linux-kernel - Re: [PATCH v2] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel

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Date:   Wed, 3 Apr 2019 17:02:11 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Dave Young <dyoung@...hat.com>
CC:     Junichi Nomura <j-nomura@...jp.nec.com>,
        Borislav Petkov <bp@...en8.de>,
        "bhe@...hat.com" <bhe@...hat.com>,
        "kasong@...hat.com" <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [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
>>
>>