I'm having some problems with activating swap partitions when using a 64 bit kernel on a 32 bit userland. I think I know what the problem is. The structure of the swap devices is that the first 4096 bytes contains a bitmap. Bits that have been set indicate that the page of memory for which the number in the swap space matches the offset of the bit at the start of the space is available for paging. The problem is then these bits are being checked, through the test_bit function call, where we read 64 bit at a time, and they where written 32 bit at a time (from the 32 bit kernel). Note: we are talking about a bigendian system. A little example to illustrate that I mean: Set bit 0-53 to 1 and clear bit 54-63 (stored with 32 bit access) ADDR = 0xffffffff; ADDR+4 = 0x003fffff; If I read it as two 32 bit words I get the same result (bit 0-53 is set), but if I read it as one 64 bit double-word I get. ADDR = 0xffffffff0003ffff; Now bit 0-17 and bit 32-63 is set. The bottom line is that I don't think we can make the address 64 bit aligned in the "set/clear-and-test" functions in include/asm-mips64/bitops.h, without hurting a lot of drivers which use these functions to operate on hw-defined data-structures. /Carsten -- _ _ ____ ___ Carsten Langgaard Mailto:carstenl@mips.com |\ /|||___)(___ MIPS Denmark Direct: +45 4486 5527 | \/ ||| ____) Lautrupvang 4B Switch: +45 4486 5555 TECHNOLOGIES 2750 Ballerup Fax...: +45 4486 5556 Denmark http://www.mips.com
