| Message ID | tip-37c528ee1af7f24eb31f4195b8b7d4f23e6c716d@git.kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c index e0c2b30..e6e465e 100644 --- a/arch/x86/kernel/tsc_msr.c +++ b/arch/x86/kernel/tsc_msr.c @@ -70,7 +70,7 @@ static int match_cpu(u8 family, u8 model) */ unsigned long cpu_khz_from_msr(void) { - u32 lo, hi, ratio, freq_id, freq; + u32 lo, hi, freq_id, freq, ratio = 0; unsigned long res; int cpu_index; @@ -123,8 +123,8 @@ 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)) + ratio = (lo >> 8) & 0xff; done: /* TSC frequency = maximum resolved freq * maximum resolved bus ratio */
Commit-ID: 37c528ee1af7f24eb31f4195b8b7d4f23e6c716d Gitweb: http://git.kernel.org/tip/37c528ee1af7f24eb31f4195b8b7d4f23e6c716d Author: Wanpeng Li <wanpeng.li@hotmail.com> AuthorDate: Wed, 22 Jun 2016 09:28:28 +0800 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 11 Jul 2016 09:20:36 +0200 x86/tsc_msr: Fix rdmsr(MSR_PLATFORM_INFO) unsafe warning in KVM guest After this commit: fc273eeef314 ("x86/tsc_msr: Extend to include Intel Core Architecture") The following unsafe MSR reading warning triggers: 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 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 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. Fix it by using rdmsr_safe(MSR_PLATFORM_INFO) in KVM guest to not trigger a #GP, then tsc will be calibrated by a fallback method: PIT, HPET etc. Reported-by: kernel test robot <xiaolong.ye@intel.com> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Cc: Chen Yu <y.c.chen@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Len Brown <len.brown@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Linux PM list <linux-pm@vger.kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Zhang Rui <rui.zhang@intel.com> Cc: jacob.jun.pan@intel.com Cc: kvm@vger.kernel.org Cc: linux-acpi@vger.kernel.org Cc: lkp@01.org Link: http://lkml.kernel.org/r/1466558908-3524-1-git-send-email-wanpeng.li@hotmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/kernel/tsc_msr.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html