On Wed, 14 Oct, at 04:29:33PM, Paolo Bonzini wrote: > > On 14/10/2015 15:52, Matt Fleming wrote: > >> > However, for non-PAE kernels there is no guarantee that the identity > >> > mapping in the initial_page_table extends as far as the GDT; in this > >> > case, accesses to the GDT will cause a page fault (which quickly becomes > >> > a triple fault). Fix this by copying the kernel mappings from > >> > swapper_pg_dir to initial_page_table twice, both at PAGE_OFFSET and at > >> > identity mapping. > > > > Oops, good catch guys. This is clearly a bug, but... > > > > ... I'm a little surprised you managed to trigger this at all, because > > the GDT we load in efi_call_phys_prolog() is part of the per-cpu data > > section and therefore part of the kernel image. > > Only until setup_percpu, which is earlier than SetVirtualAddressMap. > For example, I get: > > setup_percpu: NR_CPUS:8 nr_cpumask_bits:8 nr_cpu_ids:1 nr_node_ids:1 > PERCPU: Embedded 18 pages/cpu @c728e000 s41800 r0 d31928 u73728 > ^^^^^^^ > but the kernel image ends at 0x037fffff. > > The GDT is 0xc728e000 in this run, so the GDT is at the beginning of the > relocated percpu area. Ah, good point. I completely missed that the percpu sections get relocated. -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
