Hi, I'm trying to test some HW that need a large buffer in memory above 4G. I have a dual Opteron PC with 8G RAM and use the boot option "mem=7G" to allow myself to ioremap(0x1C0000000, 0x320000) (allocate 50MB at offset 7G). I am only interested to test this on the amd64 platform, so portability is not an issue, I only intend to test the HW can actually make a DMA into that memory area and that I from userland can mmap it. So far the mmap between the kernel and userland is ok. I use the return value from ioremap as kernel virtual pointer and use the 0x1C0000000 as physical address to the remap_page_range call, e.g.: remap_page_range(vma,vma->vm_start,0x1C000000,PAGE_ALIGN(size),vma->vm_page_ prot); The HW tries to make a DMA transfer to 0x1C000000 but cannot read the test pattern I have put into the area. It just read 0x00 or 0xFF. Here is some pseudo code on what I try to do: ------ code snip ---- pci_enable_device(PciDevice); pci_set_dma_mask(PciDevice, DMA_64BIT_MASK); pci_request_regions(PciDevice, "Test"); pci_set_master(PciDevice); pciBase= ioremap(PciDevice->resource[0].start, ....); InitDevice(pciBase, ....); pVirtualReservedMem = ioremap_nocache(0x000001C0000000ll /* 7GB */, 0x320000 /* 50MB */); memset(pVirtualReservedMem, 0xab, 0x320000); WriteDmaBufferAddressToHW(0x1C0000000); StartHWDmaReadFromDmaBuffer(); ------ code snip end ---- The thing is that the above work if i use a combination of "mem=xx" and ioremap that is below the 4G border. Has anyone an idea on what I'm doing wrong, or is it just a HW bug? Regards, Michael -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
