Messages in this thread | | | From | Ard Biesheuvel <> | Date | Thu, 4 Nov 2021 09:57:04 +0100 | Subject | Re: [PATCH v2] dma-direct: improve DMA_ATTR_NO_KERNEL_MAPPING |
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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.
And you still haven't explained what the actual problem is: is this about CPU speculation corrupting non-cache coherent inbound DMA?
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