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    SubjectRe: [PATCH v2] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel
    On Wed, Apr 03, 2019 at 04:23:06PM +0800, Chao Fan wrote:
    >On Wed, Apr 03, 2019 at 04:09:16PM +0800, Dave Young wrote:
    >>On 04/03/19 at 03:21pm, Chao Fan wrote:
    >>> On Wed, Apr 03, 2019 at 01:53:40PM +0800, Dave Young wrote:
    >>> >On 04/03/19 at 01:35pm, Chao Fan wrote:
    >>> >> On Tue, Apr 02, 2019 at 08:03:19PM +0800, Dave Young wrote:
    >>> >> >On 04/01/19 at 12:08am, Junichi Nomura wrote:
    [...]
    >>> >
    >>> >It is weird to me. Probably I need find out why I can not reproduce the
    >>> >bug this patch is addressing first.
    >>>
    >>> Hmm, is your laptop booted from EFI or legacy BIOS?
    >>
    >>EFI booted.
    >>
    >>> >
    >>> >earlyprintk seems not working for me anymore, it is not easy to debug on
    >>> >laptop now.
    >>>
    >>> Another computer can help print the console message.
    >>> I remeber you are good at debug on two computers.
    >>
    >>I used to use earlyprintk, but seems earlyprintk can not work so early.
    >>So I only can try to comment out code manually.
    >
    >Ah, I got it. If you want to use earlyprintk to print message of
    >get_rsdp_addr(), you should change some code.
    >Because get_rsdp_addr() is called before earlyprintk initialed.
    >
    >I am still testing, but in my debug stage, I change like this:
    >diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
    >index c0d6c560df69..dbbe8d9a5792 100644
    >--- a/arch/x86/boot/compressed/misc.c
    >+++ b/arch/x86/boot/compressed/misc.c
    >@@ -352,7 +352,6 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
    > boot_params->hdr.loadflags &= ~KASLR_FLAG;
    >
    > /* Save RSDP address for later use. */
    >- boot_params->acpi_rsdp_addr = get_rsdp_addr();
    >
    > sanitize_boot_params(boot_params);
    >
    >@@ -368,6 +367,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
    > cols = boot_params->screen_info.orig_video_cols;
    >
    > console_init();
    >+ boot_params->acpi_rsdp_addr = get_rsdp_addr();
    > debug_putstr("early console in extract_kernel\n");
    >
    > free_mem_ptr = heap; /* Heap */
    >
    >Call this function after console_init().
    >That will make earlyprintk works.
    >
    >>
    >>It seems to be still some bug in early acpi code because if I
    >>return 0 in get rsdp function it just works.
    >>
    >>This guess make sense to me for now:
    >>1. nokaslr does not work because it may only avoid randomization, but it
    >>does not avoid running the early acpi parsing code.
    >>
    >>2. kexec does not work without the patch we talked about, because I just
    >>reproduced Junichi reported bug, sometimes hang, or reset, it is
    >>understandable.
    >>
    >>3. kexec does not work with the patch, so there is still bugs in the
    >>code.
    >>
    >>So several things to do is:
    >>
    >>Fix 1. (separate issue), Baoquan or either of you may want to fix it :)
    >
    >For 1, I think it's not needed to fix. Since not only KASLR needs RSDP.
    >So nokaslr should not stop the acpi parsing code.
    >>
    >>Fix 3. need more debugging, have you or Junichi run tests on more real
    >>hardware, maybe it is easier to reproduce on real hardware, I'm glad to
    >>help to try test patch or provide any help.
    >
    >I am still testing in real hardware.

    Hi Dave,

    I find a Fujitsu Desktop PC to test it.
    Without this PATCH, it failed to kexec and kdump.
    With this PATCH, it succeed to kexec.
    But failed to kdump. From the log, I think it didn't jump to the second
    kernel, just reboot after panic. I have not figured out what's the
    problem, but it seems not caused by this PATCH.
    So I still think this PATCH works for the Fujitsu Desktop PC.

    As for your issue, I think there may be some problems related to specified
    hardware. Are you using a Lenovo laptop?

    And I am not sure how Nomura tested it.

    Thanks,
    Chao Fan

    >
    >Thanks,
    >Chao Fan
    >
    >>
    >>Thanks
    >>Dave
    >>
    >>


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