vfio: Provide module option to disable vfio_iommu_type1 hugepage support

Add a module option to vfio_iommu_type1 to disable IOMMU hugepage
support.  This causes iommu_map to only be called with single page
mappings, disabling the IOMMU driver's ability to use hugepages.
This option can be enabled by loading vfio_iommu_type1 with
disable_hugepages=1 or dynamically through sysfs.  If enabled
dynamically, only new mappings are restricted.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 6654a7eb42d3..8a2be4e40f22 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -48,6 +48,12 @@ module_param_named(allow_unsafe_interrupts,
 MODULE_PARM_DESC(allow_unsafe_interrupts,
                  "Enable VFIO IOMMU support for on platforms without interrupt remapping support.");
 
+static bool disable_hugepages;
+module_param_named(disable_hugepages,
+                   disable_hugepages, bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(disable_hugepages,
+                 "Disable VFIO IOMMU support for IOMMU hugepages.");
+
 struct vfio_iommu {
         struct iommu_domain     *domain;
         struct mutex            lock;
@@ -270,6 +276,11 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
                 return -ENOMEM;
         }
 
+        if (unlikely(disable_hugepages)) {
+                vfio_lock_acct(1);
+                return 1;
+        }
+
         /* Lock all the consecutive pages from pfn_base */
         for (i = 1, vaddr += PAGE_SIZE; i < npage; i++, vaddr += PAGE_SIZE) {
                 unsigned long pfn = 0;