Re: [edk2] KVM: MTRR: fix memory type handling if MTRR is completely disabled

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 10/15/2015 02:19 PM, Janusz wrote:
> W dniu 15.10.2015 o 06:19, Xiao Guangrong pisze:
>>
>>
>>
>> Well, the bug may be not in KVM. When this bug happened, i saw OVMF
>> only checked 1 CPU out, there is the log from OVMF's debug input:
>>
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCD
>>    Flushing GCDs
>> Detect CPU count: 1
>>
>> So that the startup code has been freed however the APs are still
>> running,
>> i think that why we saw the vCPUs executed on unexpected address.
>>
>> After digging into OVMF's code, i noticed that BSP CPU waits for APs
>> for a fixed timer period, however, KVM recent changes require zap all
>> mappings if CR0.CD is changed, that means the APs need more time to
>> startup.
>>
>> After following changes to OVMF, the bug is completely gone on my side:
>>
>> --- a/UefiCpuPkg/CpuDxe/ApStartup.c
>> +++ b/UefiCpuPkg/CpuDxe/ApStartup.c
>> @@ -454,7 +454,9 @@ StartApsStackless (
>>     //
>>     // Wait 100 milliseconds for APs to arrive at the ApEntryPoint routine
>>     //
>> -  MicroSecondDelay (100 * 1000);
>> +  MicroSecondDelay (10 * 100 * 1000);
>>
>>     return EFI_SUCCESS;
>>   }
>>
>> Janusz, could you please check this instead? You can switch to your
>> previous kernel to do this test.
>>
>>
> Ok, now first time when I started VM I was able to start system
> successfully. When I turned it off and started it again, it restarted my
> vm at system boot couple of times. Sometimes I also get very high cpu
> usage for no reason. Also, I get less fps in GTA 5 than in kernel 4.1, I
> get something like 30-55, but on 4.1 I get all the time 60 fps. This is
> my new log: https://bpaste.net/show/61a122ad7fe5
>

Just confirm: the Qemu internal error did not appear any more, right?