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Date:      Tue, 13 Sep 2016 17:54:26 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        Slawa Olhovchenkov <slw@zxy.spb.ru>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, stable@FreeBSD.org
Subject:   Re: X2APIC support
Message-ID:  <37f5cebc-3fa1-9e95-5123-f3d8daa3130a@FreeBSD.org>
In-Reply-To: <20160913142118.GA34394@zxy.spb.ru>
References:  <20160912093905.GP34394@zxy.spb.ru> <cfc61757-482a-ee21-e1a1-84d68bc39c00@FreeBSD.org> <20160912164412.GS34394@zxy.spb.ru> <5662c700-f139-4754-8693-7adc0f2657be@FreeBSD.org> <20160912175348.GV34394@zxy.spb.ru> <b03e7fa0-b73f-de92-b783-de8be2d66107@FreeBSD.org> <20160913121133.GX34394@zxy.spb.ru> <71a1f864-66de-0010-5024-e8e985f422f4@FreeBSD.org> <20160913124239.GZ34394@zxy.spb.ru> <c6e1a647-344b-a6d7-9f48-65092533ed21@FreeBSD.org> <20160913142118.GA34394@zxy.spb.ru>

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On 13/09/2016 17:21, Slawa Olhovchenkov wrote:
> boot failed:
> 
> set hw.x2apic_enable=0
> loading required module 'krpc'
> /boot/kernel.VSTREAM/krpc.ko size 0x2a210 at 0x134e000
> loading required module 'opensolaris'
>  ^@/boot/kernel.VSTREAM/opensolaris.ko size 0xadb8 at 0x1379000
> /boot/kernel.VSTREAM/if_igb.ko size 0x69f10 at 0x1384000
> can't find 'if_ixgbe'
> /boot/kernel.VSTREAM/if_lagg.ko size 0x150c0 at 0x13ee000^M ^@
> +/boot/kernel.VSTREAM/ukbd.ko size 0xe128 at 0x1404000
> loading required module 'usb'
> /boot/kernel.VSTREAM/usb.ko size 0x458b0 at 0x1413000^M|
>                                                              /boot/kernel.VSTREAM/umass.ko size 0xaa10 at 0x1459000
> /boot/kernel.VSTREAM/accf_http.ko size 0x2710 at 0x1464000
> /boot/kernel.VSTREAM/uhci.ko size 0xd508 at 0x1467000
> /boot/kernel.VSTREAM/ohci.ko size 0xc9d0 at 0x1475000^M                
> /boot/kernel.VSTREAM/ehci.ko size 0xfc40 at 0x1482000
> /boot/kernel.VSTREAM/xhci.ko size 0x11068 at 0x1492000
> /boot/kernel.VSTREAM/cc_htcp.ko size 0x3a70 at 0x14a4000
> Booting...
> Copyright (c) 1992-2016 The FreeBSD Project.
> Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
>         The Regents of the University of California. All rights reserved.
> FreeBSD is a registered trademark of The FreeBSD Foundation.
> FreeBSD 11.0-RELEASE-p305117 #0: Mon Sep 12 20:38:53 MSK 2016
>     slw@edge21.int.integros.com:/usr/obj/usr/src/sys/VSTREAM amd64
> FreeBSD clang version 3.8.0 (tags/RELEASE_380/final 262564) (based on LLVM 3.8.0)
> VT(vga): text 80x25
> CPU: Intel(R) Xeon(R) CPU E5-2650 v4 @ 2.20GHz (2200.04-MHz K8-class CPU)
>   Origin="GenuineIntel"  Id=0x406f1  Family=0x6  Model=0x4f  Stepping=1
>   Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>   Features2=0x7ffefbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,SDBG,FMA,CX16,xTPR,PDCM,PCID,DCA,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>   AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>   AMD Features2=0x121<LAHF,ABM,Prefetch>
>   Structured Extended Features=0x21cbfbb<FSGSBASE,TSCADJ,BMI1,HLE,AVX2,SMEP,BMI2,ERMS,INVPCID,RTM,PQM,NFPUSG,PQE,RDSEED,ADX,SMAP,PROCTRACE>
>   XSAVE Features=0x1<XSAVEOPT>
>   VT-x: PAT,HLT,MTF,PAUSE,EPT,UG,VPID,VID,PostIntr
>   TSC: P-state invariant, performance statistics
> real memory  = 137438953472 (131072 MB)
> avail memory = 133407973376 (127227 MB)
> Event timer "LAPIC" quality 600
> ACPI APIC Table: <ALASKA A M I >
> boot_cpu_id = 255
> kernel trap 12 with interrupts disabled
> 
> 
> Fatal trap 12: page fault while in kernel mode
> cpuid = 0; apic id = ff
> fault virtual address   = 0x0
> fault code              = supervisor read data, page not present
> instruction pointer     = 0x20:0xffffffff80537e74
> stack pointer           = 0x28:0xffffffff814b3a60
> frame pointer           = 0x28:0xffffffff814b3a70
> code segment            = base 0x0, limit 0xfffff, type 0x1b
>                         = DPL 0, pres 1, long 1, def32 0, gran 1
> processor eflags        = resume, IOPL = 0
> current process         = 0 ()
> trap number             = 12
> panic: page fault
> cpuid = 0
> KDB: stack backtrace:
> #0 0xffffffff805272e7 at kdb_backtrace+0x67
> #1 0xffffffff804dd662 at vpanic+0x182
> #2 0xffffffff804dd4d3 at panic+0x43
> #3 0xffffffff807a37a1 at trap_fatal+0x351
> #4 0xffffffff807a3993 at trap_pfault+0x1e3
> #5 0xffffffff807a2f1c at trap+0x26c
> #6 0xffffffff80787ca1 at calltrap+0x8
> #7 0xffffffff8083b53a at topo_probe+0x61a
> #8 0xffffffff8078fe93 at cpu_mp_start+0x1c3
> #9 0xffffffff805382ca at mp_start+0x3a
> #10 0xffffffff80465cd8 at mi_startup+0x118
> #11 0xffffffff8028dfac at btext+0x2c
> Uptime: 1s

Thank you!
It seems like exactly the same behavior that happens when you toggle that BIOS
option.

My theory is that in both cases, hw.x2apic_enable=0 and X2APIC_OPT_OUT is on,
the BIOS turns on x2APIC mode and transitions to OS in that mode.
In the case when X2APIC_OPT_OUT is on it's clearly a BIOS bug.
But maybe we could do a little bit better in both cases.  At the very least we
could detect the situation and panic with a helpful message (e.g. "x2APIC mode
is disabled but turn on by BIOS").  Perhaps we could even try to downgrade to
xAPIC mode.

-- 
Andriy Gapon



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