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We added dcache flush on memory add/remove in commitfb5924fddf("powerpc/mm: Flush cache on memory hot(un)plug") to handle crashes on GPU hotplug. Instead of adding dcache flush in generic memory add/remove routine which is used even for regular memory, we should handle these devices specific flush in the device driver code. memtrace did handle this in the driver and that was removed by commit7fd6641de2("powerpc/powernv/memtrace: Let the arch hotunplug code flush cache"). This patch reverts that commit. The dcache flush in memory add was removed by commitea458effa8("powerpc: Don't flush caches when adding memory") which I don't think is correct. The reason why we require dcache flush in memtrace is to make sure we don't have a dirty cache when we remap a pfn to cache inhibited. We should do that when the memtrace module removes the memory and make the pfn available for HTM traces to map it as cache inhibited. The other device mentioned in commitfb5924fddf("powerpc/mm: Flush cache on memory hot(un)plug") is nvlink device with coherent memory. The support for that was removed in commit7eb3cf7619("powerpc/powernv: remove unused NPU DMA code") and commit25b2995a35("mm: remove MEMORY_DEVICE_PUBLIC support") Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210203045812.234439-3-aneesh.kumar@linux.ibm.com
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.