32784a9562
The sva_bind() function allows devices to access process address spaces
using a PASID (aka SSID).
(1) bind() allocates or gets an existing MMU notifier tied to the
(domain, mm) pair. Each mm gets one PASID.
(2) Any change to the address space calls invalidate_range() which sends
ATC invalidations (in a subsequent patch).
(3) When the process address space dies, the release() notifier disables
the CD to allow reclaiming the page tables. Since release() has to
be light we do not instruct device drivers to stop DMA here, we just
ignore incoming page faults from this point onwards.
To avoid any event 0x0a print (C_BAD_CD) we disable translation
without clearing CD.V. PCIe Translation Requests and Page Requests
are silently denied. Don't clear the R bit because the S bit can't
be cleared when STALL_MODEL==0b10 (forced), and clearing R without
clearing S is useless. Faulting transactions will stall and will be
aborted by the IOPF handler.
(4) After stopping DMA, the device driver releases the bond by calling
unbind(). We release the MMU notifier, free the PASID and the bond.
Three structures keep track of bonds:
* arm_smmu_bond: one per {device, mm} pair, the handle returned to the
device driver for a bind() request.
* arm_smmu_mmu_notifier: one per {domain, mm} pair, deals with ATS/TLB
invalidations and clearing the context descriptor on mm exit.
* arm_smmu_ctx_desc: one per mm, holds the pinned ASID and pgd.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20201106155048.997886-4-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
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.