From a905ad043f32bbb0c35d4325036397f20f30c8a9 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Wed, 4 May 2022 16:14:43 -0300 Subject: vfio: Change vfio_external_check_extension() to vfio_file_enforced_coherent() Instead of a general extension check change the function into a limited test if the iommu_domain has enforced coherency, which is the only thing kvm needs to query. Make the new op self contained by properly refcounting the container before touching it. Reviewed-by: Christoph Hellwig Signed-off-by: Jason Gunthorpe Link: https://lore.kernel.org/r/5-v3-f7729924a7ea+25e33-vfio_kvm_no_group_jgg@nvidia.com Signed-off-by: Alex Williamson --- drivers/vfio/vfio.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) (limited to 'drivers/vfio') diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 4805e18f2272..c2a360437e6c 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -1701,11 +1701,35 @@ struct iommu_group *vfio_file_iommu_group(struct file *file) } EXPORT_SYMBOL_GPL(vfio_file_iommu_group); -long vfio_external_check_extension(struct vfio_group *group, unsigned long arg) +/** + * vfio_file_enforced_coherent - True if the DMA associated with the VFIO file + * is always CPU cache coherent + * @file: VFIO group file + * + * Enforced coherency means that the IOMMU ignores things like the PCIe no-snoop + * bit in DMA transactions. A return of false indicates that the user has + * rights to access additional instructions such as wbinvd on x86. + */ +bool vfio_file_enforced_coherent(struct file *file) { - return vfio_ioctl_check_extension(group->container, arg); + struct vfio_group *group = file->private_data; + bool ret; + + if (file->f_op != &vfio_group_fops) + return true; + + /* + * Since the coherency state is determined only once a container is + * attached the user must do so before they can prove they have + * permission. + */ + if (vfio_group_add_container_user(group)) + return true; + ret = vfio_ioctl_check_extension(group->container, VFIO_DMA_CC_IOMMU); + vfio_group_try_dissolve_container(group); + return ret; } -EXPORT_SYMBOL_GPL(vfio_external_check_extension); +EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent); /* * Sub-module support -- cgit v1.2.3-71-gd317