Messages in this thread | | | Subject | Re: [Xen-devel] PROBLEM: kernel panic xsave_init | From | Boris Ostrovsky <> | Date | Tue, 20 Oct 2015 09:22:16 -0400 |
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On 10/20/2015 08:11 AM, John Doe wrote: > On 20/10/2015 11:51, Jan Beulich wrote: >>>>> On 19.10.15 at 18:25, <boris.ostrovsky@oracle.com> wrote: >>> On 10/19/2015 06:16 AM, John Doe wrote: >>>>>> [ 0.000000] general protection fault: 0000 [#1] SMP >>>>>> [ 0.000000] Modules linked in: >>>>>> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted >>> 4.1.9-6.pvops.qubes.x86_64 #1 >>>>>> [ 0.000000] Hardware name: To Be Filled By O.E.M. To Be Filled By >>> O.E.M./Z170 Extreme4, BIOS P1.80 09/18/2015 >>>>>> [ 0.000000] task: ffffffff81c154c0 ti: ffffffff81c00000 task.ti: >>> ffffffff81c00000 >>>>>> [ 0.000000] RIP: e030:[<ffffffff81d58fad>] [<ffffffff81d58fad>] >>> xstate_enable_boot_cpu+0xde/0x288 >>>>>> [ 0.000000] RSP: e02b:ffffffff81c03de8 EFLAGS: 00010046 >>>>>> [ 0.000000] RAX: 000000000000001f RBX: 0000000000000008 RCX: >>> 0000000000000000 >>>>>> [ 0.000000] RDX: 0000000000000000 RSI: 000000000000001f RDI: >>> 0000000000042660 >>> >>> >>> It would be good to see what's at ffffffff81d58fad. My guess would be >>> that it's xsetbv. >>> >>> If it is then you probably want to make sure you are running hypervisor >>> that has commit e8121c54 ("x86/xsave: enable support for new ISA >>> extensions"). Looks like the first version that has it is 4.5 and you >>> seem to be running 4.4.2. >>> >>> Copying Jan to see if there are plans to backport this (probably not >>> since it's a new feature). >> >> Hmm, if there are features getting exposed that lead to crashes like >> this, then while we wouldn't normally backport enhancements, we >> may need to consider adding a one-off patch to hide respective >> features to that stable branch. But first we of course need to >> understand what is going on here.
The reason I think its this commit is that RAX, RDX and RCX look very much like arguments to xsetbv (which xstate_enable_boot_cpu() executes) and RAX value is 0x1f, which has two new bits that this commit defined.
With this being a new processor (Skylake) it would be logical to have these bits provided by CPUID.
>> >> Jan >> > > I will try with 4.6.0 asap, unfortunately the 4.4.2 image i have is not > built with debug enabled and i'm unable to run gdb at boot, i'm building > a new one right now.
You should be able to use 'gdb /proc/kcore' and look at the instruction at (and around) 0xffffffff81d58fad.
> If you need anything else please be very step-specific since i'm not > very practical at this.
You can also try adding cpuid=['0xd,0:eax=00000000000000000000000000000111'] to your config file and see if it helps.
-boris
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