On Thu, Jun 08, 2017 at 07:35:28AM +0200, Martin Schwidefsky wrote: > On Wed, 7 Jun 2017 22:47:56 +0200 > Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote: > > On Wed, Jun 07, 2017 at 02:34:40PM +0200, Martin Schwidefsky wrote: > > > +#define arch_elf_pt_proc(ehdr, phdr, elf, interp, state) \ > > > +({ \ > > > + struct elf64_hdr *_ehdr = (void *) ehdr; \ > > > + struct elf64_phdr *_phdr = (void *) phdr; \ > > > + int _rc = 0; \ > > > + if (_ehdr->e_ident[EI_CLASS] == ELFCLASS64 && \ > > > + _phdr->p_type == PT_S390_REQUEST_PGSTE && \ > > > + !page_table_allocate_pgste && \ > > > + !test_thread_flag(TIF_REQUEST_PGSTE)) { \ > > > + set_thread_flag(TIF_REQUEST_PGSTE); \ > > > + set_pt_regs_flag(task_pt_regs(current), \ > > > + PIF_SYSCALL_RESTART); \ > > > + _rc = -EAGAIN; \ > > > + } \ > > > + _rc; \ > > > +}) > > > > I'm wondering if this should simply fail, if a PT_S390_REQUEST_PGSTE type > > segment exists, but it is not ELFCLASS64? > > It will fail later anyway on s390_enable_sie(), but... > > Does it matter if it fails for a 32-bit ELF file? Just makes the code more > complex without benefit, no? It would be more consistent, since right now a 32-bit ELF file with PT_S390_REQUEST_PGSTE will be exectuted, but the page tables won't have any pgstes. That's sort of odd, isn't it? And that later on it won't be able to create a virtual machine because our current implementation doesn't allow that for compat tasks is sort of unrelated. But anyway, I'll leave that up to you, it doesn't really matter. > > > > diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h > > > index c119d564d8f2..1201b18e817d 100644 > > > --- a/arch/s390/include/asm/mmu_context.h > > > +++ b/arch/s390/include/asm/mmu_context.h > > > @@ -25,7 +25,8 @@ static inline int init_new_context(struct task_struct *tsk, > > > mm->context.gmap_asce = 0; > > > mm->context.flush_mm = 0; > > > #ifdef CONFIG_PGSTE > > > - mm->context.alloc_pgste = page_table_allocate_pgste; > > > + mm->context.alloc_pgste = page_table_allocate_pgste || > > > + test_thread_flag(TIF_REQUEST_PGSTE); > > > > I think the alloc_pgste flag should be inherited on fork, no? > > Yes, that makes it more consistent. I'll add it. By the way, what prevents with the _current_ code a scenario like: - set allocate_pgste sysctl to 1 - create kvm guest - s390_enable_sie - run vcpu - set allocate_pgste sysctl to 0 - clone(... CLONE_FILES ...) (that is: new mm without pgstes, but shared fds) - [child] run vcpu Is there anything that makes sure we cannot execute the sie instruction in the child process?