Re: [edk2] KVM: MTRR: fix memory type handling if MTRR is completely disabled

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

Thanks for your report and analysis, Janusz!

On 09/19/2015 01:48 AM, Janusz wrote:
> W dniu 18.09.2015 o 12:07, Laszlo Ersek pisze:
>> On 09/18/15 11:37, Janusz wrote:
>>> Hello,
>>>
>>> I am writting about this patch that was posted by Xiao:
>>> http://www.spinics.net/lists/kvm/msg119044.html and this:
>>> http://www.spinics.net/lists/kvm/msg119045.html
>>> I've tested both kernel 4.2 and 4.3 and problem still exists when I use
>>> OVMF - 100% cpu usage, VM resetting, while it works properly on kernel 4.1
>> My last (still current) request remains "please quirk it". See the end
>> of <http://thread.gmane.org/gmane.linux.kernel/1952205/focus=1996025>,
>> and other messages in that subthread.
> when I saw message from Xiao that he posted patch for it and have seen
> this code in kernel sources (landed in 4.2-rc3) I though that the status
> is not "please quirk it" anymore
>>
>> I haven't been following kernel development, so maybe the quirk has not
>> happened. No clue.
>>
>> ... "VM resetting" looks something different though; I've been under the
>> impression that the pedantic (=unquirked) MTRR configuration didn't
>> impact other things than speed. Janusz, maybe you could contribute with
>> a host kernel bisection for the VM reset symptom.
> To be more exact - VM is mostly not starting or its starting after long
> time and then resetting it self at random time (but before system boots)
> or gets very high cpu usage or sometimes boots without problem (the
> least possible case scenario). When I start VM with -vga std, not with
> my gpu passthrough - in most of the time I get this:
> http://pastebin.com/raw.php?i=CKrNsueS

It seems the behaviour is different with previous (previously, it can boot
but slowly), right?

The URL cat not be accessed, i do not know it's your web server issue or
our networking issue.

>
> Result of bisect:
>
> git bisect start
> # bad: [d770e558e21961ad6cfdf0ff7df0eb5d7d4f0754] Linux 4.2-rc1
> git bisect bad d770e558e21961ad6cfdf0ff7df0eb5d7d4f0754
> # good: [b953c0d234bc72e8489d3bf51a276c5c4ec85345] Linux 4.1
> git bisect good b953c0d234bc72e8489d3bf51a276c5c4ec85345
> # good: [4570a37169d4b44d316f40b2ccc681dc93fedc7b] Merge tag
> 'sound-4.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
> git bisect good 4570a37169d4b44d316f40b2ccc681dc93fedc7b
> # good: [8d7804a2f03dbd34940fcb426450c730adf29dae] Merge tag
> 'driver-core-4.2-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
> git bisect good 8d7804a2f03dbd34940fcb426450c730adf29dae
> # bad: [78c10e556ed904d5bfbd71e9cadd8ce8f25d6982] Merge branch
> 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus
> git bisect bad 78c10e556ed904d5bfbd71e9cadd8ce8f25d6982
> # good: [623f0e137c0fedb81bbf3d88be4ed300eee163da] Staging: lustre: fix
> space before and after comma in dt_object.c
> git bisect good 623f0e137c0fedb81bbf3d88be4ed300eee163da
> # bad: [8c7febe83915332276cab49e89f6580bb963fb9a] Merge tag
> 'tty-4.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
> git bisect bad 8c7febe83915332276cab49e89f6580bb963fb9a
> # good: [bcf5b92d9bbf0b7683199615f0f184e89fa486bc] staging: rtl8192e:
> Remove rt_hi_throughput::ChnkOp
> git bisect good bcf5b92d9bbf0b7683199615f0f184e89fa486bc
> # good: [71eec4836b834b992e0cefeefc8b85efe4cb185b] drivers: PL011: allow
> avoiding UART enabling/disabling
> git bisect good 71eec4836b834b992e0cefeefc8b85efe4cb185b
> # good: [49ef9c850154756cf2fbc50fd3804c44675d4633] staging: comedi:
> me4000: rename 'thisboard' variables
> git bisect good 49ef9c850154756cf2fbc50fd3804c44675d4633
> # good: [2a4462418af771ef9f1f1d1532bcbb8799df842d] tty/serial: kill off
> set_irq_flags usage
> git bisect good 2a4462418af771ef9f1f1d1532bcbb8799df842d
> # good: [6d43b0f482561ab421a91ebf59a51192d66cf8a7] Staging: sm750fb:
> ddk750_swi2c.c: Insert spaces around operators
> git bisect good 6d43b0f482561ab421a91ebf59a51192d66cf8a7
> # good: [84e1eb83d0b9e0969a59b6848d718eaf71e98fcb] MAINTAINERS: tty: add
> serial docs directory
> git bisect good 84e1eb83d0b9e0969a59b6848d718eaf71e98fcb
> # good: [53a20e9e378ecd52f0afa4b60f8f8c81b6f97c27] staging: wilc1000:
> disable driver due to build warnings
> git bisect good 53a20e9e378ecd52f0afa4b60f8f8c81b6f97c27
> # good: [71206b9f8120eb513c621d4f31906577bb658df3] Doc:
> serial-rs485.txt: update RS485 driver interface
> git bisect good 71206b9f8120eb513c621d4f31906577bb658df3
> # bad: [23908db413eccd77084b09c9b0a4451dfb0524c0] Merge tag
> 'staging-4.2-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
> git bisect bad 23908db413eccd77084b09c9b0a4451dfb0524c0
> # first bad commit: [23908db413eccd77084b09c9b0a4451dfb0524c0] Merge tag
> 'staging-4.2-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
>

The bad commit is:
commit 23908db413eccd77084b09c9b0a4451dfb0524c0
Merge: 8d7804a 53a20e9
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri Jun 26 15:46:08 2015 -0700

Hard to find which one causes the real issue... but i will try to reproduce
it, could you please share your command line?