Re: [Qemu-devel] [RFC PATCH v2 02/13] spapr_iommu: Disable in-kernel IOMMU tables for >4GB windows

[Alexander Graf <agraf@suse.de>]

On 15.08.14 12:12, Alexey Kardashevskiy wrote:
> The existing KVM_CREATE_SPAPR_TCE ioctl only support 4G windows max.
> We are going to add huge DMA windows support so this will create small
> window and unexpectedly fail later.
> 
> This disables KVM_CREATE_SPAPR_TCE for windows bigger that 4GB. Since
> those windows are normally mapped at the boot time, there will be no
> performance impact.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>  hw/ppc/spapr_iommu.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index f6e32a4..36f5d27 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -113,11 +113,11 @@ static MemoryRegionIOMMUOps spapr_iommu_ops = {
>  static int spapr_tce_table_realize(DeviceState *dev)
>  {
>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(dev);
> +    uint64_t window_size = tcet->nb_table << tcet->page_shift;
>  
> -    if (kvm_enabled()) {
> +    if (kvm_enabled() && !(window_size >> 32)) {

Please add a comment here that explains the reasoning.


Alex