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; + } else + ratio = (lo >> 8) & 0xff; done: /* TSC frequency = maximum resolved freq * maximum resolved bus ratio */ -- 1.9.1 -- 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
