Richard Henderson <r...@twiddle.net> writes: > On 09/12/2016 06:47 AM, Alex Bennée wrote: >>> > + /* Notice an IO access, or a notdirty page. */ >>> > + if (unlikely(tlb_addr & ~TARGET_PAGE_MASK)) { >>> > + /* There's really nothing that can be done to >>> > + support this apart from stop-the-world. */ >>> > + goto stop_the_world; >> We are also triggering on TLB_NOTDIRTY here in the case where a >> conditional write is the first write to a page. I don't know if a >> stop_the_world is required at this point but we will need to ensure we >> clear bits as notdirty_mem_write() does. >> > > You're quite right that we could probably special-case TLB_NOTDIRTY here such > that (1) we needn't leave the cpu loop, and (2) needn't utilize the actual > "write" part of notdirty_mem_write; just set the bits then fall through to the > actual atomic instruction below.
I do hit this case with ppc64, where I see that its the first write to the page and it exits from this every time, causing the kernel to print soft-lockups. Can we add the special case here for NOTDIRTY and set the page as dirty and return successfully? Regards Nikunj