From: Paul Mackerras This patch is from Will Schmidt , with some extra comments from me. On iSeries and on POWER5 machines, there is a data structure which is used for communication between the hypervisor and the kernel, called the `lppaca'. The kernel tells the hypervisor where it is, and the hypervisor requires that it doesn't cross a page boundary. With other changes in the last few months we have ended up with a situation where it could cross a page boundary. This patch increases the alignment requirement for the struct to make sure that it can't cross a page boundary. This is a bug fix and should go into 2.6.10. Signed-off-by: Will Schmidt Signed-off-by: Paul Mackerras Signed-off-by: Andrew Morton --- 25-akpm/include/asm-ppc64/paca.h | 12 +++++++++--- 1 files changed, 9 insertions(+), 3 deletions(-) diff -puN include/asm-ppc64/paca.h~ppc64-make-sure-lppaca-doesnt-cross-page-boundary include/asm-ppc64/paca.h --- 25/include/asm-ppc64/paca.h~ppc64-make-sure-lppaca-doesnt-cross-page-boundary 2004-12-12 20:12:30.263328280 -0800 +++ 25-akpm/include/asm-ppc64/paca.h 2004-12-12 20:12:30.273326760 -0800 @@ -99,11 +99,17 @@ struct paca_struct { u64 exdsi[8]; /* used for linear mapping hash table misses */ /* - * iSeries structues which the hypervisor knows about - Not - * sure if these particularly need to be cacheline aligned. + * iSeries structure which the hypervisor knows about - + * this structure should not cross a page boundary. + * The vpa_init/register_vpa call is now known to fail if the + * lppaca structure crosses a page boundary. * The lppaca is also used on POWER5 pSeries boxes. + * The lppaca is 640 bytes long, and cannot readily change + * since the hypervisor knows its layout, so a 1kB + * alignment will suffice to ensure that it doesn't + * cross a page boundary. */ - struct ItLpPaca lppaca __attribute__((aligned(0x80))); + struct ItLpPaca lppaca __attribute__((__aligned__(0x400))); #ifdef CONFIG_PPC_ISERIES struct ItLpRegSave reg_save; #endif _