2016-06-21 21:59 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>: > Hi Paolo, > 2016-06-21 18:24 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>: >> 2016-06-21 18:10 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: >>> >>> >>> On 21/06/2016 08:08, Wanpeng Li wrote: >>>> Cc KVM ML, Paolo, Radim, >>>>>> FYI, raw QEMU command line is: >>>>>> >>>>>> qemu-system-x86_64 -enable-kvm -cpu SandyBridge -kernel /pkg/linux/x86_64-randconfig-w0-06180628/gcc-6/19fa5e73647fde1e6a7038a8f05cddf4c43f08d3/vmlinuz-4.7.0-rc3-00009-g19fa5e7 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-yocto-x86_64-32/bisect_boot-1-yocto-minimal-x86_64.cgz-x86_64-randconfig-w0-06180628-19fa5e73647fde1e6a7038a8f05cddf4c43f08d3-20160618-25535-h82bax-0.yaml~ ARCH=x86_64 kconfig=x86_64-randconfig-w0-06180628 branch=internal-eywa/master commit=19fa5e73647fde1e6a7038a8f05cddf4c43f08d3 BOOT_IMAGE=/pkg/linux/x86_64-randconfig-w0-06180628/gcc-6/19fa5e73647fde1e6a7038a8f05cddf4c43f08d3/vmlinuz-4.7.0-rc3-00009-g19fa5e7 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-kbuild-yocto-x86_64/yocto-minimal-x86_64.cgz/x86_64-randconfig-w0-06180628/gcc-6/19fa5e73647fde1e6a7038a8f05cddf4c43f08d3/0 LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw ip=::::vm-kbuild-yocto-x86_64-32::dhcp drbd.minor_count=8' -initrd /fs/sdh1/initrd-vm-kbuild-yocto-x86_64-32 -m 320 -smp 1 -device e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive file=/fs/sdh1/disk0-vm-kbuild-yocto-x86_64-32,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-kbuild-yocto-x86_64-32 -serial file:/dev/shm/kboot/serial-vm-kbuild-yocto-x86_64-32 -daemonize -display none -monitor null >>>>>> >>>>> This problem was caused due to kvm does not support MSR_PLATFORM_INFO(0xce), >>>>> according to Wanpeng's feedback. >>>>> >>>>> Hi Wanpeng, is it possible for kvm to simulate this MSR, otherwise we >>>>> might have to use >>>>> rdmsr_safe instead. >>>> >>>> There is a thread discussed this before >>>> https://patchwork.kernel.org/patch/8833021/, MSR_PLATFORM_INFO can't >>>> be simple emulation. >>>> >>>> Ping Paolo, Radim. :) >>> >>> rdmsr_safe must be used instead. I'll prepare a patch. >> >> Actually I have such a patch on hand under testing, I will send out soon. :) > > I have a temporal patch as below, it seems that guest tsc(~300MHz) is > still not correct and guest kernel panic during boot w/ message > "MP-BIOS bug: 8254 timer not connect to IO-APIC, kernel-panic - not > syncing: IOAPIC + timer doesn't work" etc. Any proposal to improve my > patch is a great appreciated. :) The patch is against x86 branch on > Len Brown's tree. And try to fix this commit: > https://git.kernel.org/cgit/linux/kernel/git/lenb/linux.git/commit/?h=x86&id=fc141535ad8a67fd58623289c04e35465e2a07f2 > > -------------------- > > From 8033ae4c7e44d6bfe26642b151de03c613125066 Mon Sep 17 00:00:00 2001 > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > Date: Tue, 21 Jun 2016 19:41:12 +0800 > Subject: [PATCH] x86: fix rdmsr MSR_PLATFORM_INFO unsafe warning in kvm guest > > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 0 at arch/x86/mm/extable.c:50 > ex_handler_rdmsr_unsafe+0x6a/0x70 > unchecked MSR access error: RDMSR from 0xce > Modules linked in: > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.7.0-rc3+ #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > 0000000000000000 ffffffff81c03ce0 ffffffff813b3eae ffffffff81c03d30 > 0000000000000000 ffffffff81c03d20 ffffffff81067181 0000003200000001 > ffffffff81c03df8 ffffffff8179676c 0000000000000000 ffffffff81fcd2c0 > Call Trace: > dump_stack+0x67/0x99 > __warn+0xd1/0xf0 > warn_slowpath_fmt+0x4f/0x60 > ex_handler_rdmsr_unsafe+0x6a/0x70 > fixup_exception+0x39/0x50 > do_general_protection+0x93/0x1b0 > general_protection+0x22/0x30 > ? cpu_khz_from_msr+0xd8/0x1c0 > native_calibrate_cpu+0x30/0x5b0 > tsc_init+0x2b/0x297 > x86_late_time_init+0xf/0x11 > start_kernel+0x398/0x451 > ? set_init_arg+0x55/0x55 > x86_64_start_reservations+0x2f/0x31 > x86_64_start_kernel+0xea/0xed > > After commit (fc141535ad8 : "x86 tsc_msr: Extend to include Intel Core > Architecture"), > rdmsr MSR_PLATFORM_INFO is used to get maximum non-turbo ratio for > recent Intel Core > Architecture which results in kvm guest rdmsr unsafe warning. > > As Radim pointed out before: > > | MSR_PLATFORM_INFO: Intel changes it from family to family and there is > | no obvious overlap or default. If we picked 0 (any other fixed value), > | then the guest would have to know that 0 doesn't mean that > | MSR_PLATFORM_INFO returned 0, but that KVM doesn't emulate this MSR and > | the value cannot be used. This is very similar to handling a #GP in the > | guest, but also has a disadvantage, because KVM cannot say that > | MSR_PLATFORM_INFO is 0. Simple emulation is not possible. > > This patch fix it by using rdmsr_safe to read MSR_PLATFORM_INFO in kvm guest > in order that #GP can be fixed up. > > Reported-by: kernel test robot <xiaolong.ye@xxxxxxxxx> > Cc: Len Brown <len.brown@xxxxxxxxx> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> > Cc: Zhang Rui <rui.zhang@xxxxxxxxx> > Cc: Chen Yu <y.c.chen@xxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Cc: jacob.jun.pan@xxxxxxxxx > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > --- > arch/x86/kernel/tsc_msr.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c > index e0c2b30..15e06e1 100644 > --- a/arch/x86/kernel/tsc_msr.c > +++ b/arch/x86/kernel/tsc_msr.c > @@ -123,8 +123,11 @@ unsigned long cpu_khz_from_msr(void) > } > > get_ratio: > - rdmsr(MSR_PLATFORM_INFO, lo, hi); > - ratio = (lo >> 8) & 0xff; > + if (rdmsr_safe(MSR_PLATFORM_INFO, &lo, &hi)) { > + rdmsr(MSR_IA32_PERF_STATUS, lo, hi); > + ratio = (hi >> 8) & 0x1f; I think this should fallback to PIT calibration instead of MSR_IA32_PERF_STATUS. In addition, I remember Radim mentioned that "PERF_CTL the target value for PERF_STATUS, but OS shouldn't put much trust in those values ... especially under KVM, where those MSRs make little sense." I will try it today. Regards, Wanpeng Li -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
