The SMMU has a single ASID space, the union of shared and private ASID
sets. This means that the SMMU driver competes with the arch allocator
for ASIDs. Shared ASIDs are those of Linux processes, allocated by the
arch, and contribute in broadcast TLB maintenance. Private ASIDs are
allocated by the SMMU driver and used for "classic" map/unmap DMA. They
require command-queue TLB invalidations.
When we pin down an mm_context and get an ASID that is already in use by
the SMMU, it belongs to a private context. We used to simply abort the
bind, but this is unfair to users that would be unable to bind a few
seemingly random processes. Try to allocate a new private ASID for the
context, and make the old ASID shared.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20200918101852.582559-10-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
With Shared Virtual Addressing (SVA), we need to mirror CPU TTBR, TCR,
MAIR and ASIDs in SMMU contexts. Each SMMU has a single ASID space split
into two sets, shared and private. Shared ASIDs correspond to those
obtained from the arch ASID allocator, and private ASIDs are used for
"classic" map/unmap DMA.
A possible conflict happens when trying to use a shared ASID that has
already been allocated for private use by the SMMU driver. This will be
addressed in a later patch by replacing the private ASID. At the
moment we return -EBUSY.
Each mm_struct shared with the SMMU will have a single context
descriptor. Add a refcount to keep track of this. It will be protected
by the global SVA lock.
Introduce a new arm-smmu-v3-sva.c file and the CONFIG_ARM_SMMU_V3_SVA
option to let users opt in SVA support.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20200918101852.582559-9-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
