Messages in this thread | | | Subject | Re: [PATCH v2] dma-direct: improve DMA_ATTR_NO_KERNEL_MAPPING | From | Walter Wu <> | Date | Thu, 4 Nov 2021 20:31:00 +0800 |
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On Thu, 2021-11-04 at 09:57 +0100, Ard Biesheuvel wrote: > On Thu, 4 Nov 2021 at 09:53, Christoph Hellwig <hch@lst.de> wrote: > > > > On Thu, Nov 04, 2021 at 10:32:21AM +0800, Walter Wu wrote: > > > diff --git a/include/linux/set_memory.h > > > b/include/linux/set_memory.h > > > index f36be5166c19..6c7d1683339c 100644 > > > --- a/include/linux/set_memory.h > > > +++ b/include/linux/set_memory.h > > > @@ -7,11 +7,16 @@ > > > > > > #ifdef CONFIG_ARCH_HAS_SET_MEMORY > > > #include <asm/set_memory.h> > > > + > > > +#ifndef CONFIG_RODATA_FULL_DEFAULT_ENABLED > > > > This is an arm64-specific symbol, and one that only controls a > > default. I don't think it is suitable to key off stubs in common > > code. > > > > > +static inline int set_memory_valid(unsigned long addr, int > > > numpages, int enable) { return 0; } > > > > Pleae avoid overly long lines. > > > > > + if (IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED)) > > > { > > > + kaddr = (unsigned > > > long)phys_to_virt(dma_to_phys(dev, *dma_handle)); > > > > This can just use page_address. > > > > > + /* page remove kernel mapping for arm64 */ > > > + set_memory_valid(kaddr, size >> PAGE_SHIFT, > > > 0); > > > + } > > > > But more importantly: set_memory_valid only exists on arm64, this > > will break compile everywhere else. And this API is complete crap. > > Passing kernel virtual addresses as unsigned long just sucks, and > > passing an integer argument for valid/non-valid also is a horrible > > API. > > > > ... and as I pointed out before, you can still pass rodata=off on > arm64, and get the old behavior, in which case bad things will happen > if you try to use an API that expects to operate on page mappings > with > a 1 GB block mapping. >
Thanks for your suggestion.
> And you still haven't explained what the actual problem is: is this > about CPU speculation corrupting non-cache coherent inbound DMA?
No corrupiton, only cpu read it, we hope to fix the behavior.
Thanks. Walter
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