diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/mm/book3s64/slb.c | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/arch/powerpc/mm/book3s64/slb.c b/arch/powerpc/mm/book3s64/slb.c index c581548b533f..14c62b685f0c 100644 --- a/arch/powerpc/mm/book3s64/slb.c +++ b/arch/powerpc/mm/book3s64/slb.c @@ -825,19 +825,21 @@ long do_slb_fault(struct pt_regs *regs) return -EINVAL; /* - * SLB kernel faults must be very careful not to touch anything - * that is not bolted. E.g., PACA and global variables are okay, - * mm->context stuff is not. - * - * SLB user faults can access all of kernel memory, but must be - * careful not to touch things like IRQ state because it is not - * "reconciled" here. The difficulty is that we must use - * fast_exception_return to return from kernel SLB faults without - * looking at possible non-bolted memory. We could test user vs - * kernel faults in the interrupt handler asm and do a full fault, - * reconcile, ret_from_except for user faults which would make them - * first class kernel code. But for performance it's probably nicer - * if they go via fast_exception_return too. + * SLB kernel faults must be very careful not to touch anything that is + * not bolted. E.g., PACA and global variables are okay, mm->context + * stuff is not. SLB user faults may access all of memory (and induce + * one recursive SLB kernel fault), so the kernel fault must not + * trample on the user fault state at those points. + */ + + /* + * The interrupt state is not reconciled, for performance, so that + * fast_interrupt_return can be used. The handler must not touch local + * irq state, or schedule. We could test for usermode and upgrade to a + * normal process context (synchronous) interrupt for those, which + * would make them first-class kernel code and able to be traced and + * instrumented, although performance would suffer a bit, it would + * probably be a good tradeoff. */ if (id >= LINEAR_MAP_REGION_ID) { long err; |