Messages in this thread | | | Date | Mon, 13 Jul 2020 14:06:32 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH 1/3] lib: Add a generic copy_oldmem_page() |
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On Fri, Jul 10, 2020 at 08:55:42PM -0700, Palmer Dabbelt wrote: > +ssize_t copy_oldmem_page(unsigned long pfn, char *buf, > + size_t csize, unsigned long offset, > + int userbuf) > +{ > + void *vaddr; > + > + if (!csize) > + return 0; > + > + vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB); > + if (!vaddr) > + return -ENOMEM;
Doing a memremap for every page is very inefficient. Also I don't see why you'd want to even do that. All memory is in the direct mapping for RISC-V. For other architecture that support highmem kmap_atomic_pfn would do the job, which is what I'd use in a generic version.
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