On Thu, Jan 23, 2014 at 02:15:07PM -0500, Nicolas Pitre wrote: > On Wed, 22 Jan 2014, Wang Nan wrote: > > > This patch allows the kernel to be loaded at the middle of kernel awared > > physical memory. Before this patch, users must use mem= or device tree to cheat > > kernel about the start address of physical memory. > > > > This feature is useful in some special cases, for example, building a crash > > dump kernel. Without it, kernel command line, atag and devicetree must be > > adjusted carefully, sometimes is impossible. > > With CONFIG_PATCH_PHYS_VIRT the value for PHYS_OFFSET is determined > dynamically by rounding down the kernel image start address to the > previous 16MB boundary. In the case of a crash kernel, this might be > cleaner to simply readjust __pv_phys_offset during early boot and call > fixup_pv_table(), and then reserve away the memory from the previous > kernel. That will let you access that memory directly (with gdb for > example) and no pointer address translation will be required. We already have support in the kernel to ignore memory below the calculated PHYS_OFFSET. See 571b14375019c3a66ef70d4d4a7083f4238aca30. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>