On 08/13/2013 06:55 PM, Jingbai Ma wrote: > On 08/06/2013 05:19 PM, HATAYAMA Daisuke wrote: >> Hello, >> >> I've addressing kdump restriction that there's only one cpu available >> on the kdump 2nd kernel. Now I need to check if the following CPU0 SMI >> corruption issue fixed in the following commit can again be reproduced >> by unsetting BSP flag of the boot cpu: >> >> commit 74b5820808215f65b70b05a099d6d3c969b82689 >> Author: Bjorn Helgaas<bjorn.helgaas at hp.com> >> Date: Wed Jul 29 15:54:25 2009 -0600 >> >> ACPI: bind workqueues to CPU 0 to avoid SMI corruption >> >> On some machines, a software-initiated SMI causes corruption unless the >> SMI runs on CPU 0. An SMI can be initiated by any AML, but typically it's >> done in GPE-related methods that are run via workqueues, so we can avoid >> the known corruption cases by binding the workqueues to CPU 0. >> >> References: >> http://bugzilla.kernel.org/show_bug.cgi?id=13751 >> https://bugs.launchpad.net/bugs/157171 >> https://bugs.launchpad.net/bugs/157691 >> >> Signed-off-by: Bjorn Helgaas<bjorn.helgaas at hp.com> >> Signed-off-by: Len Brown<len.brown at intel.com> >> >> The reason is that in the current situation, I have two ideas to deal >> with the avove kdump restriction: >> >> 1) Disable BSP at the 2nd kernel, posted at: >> [PATCH v1 0/2] x86, apic: Disable BSP if boot cpu is AP >> https://lkml.org/lkml/2012/10/16/15 >> >> 2) Unset BSP flag at the 1st kernel, suggested by Eric Biederman >> during the discussion of the idea 1). >> >> On the idea 1), BSP is disabled on the kdump 2nd kernel. My conclusion >> is that we have no method to reset BSP, i.e. recover BPS's healthy >> state, while we can recover AP by means of INIT as described in MP >> specification. >> >> The idea 2) is simpler. We unset BSP flag of the boot cpu at 1st >> kernel. The behaviour when receiving INIT depends on whether or not >> BSP flag is set or not on its MSR; we can set and unset BSP flag of >> MSR freely at runtime. (I don't mean we should). >> >> So, next thing I should do is to evalute risk of the idea 2). In fact, >> during the discussion of the idea 1), HPA pointed out that some kind >> of firmware affects if BSP flag is unset. Also, maybe from the same >> reason, recently introduced cpu0 hot-plugging feature by Fenghua Yu >> doesn't appear to unset BSP flag. >> >> The biggest problem next is that I don't have any machines reported in >> the bugzilla articles; this issue inherently depends on firmware. >> >> So, could anyone help testing the idea 2) above if you have which of >> the following machines? (or other ones that can lead to the same bug) >> >> - HP Compaq 6910p >> - HP Compaq 6710b >> - HP Compaq 6710s >> - HP Compaq 6510b >> - HP Compaq 2510p >> >> I prepared a small programs for this test. See the attached file. >> The steps to try to reproduce the bug is as follows: >> >> 1. $ tar xf bsp_flag_modules.tar.gz; cd bsp_flag_modules >> 2. $ make # to build these programs >> 3. $ insmod unsetbspflag.ko # to unset BSP flag of the boot cpu >> 4. $ insmod getcpuinfo.ko # to confirm if BSP flag of the boot cpu has >> # been unset. >> $ dmesg | tail >> 5. Close the lid of the machine. >> 6. Wait some minutes if necessary. >> 7. Open the lid and you can see oops on the screen if bug has >> successfully been reproduced. >> > > I couldn't find any model list above, but found one HP EliteBook 6930p. > I tested this machine with kernel 2.6.30 first. After resuming from > suspend, system hang. > > Then, I tested with kernel 3.11.0-rc5, it worked well, could resume from > suspend without any problem. > > Next, I tested your program to clear BSP flag, I found the > unsetbspflag.ko didn't work everytime, sometimes I have to execute > insmod/rmmod several times to clear the BSP flag. (I used your > getcpuinfo.ko to check the BSP flag) > > cpu: 0 bios_apic: 0 apic: 0 AP > cpu: 1 bios_apic: 1 apic: 1 AP > > I suspended it, and them resumed it. This machine resumed from suspend > successfully, but the BSP flag has been set back: > > cpu: 0 bios_apic: 0 apic: 0 BSP > cpu: 1 bios_apic: 1 apic: 1 AP > > That's all my observation. Hope it's helpful. > I found a side effect of unsetting BSP flag. It affected system rebooting, once the BSP flags been removed, and issue reboot command, system will hang after message: Restarting system. And have to do a hardware reset to recover it. I have reproduced this problem on the following systems: HP EliteBook 6930p HP Compaq DC7700 HP ProLiant DL980 (4 sockets, 40 cores) I have an idea: To avoid such kind of issue, we can unset BSP flag in the first kernel during crash processing, and restore it in the second kernel in the APs initializing. -- Thanks, Jingbai Ma
