On 2017-05-08 13:21, Andy Lutomirski wrote: > On Mon, May 8, 2017 at 2:32 AM, Andy Shevchenko > <andy.shevchenko@xxxxxxxxx> wrote: >> On Mon, May 8, 2017 at 9:31 AM, Jan Kiszka <jan.kiszka@xxxxxxxxxxx> wrote: >>> On 2017-03-23 10:14, tip-bot for Andy Lutomirski wrote: >>>> The x86 smpboot trampoline expects initial_page_table to have the >>>> GDT mapped. If the GDT ends up in a virtually mapped per-cpu page, >>>> then it won't be in the page tables at all until perc-pu areas are >>>> set up. The result will be a triple fault the first time that the >>>> CPU attempts to access the GDT after LGDT loads the perc-pu GDT. >>>> >>>> This appears to be an old bug, but somehow the GDT fixmap rework >>>> is triggering it. This seems to have something to do with the >>>> memory layout. >> >>> This breaks the boot on our Intel Quark platform (IOT2000, similar to >>> Galileo Gen2). Reverting it over master makes it work again. Any idea >>> what goes wrong? Let me know how I can help debugging this. >> >> JFYI: As of today linux-next when _kexec:ed_ works fine to me >> >> Perhaps I can test this later with direct boot from SD card. >> > > The most likely explanation is that there's some code that needs the > page table synced and runs before setup_per_cpu_areas(). The relevant > init code is: > > setup_arch(&command_line); > mm_init_cpumask(&init_mm); > setup_command_line(command_line); > setup_nr_cpu_ids(); > setup_per_cpu_areas(); > > so I didn't move it very far. It would be awesome if we could get a > backtrace when the failure happens, but it's likely to be a triple > fault. Is this an EFI boot? I bet the failure is in efi_init(). Yes, it's an EFI thing. Unfortunately, I didn't make earlycon/earlyprintk work yet. > > Could you try reverting just the deletions in the patch? I.e. try a > kernel with both the old and the new copies of the code I moved. Let me try that later. I can also move the new code around to nail down the dependency. Jan -- Siemens AG, Corporate Technology, CT RDA ITP SES-DE Corporate Competence Center Embedded Linux -- 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
