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

From: Chao Fan <fanc.fnst@cn.fujitsu.com>
To: Dave Young <dyoung@redhat.com>
Cc: Junichi Nomura <j-nomura@ce.jp.nec.com>,
	Borislav Petkov <bp@alien8.de>, "bhe@redhat.com" <bhe@redhat.com>,
	"kasong@redhat.com" <kasong@redhat.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel
Date: Wed, 3 Apr 2019 13:35:00 +0800	[thread overview]
Message-ID: <20190403053459.GD1555@localhost.localdomain> (raw)
In-Reply-To: <20190402120319.GA7605@dhcp-128-65.nay.redhat.com>

On Tue, Apr 02, 2019 at 08:03:19PM +0800, Dave Young wrote:
>On 04/01/19 at 12:08am, Junichi Nomura wrote:
>> Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
>> boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
>> in the early parsing code tries to search RSDP from EFI table but
>> that will crash because the table address is virtual when the kernel
>> was booted by kexec.
>> 
>> In the case of kexec, physical address of EFI tables is provided
>> via efi_setup_data in boot_params, which is set up by kexec(1).
>> 
>> Factor out the table parsing code and use different pointers depending
>> on whether the kernel is booted by kexec or not.
>> 
>> Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
>> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
>> Acked-by: Baoquan He <bhe@redhat.com>
>> Cc: Chao Fan <fanc.fnst@cn.fujitsu.com>
>> Cc: Borislav Petkov <bp@suse.de>
>> Cc: Dave Young <dyoung@redhat.com>
[...]
>
>I failed to kexec reboot on my laptop, kernel panics too quick,  I'm not sure this is
>caused by your patch though.
>
>Actually there are something probably i915 changes break kexec,  the
>above test is with "nomodeset" which should work.
>
>Let me do more testing and update here tomorrow.
>

Hi Dave,

Last day I was testing the normal kexec, today I have tested the kdump
issue. Since the kdump has set "nokaslr" to cmdline, so I drop from
KDUMP_COMMANDLINE_APPEND
And it booted OK, so the PATCH works in both normal kexec and kdump.

[root@localhost ~]# echo 1 > /proc/sys/kernel/sysrq
[root@localhost ~]# echo c > /proc/sysrq-trigger
[   67.776136] sysrq: Trigger a crash
[   67.777412] Kernel panic - not syncing: sysrq triggered crash
[   67.779429] CPU: 1 PID: 1652 Comm: bash Kdump: loaded Not tainted 5.1.0-rc3+ #4
[   67.780755] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
[   67.782062] Call Trace:
[   67.782490]  dump_stack+0x5c/0x80
[   67.783049]  panic+0x101/0x2a7
[   67.783560]  ? printk+0x58/0x6f
[   67.784091]  sysrq_handle_crash+0x11/0x11
[   67.784762]  __handle_sysrq.cold.7+0x45/0xf2
[   67.785467]  write_sysrq_trigger+0x2b/0x30
[   67.786087]  proc_reg_write+0x39/0x60
[   67.786597]  vfs_write+0xa5/0x1a0
[   67.787061]  ksys_write+0x4f/0xb0
[   67.787492]  do_syscall_64+0x5b/0x160
[   67.788010]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   67.788740] RIP: 0033:0x7f66266fbed8
[   67.789239] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 45 78 0d 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 d4 55
[   67.791325] RSP: 002b:00007ffecdaf6138 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[   67.792084] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f66266fbed8
[   67.792820] RDX: 0000000000000002 RSI: 000055dcc8d29880 RDI: 0000000000000001
[   67.793515] RBP: 000055dcc8d29880 R08: 000000000000000a R09: 00007ffecdaf5cc0
[   67.794276] R10: 000000000000000a R11: 0000000000000246 R12: 00007f66267cf780
[   67.795017] R13: 0000000000000002 R14: 00007f66267ca740 R15: 0000000000000002
early console in extract_kernel
input_data: 0x00000000376033b1
input_len: 0x00000000008412d4
output: 0x0000000036000000
output_len: 0x0000000001e15844
kernel_total_size: 0x0000000001e2c000
trampoline_32bit: 0x000000000009d000
booted via startup_64()

Physical KASLR disabled: no suitable memory region!

Virtual KASLR using RDRAND RDTSC...

Decompressing Linux... Parsing ELF... Performing relocations... done.
Booting the kernel.
[...]
         Starting Kdump Vmcore Save Service...
kdump: dump target is /dev/mapper/fedora-root
kdump: saving to /sysroot//var/crash/127.0.0.1-2019-04-03-01:28:01/
[    3.551609] EXT4-fs (dm-0): re-mounted. Opts: (null)
kdump: saving vmcore-dmesg.txt
kdump: saving vmcore-dmesg.txt complete
kdump: saving vmcore
Copying data                                      : [100.0 %] |           eta: 0s
kdump: saving vmcore complete

Thanks,
Chao Fan

>Thanks
>Dave
>
>
>