[Qemu-devel] [PATCH 3/2] vfio: Provide module option to disable vfio_iommu_type1 hugepage support

[Alex Williamson]

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 <address@hidden>
---

As suggested by Konrad.  This is cleaner to add as a follow-on

 drivers/vfio/vfio_iommu_type1.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 6654a7e..8a2be4e 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;