kvm: iommu: Add cond_resched to legacy device assignment code

When assigning devices to large memory guests (>=128GB guest
memory in the failure case) the functions to create the
IOMMU page-tables for the whole guest might run for a very
long time. On non-preemptible kernels this might cause
Soft-Lockup warnings. Fix these by adding a cond_resched()
to the mapping and unmapping loops.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kvm/iommu.c b/arch/x86/kvm/iommu.c
index 17b73eeac8a4..7dbced309ddb 100644
--- a/arch/x86/kvm/iommu.c
+++ b/arch/x86/kvm/iommu.c
@@ -138,7 +138,7 @@ int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
 
                 gfn += page_size >> PAGE_SHIFT;
 
-
+                cond_resched();
         }
 
         return 0;
@@ -306,6 +306,8 @@ static void kvm_iommu_put_pages(struct kvm *kvm,
                 kvm_unpin_pages(kvm, pfn, unmap_pages);
 
                 gfn += unmap_pages;
+
+                cond_resched();
         }
 }