mirror of https://gitee.com/openkylin/linux.git
77f3445866
When writing a new table entry, we must ensure that the contents of the table is made visible to the SMMU page table walker before the updated table entry itself. This is currently achieved using wmb(), which expands to an expensive and unnecessary DSB instruction. Ideally, we'd just use cmpxchg64_release when writing the table entry, but this doesn't have memory ordering semantics on !SMP systems. Instead, use dma_wmb(), which emits DMB OSHST. Strictly speaking, this does more than we require (since it targets the outer-shareable domain), but it's likely to be significantly faster than the DSB approach. Reported-by: Linu Cherian <linu.cherian@cavium.com> Suggested-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.