[Qemu-devel] [RFC PATCH v3 03/18] spapr_iommu: Disable in-kernel IOMMU tables for >4GB windows

[Alexey Kardashevskiy <aik@ozlabs.ru>]

The existing KVM_CREATE_SPAPR_TCE ioctl only support 4G windows max as
the window size parameter to the kernel ioctl() is 32-bit so
there's no way of expressing a TCE window > 4GB.

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>
---
Changes:
v3:
* fixed commit log
* added cast to uint64_t
---
 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..7f9a862 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 = (uint64_t)tcet->nb_table << tcet->page_shift;
 
-    if (kvm_enabled()) {
+    if (kvm_enabled() && !(window_size >> 32)) {
         tcet->table = kvmppc_create_spapr_tce(tcet->liobn,
-                                              tcet->nb_table <<
-                                              tcet->page_shift,
+                                              window_size,
                                               &tcet->fd,
                                               tcet->vfio_accel);
     }
-- 
2.0.0