Jean-Philippe Brucker 48118151d8 arm64: mm: Pin down ASIDs for sharing mm with devices ... To enable address space sharing with the IOMMU, introduce arm64_mm_context_get() and arm64_mm_context_put(), that pin down a context and ensure that it will keep its ASID after a rollover. Export the symbols to let the modular SMMUv3 driver use them. Pinning is necessary because a device constantly needs a valid ASID, unlike tasks that only require one when running. Without pinning, we would need to notify the IOMMU when we're about to use a new ASID for a task, and it would get complicated when a new task is assigned a shared ASID. Consider the following scenario with no ASID pinned: 1. Task t1 is running on CPUx with shared ASID (gen=1, asid=1) 2. Task t2 is scheduled on CPUx, gets ASID (1, 2) 3. Task tn is scheduled on CPUy, a rollover occurs, tn gets ASID (2, 1) We would now have to immediately generate a new ASID for t1, notify the IOMMU, and finally enable task tn. We are holding the lock during all that time, since we can't afford having another CPU trigger a rollover. The IOMMU issues invalidation commands that can take tens of milliseconds. It gets needlessly complicated. All we wanted to do was schedule task tn, that has no business with the IOMMU. By letting the IOMMU pin tasks when needed, we avoid stalling the slow path, and let the pinning fail when we're out of shareable ASIDs. After a rollover, the allocator expects at least one ASID to be available in addition to the reserved ones (one per CPU). So (NR_ASIDS - NR_CPUS - 1) is the maximum number of ASIDs that can be shared with the IOMMU. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Link: https://lore.kernel.org/r/20200918101852.582559-5-jean-philippe@linaro.org Signed-off-by: Will Deacon <will@kernel.org>		2020-09-28 22:15:38 +01:00
..
alpha	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
arc	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
arm	A set of fixes for lockdep, tracing and RCU:	2020-08-30 11:43:50 -07:00
arm64	arm64: mm: Pin down ASIDs for sharing mm with devices	2020-09-28 22:15:38 +01:00
c6x	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
csky	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
h8300	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
hexagon	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
ia64	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
m68k	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
microblaze	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
mips	A set of fixes for lockdep, tracing and RCU:	2020-08-30 11:43:50 -07:00
nds32	A set of fixes for lockdep, tracing and RCU:	2020-08-30 11:43:50 -07:00
nios2	mm/nios2: use general page fault accounting	2020-08-12 10:58:03 -07:00
openrisc	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
parisc	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
powerpc	A set of fixes for lockdep, tracing and RCU:	2020-08-30 11:43:50 -07:00
riscv	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
s390	A set of fixes for lockdep, tracing and RCU:	2020-08-30 11:43:50 -07:00
sh	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
sparc	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
um	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
x86	Three interrupt related fixes for X86:	2020-08-30 12:01:23 -07:00
xtensa	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
.gitignore
Kconfig	A set oftimekeeping/VDSO updates:	2020-08-14 14:26:08 -07:00