On Tue, 19 Apr 2005, Andi Kleen wrote: > On Fri, Apr 15, 2005 at 06:58:20PM +0100, Hugh Dickins wrote: > > > > I must confess, with all due respect to Andi, that I don't understand his > > dismissal of the possibility that load_cr3 in leave_mm might be the fix > > (to create_elf_tables writing user stack data into the pmd). > > Sorry for the late answer.
Not at all. I didn't expect you to persist in trying to persuade me, thank you for doing so, and I apologize for taking your time on this. > Ok, lets try again. The hole fixed by this patch only covers > the case of an kernel thread with lazy mm doing some memory access > (or more likely the CPU doing a prefetch there). But ELF loading > never happens in lazy mm kernel threads.AFAIK in a "real" process > the TLB is always fully consistent. > > Does that explanation satisfy you? It does. Well, I needed to restudy exec_mmap and switch_mm in detail, and having done so, I agree that the only way you can get through exec_mmap's activate_mm without fully flushing the cpu's TLB, is if the active_mm matches the newly allocated mm (itself impossible since there's a reference on the active_mm), and the cpu bit is still set in cpu_vm_mask - precisely not the case if we went through leave_mm. Yet I was claiming your leave_mm fix could flush TLB for exec_mmap where it wasn't already done. Sorry for letting the neatness of my pmd/stack story blind me to its impossibility, and for wasting your time. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
