327d5b2fee
Currently, if a 32bit device initially uses an identity domain, Intel IOMMU driver will convert it forcibly to a DMA one if its address capability is not enough for the whole system memory. The motivation was to overcome the overhead caused by possible bounced buffer. Unfortunately, this improvement has led to many problems. For example, some 32bit devices are required to use an identity domain, forcing them to use DMA domain will cause the device not to work anymore. On the other hand, the VMD sub-devices share a domain but each sub-device might have different address capability. Forcing a VMD sub-device to use DMA domain blindly will impact the operation of other sub-devices without any notification. Further more, PCI aliased devices (PCI bridge and all devices beneath it, VMD devices and various devices quirked with pci_add_dma_alias()) must use the same domain. Forcing one device to switch to DMA domain during runtime will cause in-fligh DMAs for other devices to abort or target to other memory which might cause undefind system behavior. With the last private domain usage in iommu_need_mapping() removed, all private domain helpers are also cleaned in this patch. Otherwise, the compiler will complain that some functions are defined but not used. Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Tested-by: Daniel Drake <drake@endlessm.com> Reviewed-by: Jon Derrick <jonathan.derrick@intel.com> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com> Cc: Daniel Drake <drake@endlessm.com> Cc: Derrick Jonathan <jonathan.derrick@intel.com> Cc: Jerry Snitselaar <jsnitsel@redhat.com> Link: https://lore.kernel.org/r/20200506015947.28662-2-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.