvm_check_extension(s, KVM_CAP_SPAPR_TCE_VFIO);
>      cap_one_reg = kvm_check_extension(s, KVM_CAP_ONE_REG);
>      cap_hior = kvm_check_extension(s, KVM_CAP_PPC_HIOR);
>      cap_epr = kvm_check_extension(s, KVM_CAP_PPC_EPR);
> @@ -2422,6 +2422,11 @@ bool kvmppc_has_cap_mmu_hash_v3(void)
>      return cap_mmu_hash_v3;
>  }
>  
> +bool kvmppc_has_cap_spapr_vfio(void)
> +{
> +    return cap_spapr_vfio;
> +}
> +
>  static PowerPCCPUClass *ppc_cpu_get_family_class(PowerPCCPUClass *pcc)
>  {
>      ObjectClass *oc = OBJECT_CLASS(pcc);