Hi Nadav,
Thanks for your suggestion, you're right.
I checked my hardwares, the E5620/E5-2620 v3/E5-2690 v4 all support
MONITOR/MWAIT, but my E5-2620 server and E5-2690 server disable MWAIT in the
BIOS, and E5620 server enable. So I made a mistake, sorry guys.
--
Regards,
Longpeng(Mike)
On 2017/6/9 12:51, Nadav Amit wrote:
> Maybe you disabled MWAIT it in the BIOS. Try to read IA32_MISC_ENABLE[18]
> (MSR 0x1a0). If it is clear, MWAIT/MONITOR is disabled.
>
>
>
>
>> On Jun 8, 2017, at 8:52 PM, Longpeng (Mike) <longpeng2@xxxxxxxxxx> wrote:
>>
>>
>> On 2017/6/9 11:47, Longpeng (Mike) wrote:
>>
>>> Hi guys,
>>>
>>> I wrote a testcase which repeat execute MWAIT insn in kvm-unit-test and I tested
>>> it on different hardware, but got different results.
>>>
>>>
>>> 1) cpu: E5620 (hardware don't support MONITOR/MWAIT)
>>>
>>> This works well because I saw the following info in trace:
>>>
>>> CPU 0/KVM-7301 [015] .... 1534719.099573: kvm_exit: reason
>>> MWAIT_INSTRUCTION rip 0x400387 info 0 0
>>> CPU 0/KVM-7301 [015] d... 1534719.099573: kvm_entry: vcpu 0
>>> CPU 0/KVM-7301 [015] .... 1534719.099574: kvm_exit: reason
>>> MWAIT_INSTRUCTION rip 0x400387 info 0 0
>>> CPU 0/KVM-7301 [015] d... 1534719.099574: kvm_entry: vcpu 0
>>>
>>>
>>> 2) cpu: E5-2620 v3 and E5-2690 v4 (both hardwares support MONITOR/MWAIT)
>>>
>>> This...
>>>
>>> CPU 0/KVM-1683 [017] .... 4844125.856164: kvm_exit: reason EXCEPTION_NMI
>>> rip 0x400382 info 0 80000306
>>> CPU 0/KVM-1683 [017] .... 4844125.856166: kvm_emulate_insn: 0:400382:0f
>>> 01 c9 (prot64)
>>> CPU 0/KVM-1683 [017] .... 4844125.856166: kvm_inj_exception: #UD (0x0)
>>> CPU 0/KVM-1683 [017] d... 4844125.856167: kvm_entry: vcpu 0
>>>
>>
>>
>> Sorry, I made a mistake, the trace of result 2 is:
>>
>> CPU 0/KVM-14333 [017] .... 4842658.749717: kvm_exit: reason EXCEPTION_NMI
>> rip 0x400387 info 0 80000306
>> CPU 0/KVM-14333 [017] .... 4842658.749719: kvm_emulate_insn: 0:400387:0f
>> 01 c9 (prot64)
>> CPU 0/KVM-14333 [017] .... 4842658.749719: kvm_inj_exception: #UD (0x0)
>> CPU 0/KVM-14333 [017] d... 4842658.749720: kvm_entry: vcpu 0
>>
>>
>>> and the kvm-unit-test guest reported:
>>>
>>> Unhandled exception 6 #UD at ip 0000000000400387
>>> error_code=0000 rflags=00010002 cs=00000008
>>> rax=0000000000000000 rcx=0000000000000000 rdx=0000000200000000 rbx=0000000000000000
>>> rbp=000000000044db60 rsi=0000000000000001 rdi=0000000000004020
>>> r8=000000000000000a r9=00000000000003f8 r10=000000000044d1e2 r11=000000000044d1e1
>>> r12=0000000000000000 r13=0000000000000000 r14=0000000000000000 r15=0000000000000000
>>> cr0=0000000080010011 cr2=0000000000000000 cr3=0000000007fff000 cr4=0000000000000020
>>> cr8=0000000000000000
>>> STACK: @400387 40028f
>>> 0x0000000000400387: mwait at x86/perf_exit.c:17
>>> /* "mwait %eax, %ecx;" */
>>>> asm volatile(".byte 0x0f, 0x01, 0xc9;"
>>> :: "a" (eax), "c" (ecx));
>>> (inlined by) main at x86/perf_exit.c:93
>>> mb();
>>>> mwait(0, 0);
>>> mb();
>>> 0x000000000040028e: start64 at x86/cstart64.S:206
>>> lea __argv(%rip), %rsi
>>>> call main
>>> mov %eax, %edi
>>>
>>> In result 2, the trace shows that vcpu is in 64bit protect-mode (the testcase
>>> didn't jump to ring3 manually, so it's in ring0), as intel vol2 said the MWAIT
>>> will #UD in this situation when:
>>>
>>> #UD If the current privilege level is not 0.
>>> If CPUID.01H:ECX.MONITOR[bit 3] = 0.
>>>
>>> I think CPUID.01H:ECX.MONITOR does not matter, so I'm so curious about the
>>> result 2 .
>>>
>>> Do you have any idea ? Thanks.
>>>
>>> PS: Wanpeng tested this on his laptop (maybe the cpu is Core-i7) and it worked
>>> well as result 1.
>>>
>>> kvm version : 4.4.11
>>> host kernel : 3.10
>>>
>>>
>>> The testcase is:
>>>
>>> #include "libcflat.h"
>>> #include "smp.h"
>>> #include "vm.h"
>>> #include "processor.h"
>>> #include "desc.h"
>>> #include "apic.h"
>>> #include "apic-defs.h"
>>> #include "asm/barrier.h"
>>>
>>> [...]
>>>
>>> static inline void mwait(unsigned long eax, unsigned long ecx)
>>> {
>>> /* "mwait %eax, %ecx;" */
>>> asm volatile(".byte 0x0f, 0x01, 0xc9;"
>>> :: "a" (eax), "c" (ecx));
>>> }
>>>
>>> [...]
>>>
>>> int main(int argc, char **argv)
>>> {
>>> setup_vm();
>>> smp_init();
>>>
>>> while (test_cnt--) {
>>> [...]
>>> mwait(0, 0);
>>> [...]
>>> }
>>> [...]
>>> }
>>>
>>>
>>
>>
>> --
>> Regards,
>> Longpeng(Mike)
>
>
> .
>
--
Regards,
Longpeng(Mike)
