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

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Message-ID: <20190403092821.GI1555@localhost.localdomain>
Date:   Wed, 3 Apr 2019 17:28:21 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     "bhe@...hat.com" <bhe@...hat.com>
CC:     Dave Young <dyoung@...hat.com>,
        Junichi Nomura <j-nomura@...jp.nec.com>,
        Borislav Petkov <bp@...en8.de>,
        "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 03:50:15PM +0800, bhe@...hat.com wrote:
>On 04/03/19 at 03:30pm, Chao Fan wrote:
>> On Wed, Apr 03, 2019 at 02:39:11PM +0800, Dave Young wrote:
>> >> Actually I got some different kexec test results.
>> >> 
>> >> Yesterday, with my installed kernel (based on git head several weeks
>> >> ago), kexec kernel panics.
>> >> 
>> >> Then I tried latest mainline with git pull, everything works, (with or
>> >> without the patch, and can not reproduce the bug this patch is fixing)
>> >> 
>> >> Today, test again, kexec reboot hangs (with or without your patch), but
>> >> kdump works always (with or without the patch)
>> >> 
>> >> It is weird to me. Probably I need find out why I can not reproduce the
>> >> bug this patch is addressing first.
>> >> 
>> >> earlyprintk seems not working for me anymore, it is not easy to debug on
>> >> laptop now.
>> >> 
>> >> But the patch itself is clear, I think it should be good.  There might be
>> >> other things broken.
>> >
>> >Disable your immovable mem code then everything works for me.  There
>> >might be something wrong in the code.  Also "nokaslr" does not help, it
>> >should be another problem 
>> 
>> If "nokaslr" doesn't help, so I think
>> >+      /*num_immovable_mem = count_immovable_mem_regions();*/
>> also doesn't help. I think the problem is from get_rsdp_addr().
>
>Yes, seems get_rsdp_addr() has issue in this case. I am wondering if we
>can adjust the postion of get_rsdp_addr() calling. If nokaslr is
>specified, no need to get rsdp?

I think no, RSDP parsing dosn't only work for KASLR.

Thanks,
Chao Fan

>
>> 
>> You test it in your laptop, I only tested in Qemu guest.
>> I have no laptop avaliable, so I will look for a physical machine
>> to test it.
>> 
>> Thanks,
>> Chao Fan
>> 
>> >
>> >diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>> >index 2e53c056ba20..e760c9159662 100644
>> >--- a/arch/x86/boot/compressed/kaslr.c
>> >+++ b/arch/x86/boot/compressed/kaslr.c
>> >@@ -416,7 +416,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>> > 	handle_mem_options();
>> > 
>> > 	/* Enumerate the immovable memory regions */
>> >-	num_immovable_mem = count_immovable_mem_regions();
>> >+	/*num_immovable_mem = count_immovable_mem_regions();*/
>> > 
>> > #ifdef CONFIG_X86_VERBOSE_BOOTUP
>> > 	/* Make sure video RAM can be used. */
>> >diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
>> >index c0d6c560df69..1bc6f46d3aa7 100644
>> >--- a/arch/x86/boot/compressed/misc.c
>> >+++ b/arch/x86/boot/compressed/misc.c
>> >@@ -352,7 +352,7 @@ 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();
>> >+/*	boot_params->acpi_rsdp_addr = get_rsdp_addr(); */
>> > 
>> > 	sanitize_boot_params(boot_params);
>> > 
>> >
>> >
>> 
>> 
>
>