Messages in this thread | | | Date | Mon, 4 Jul 2022 11:35:23 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation |
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On Sat, Jul 02, 2022 at 11:57:53PM +0800, Guanghui Feng wrote: > The arm64 can build 2M/1G block/sectiion mapping. When using DMA/DMA32 zone > (enable crashkernel, disable rodata full, disable kfence), the mem_map will > use non block/section mapping(for crashkernel requires to shrink the region > in page granularity). But it will degrade performance when doing larging > continuous mem access in kernel(memcpy/memmove, etc).
Hmm. It seems a bit silly to me that we take special care to unmap the crashkernel from the linear map even when can_set_direct_map() is false, as we won't be protecting the main kernel at all!
Why don't we just leave the crashkernel mapped if !can_set_direct_map() and then this problem just goes away?
Will
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