Messages in this thread | | | Date | Thu, 23 Sep 2004 20:29:28 -0700 | From | William Lee Irwin III <> | Subject | Re: [vm 0/4] replace remap_page_range() with remap_pfn_range() |
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On Thu, Sep 23, 2004 at 06:22:22PM -0500, John Fusco wrote: >> Everything worked great until we decided that we needed to install 6GB >> in this system. The problem is that remap_page_range() uses an unsigned >> long as the parameter for a physical address. On IA32, an unsigned long >> is 32-bits, but the IA32 is capable of addressing well over 4GB of RAM. >> So physical addresses on IA32 must be larger than 32 bits.
On Thu, Sep 23, 2004 at 07:17:35PM -0700, William Lee Irwin III wrote: > Do these patches work for you? Compiletested on sparc64.
Long-format changelog:
Resolve physical address overflow issue in the remap_page_range() API by replacing it with remap_pfn_range(), which accepts its physical address argument as a pfn, hence allowing the use of a single-precision physical address argument without the risk of overflow at the API boundary. The above issue has hobbled support for various 32-bit architectures, including some embedded systems (ppc440 IIRC), caused persistent portability issues for sound drivers for legacy systems (sparc32; unfortunately this patch alone does not fully resolve those), and according to John Fusco's reports, made drivers for some PCI-X hardware infeasible to port to recent ia32 PAE enterprise systems. With this patch series applied, physical address overflows on 32-bit systems caused directly by remap_page_range() are gone forever, and ca. 100LOC of cut-and-waste driver code are swept out of existence alongside them.
-- wli
P.S.: The existing solution to the sparc32 issue was to pass a double precision representation of the physical address as 2 single- precision arguments in an API (io_remap_page_range()) whose argument corresponding to those two was a single single- precision argument on most/all other architectures. The sparc32-specific issue requires more work beyond these patches to rectify. The most apparent consequence of the API skew is that drivers don't compile on sparc32 when they use io_remap_page_range() due to passing insufficient arguments, or vice-versa for drivers originally written for sparc32. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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