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. -- Thanks, Jingbai Ma
