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Date: Mon, 30 Jun 2008 13:51:39 -0600 From: Jonathan Corbet <corbet@....net> To: "Pan, Weimin" <weimin.pan@...com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: Why get_user_pages fails? On Mon, 30 Jun 2008 19:32:41 +0000 "Pan, Weimin" <weimin.pan@...com> wrote: > I booted the kernel and set "mem=512M" and then mmapped the physical > memory above 512M to user space and got the user space virtual > address for that memory. When I passed that address to my driver to > do direct IO. The get_user_pages() in my driver fails. I found that > this is due to the VM_IO and VM_PFNMAP are set. Does that mean the > page structures are not built when I mmapped physical memory to user > space (using remap_pfn_range())? > > Do I have a way to solve this problem? How can I map the physical > memory to user space virtual address and can pass this address to my > driver to do direct IO by using get_user_pages() function? In this situation, you already know where the memory sits in physical space, and there's no point in trying to pin it. So a call to get_user_pages() is entirely unnecessary. You're bypassing the Linux VM, so bypass it entirely. However, this whole scheme seems a little...baroque. Why are you doing things this way? As always in such cases, posting your code can enable others to help you find the right solution to your problem. jon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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