[PATCH] kvm-pr: manage illegal instructions

[PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

While writing some instruction tests for kvm-unit-tests for powerpc,
I've found that illegal instructions are not managed correctly with kvm-pr,
while it is fine with kvm-hv.

When an illegal instruction (like ".long 0") is processed by kvm-pr,
the kernel logs are filled with:

     Couldn't emulate instruction 0x00000000 (op 0 xop 0)
     kvmppc_handle_exit_pr: emulation at 700 failed (00000000)

While the exception handler receives an interrupt for each instruction
executed after the illegal instruction.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 arch/powerpc/kvm/book3s_emulate.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 2afdb9c..4ee969d 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
 
 	switch (get_op(inst)) {
 	case 0:
-		emulated = EMULATE_FAIL;
 		if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
 		    (inst == swab32(inst_sc))) {
 			/*
@@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
 			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
 			emulated = EMULATE_DONE;
+		} else {
+			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
+			emulated = EMULATE_AGAIN;
 		}
 		break;
 	case 19:
-- 
2.5.0

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

Hi,

as Paolo has merged the test into kvm-unit-tests, this patch (and
original bug) can be now tested with it.

    git://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git

at least:

    be9b007 powerpc: add test to check invalid instruction trap

Run this with KVM-PR and check your dmesg:

qemu-system-ppc64 -machine pseries,accel=kvm \
                  -bios powerpc/boot_rom.bin \
                  -display none -serial stdio \
                  -kernel powerpc/emulator.elf -smp 1

Laurent

On 15/03/2016 21:18, Laurent Vivier wrote:
> While writing some instruction tests for kvm-unit-tests for powerpc,
> I've found that illegal instructions are not managed correctly with kvm-pr,
> while it is fine with kvm-hv.
> 
> When an illegal instruction (like ".long 0") is processed by kvm-pr,
> the kernel logs are filled with:
> 
>      Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>      kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
> 
> While the exception handler receives an interrupt for each instruction
> executed after the illegal instruction.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
> index 2afdb9c..4ee969d 100644
> --- a/arch/powerpc/kvm/book3s_emulate.c
> +++ b/arch/powerpc/kvm/book3s_emulate.c
> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  
>  	switch (get_op(inst)) {
>  	case 0:
> -		emulated = EMULATE_FAIL;
>  		if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>  		    (inst == swab32(inst_sc))) {
>  			/*
> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>  			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>  			emulated = EMULATE_DONE;
> +		} else {
> +			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> +			emulated = EMULATE_AGAIN;
>  		}
>  		break;
>  	case 19:
> 

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

Ping?

On 15/03/2016 21:18, Laurent Vivier wrote:
> While writing some instruction tests for kvm-unit-tests for powerpc,
> I've found that illegal instructions are not managed correctly with kvm-pr,
> while it is fine with kvm-hv.
> 
> When an illegal instruction (like ".long 0") is processed by kvm-pr,
> the kernel logs are filled with:
> 
>      Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>      kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
> 
> While the exception handler receives an interrupt for each instruction
> executed after the illegal instruction.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
> index 2afdb9c..4ee969d 100644
> --- a/arch/powerpc/kvm/book3s_emulate.c
> +++ b/arch/powerpc/kvm/book3s_emulate.c
> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  
>  	switch (get_op(inst)) {
>  	case 0:
> -		emulated = EMULATE_FAIL;
>  		if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>  		    (inst == swab32(inst_sc))) {
>  			/*
> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>  			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>  			emulated = EMULATE_DONE;
> +		} else {
> +			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> +			emulated = EMULATE_AGAIN;
>  		}
>  		break;
>  	case 19:
> 

Re: [PATCH] kvm-pr: manage illegal instructions

[Thomas Huth]

On 15.03.2016 21:18, Laurent Vivier wrote:
> While writing some instruction tests for kvm-unit-tests for powerpc,
> I've found that illegal instructions are not managed correctly with kvm-pr,
> while it is fine with kvm-hv.
> 
> When an illegal instruction (like ".long 0") is processed by kvm-pr,
> the kernel logs are filled with:
> 
>      Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>      kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
> 
> While the exception handler receives an interrupt for each instruction
> executed after the illegal instruction.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
> index 2afdb9c..4ee969d 100644
> --- a/arch/powerpc/kvm/book3s_emulate.c
> +++ b/arch/powerpc/kvm/book3s_emulate.c
> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  
>  	switch (get_op(inst)) {
>  	case 0:
> -		emulated = EMULATE_FAIL;
>  		if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>  		    (inst == swab32(inst_sc))) {
>  			/*
> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>  			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>  			emulated = EMULATE_DONE;
> +		} else {
> +			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> +			emulated = EMULATE_AGAIN;
>  		}
>  		break;
>  	case 19:
> 

Tested-by: Thomas Huth <thuth@redhat.com>

Re: [PATCH] kvm-pr: manage illegal instructions

[Thomas Huth]

On 21.04.2016 11:25, Thomas Huth wrote:
> On 15.03.2016 21:18, Laurent Vivier wrote:
>> While writing some instruction tests for kvm-unit-tests for powerpc,
>> I've found that illegal instructions are not managed correctly with kvm-pr,
>> while it is fine with kvm-hv.
>>
>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>> the kernel logs are filled with:
>>
>>      Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>      kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>
>> While the exception handler receives an interrupt for each instruction
>> executed after the illegal instruction.
>>
>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>> ---
>>  arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
>> index 2afdb9c..4ee969d 100644
>> --- a/arch/powerpc/kvm/book3s_emulate.c
>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>  
>>  	switch (get_op(inst)) {
>>  	case 0:
>> -		emulated = EMULATE_FAIL;
>>  		if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>  		    (inst == swab32(inst_sc))) {
>>  			/*
>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>  			kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>  			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>  			emulated = EMULATE_DONE;
>> +		} else {
>> +			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> +			emulated = EMULATE_AGAIN;
>>  		}
>>  		break;
>>  	case 19:
>>
> 
> Tested-by: Thomas Huth <thuth@redhat.com>

Ping!

Alex, Paul, could you please pick up this patch? This patch is required
to get the kvm-unit-tests working properly with kvm-pr, so I'd be glad
if we could get this included finally...

Thanks,
 Thomas

Re: [PATCH] kvm-pr: manage illegal instructions

[Paolo Bonzini]

On 09/05/2016 10:14, Thomas Huth wrote:
>> > Tested-by: Thomas Huth <thuth@redhat.com>
> Ping!
> 
> Alex, Paul, could you please pick up this patch? This patch is required
> to get the kvm-unit-tests working properly with kvm-pr, so I'd be glad
> if we could get this included finally...

I have a pull request for 4.6 final to send tomorrow; do you want me to
include it?

Thanks,

Paolo

Re: [PATCH] kvm-pr: manage illegal instructions

[Alexander Graf]

On 03/15/2016 09:18 PM, Laurent Vivier wrote:
> While writing some instruction tests for kvm-unit-tests for powerpc,
> I've found that illegal instructions are not managed correctly with kvm-pr,
> while it is fine with kvm-hv.
>
> When an illegal instruction (like ".long 0") is processed by kvm-pr,
> the kernel logs are filled with:
>
>       Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>       kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>
> While the exception handler receives an interrupt for each instruction
> executed after the illegal instruction.
>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>   arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
> index 2afdb9c..4ee969d 100644
> --- a/arch/powerpc/kvm/book3s_emulate.c
> +++ b/arch/powerpc/kvm/book3s_emulate.c
> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>   
>   	switch (get_op(inst)) {
>   	case 0:
> -		emulated = EMULATE_FAIL;
>   		if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>   		    (inst == swab32(inst_sc))) {
>   			/*
> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>   			kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>   			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>   			emulated = EMULATE_DONE;
> +		} else {
> +			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);

But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it 
up in book3s_emulate.c is definitely the wrong spot.

So what is the problem you're trying to solve? Is the SRR0 at the wrong 
spot or are the log messages the problem?


Alex

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

On 11/05/2016 12:35, Alexander Graf wrote:
> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>> While writing some instruction tests for kvm-unit-tests for powerpc,
>> I've found that illegal instructions are not managed correctly with
>> kvm-pr,
>> while it is fine with kvm-hv.
>>
>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>> the kernel logs are filled with:
>>
>>       Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>       kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>
>> While the exception handler receives an interrupt for each instruction
>> executed after the illegal instruction.
>>
>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>> ---
>>   arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>> b/arch/powerpc/kvm/book3s_emulate.c
>> index 2afdb9c..4ee969d 100644
>> --- a/arch/powerpc/kvm/book3s_emulate.c
>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>> struct kvm_vcpu *vcpu,
>>         switch (get_op(inst)) {
>>       case 0:
>> -        emulated = EMULATE_FAIL;
>>           if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>               (inst == swab32(inst_sc))) {
>>               /*
>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>> struct kvm_vcpu *vcpu,
>>               kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>               kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>               emulated = EMULATE_DONE;
>> +        } else {
>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> 
> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
> up in book3s_emulate.c is definitely the wrong spot.
> 
> So what is the problem you're trying to solve? Is the SRR0 at the wrong
> spot or are the log messages the problem?

No, the problem is the host kernel logs are filled by the message and
the execution hangs. And the host becomes unresponsiveness, even after
the end of the tests.

Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
and check the kernel logs (dmesg), then try to ssh to the host...

Laurent

Re: [PATCH] kvm-pr: manage illegal instructions

[Alexander Graf]

On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>
> On 11/05/2016 12:35, Alexander Graf wrote:
>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>> While writing some instruction tests for kvm-unit-tests for powerpc,
>>> I've found that illegal instructions are not managed correctly with
>>> kvm-pr,
>>> while it is fine with kvm-hv.
>>>
>>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>>> the kernel logs are filled with:
>>>
>>>        Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>        kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>
>>> While the exception handler receives an interrupt for each instruction
>>> executed after the illegal instruction.
>>>
>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>> ---
>>>    arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>> b/arch/powerpc/kvm/book3s_emulate.c
>>> index 2afdb9c..4ee969d 100644
>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>> struct kvm_vcpu *vcpu,
>>>          switch (get_op(inst)) {
>>>        case 0:
>>> -        emulated = EMULATE_FAIL;
>>>            if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>                (inst == swab32(inst_sc))) {
>>>                /*
>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>> struct kvm_vcpu *vcpu,
>>>                kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>                kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>                emulated = EMULATE_DONE;
>>> +        } else {
>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
>> up in book3s_emulate.c is definitely the wrong spot.
>>
>> So what is the problem you're trying to solve? Is the SRR0 at the wrong
>> spot or are the log messages the problem?
> No, the problem is the host kernel logs are filled by the message and
> the execution hangs. And the host becomes unresponsiveness, even after
> the end of the tests.
>
> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
> and check the kernel logs (dmesg), then try to ssh to the host...

Ok, so the log messages are the problem. Please fix the message output 
then - or remove it altogether. Or if you like, create a module 
parameter that allows you to emit them.

I personally think the best solution would be to just convert the 
message into a trace point.

While at it, please see whether the guest can trigger similar host log 
output excess in other code paths.


Alex

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

On 11/05/2016 13:49, Alexander Graf wrote:
> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>
>> On 11/05/2016 12:35, Alexander Graf wrote:
>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>> While writing some instruction tests for kvm-unit-tests for powerpc,
>>>> I've found that illegal instructions are not managed correctly with
>>>> kvm-pr,
>>>> while it is fine with kvm-hv.
>>>>
>>>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>>>> the kernel logs are filled with:
>>>>
>>>>        Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>        kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>
>>>> While the exception handler receives an interrupt for each instruction
>>>> executed after the illegal instruction.
>>>>
>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>> ---
>>>>    arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>> index 2afdb9c..4ee969d 100644
>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>> struct kvm_vcpu *vcpu,
>>>>          switch (get_op(inst)) {
>>>>        case 0:
>>>> -        emulated = EMULATE_FAIL;
>>>>            if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>                (inst == swab32(inst_sc))) {
>>>>                /*
>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>> struct kvm_vcpu *vcpu,
>>>>                kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>                kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>                emulated = EMULATE_DONE;
>>>> +        } else {
>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
>>> up in book3s_emulate.c is definitely the wrong spot.
>>>
>>> So what is the problem you're trying to solve? Is the SRR0 at the wrong
>>> spot or are the log messages the problem?
>> No, the problem is the host kernel logs are filled by the message and
>> the execution hangs. And the host becomes unresponsiveness, even after
>> the end of the tests.
>>
>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
>> and check the kernel logs (dmesg), then try to ssh to the host...
> 
> Ok, so the log messages are the problem. Please fix the message output
> then - or remove it altogether. Or if you like, create a module
> parameter that allows you to emit them.
> 
> I personally think the best solution would be to just convert the
> message into a trace point.
> 
> While at it, please see whether the guest can trigger similar host log
> output excess in other code paths.

The problem is not really with the log messages: they are consequence of
the bug I try to fix.

What happens is once kvm_pr decodes an invalid instruction all the valid
following instructions trigger a Program exception to the guest (but are
executed correctly). It has no real consequence on big machine like
POWER8, except that the guest become very slow and the log files of the
host are filled with messages (and qemu uses 100% of the CPU). On a
smaller machine like a  PowerMac G5, the machine becomes simply unusable.

Please try kvm-unit-tests to see what happens:

qemu-system-ppc64 -machine pseries,accel=kvm,kvm-type=PR -bios
powerpc/boot_rom.bin -display none -serial stdio -kernel
powerpc/emulator.elf -smp 1 --append "-v"


Thanks,
Laurent

Re: [PATCH] kvm-pr: manage illegal instructions

[Alexander Graf]

On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>
> On 11/05/2016 13:49, Alexander Graf wrote:
>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>> While writing some instruction tests for kvm-unit-tests for powerpc,
>>>>> I've found that illegal instructions are not managed correctly with
>>>>> kvm-pr,
>>>>> while it is fine with kvm-hv.
>>>>>
>>>>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>>>>> the kernel logs are filled with:
>>>>>
>>>>>         Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>         kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>
>>>>> While the exception handler receives an interrupt for each instruction
>>>>> executed after the illegal instruction.
>>>>>
>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>> ---
>>>>>     arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>     1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>> index 2afdb9c..4ee969d 100644
>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>>> struct kvm_vcpu *vcpu,
>>>>>           switch (get_op(inst)) {
>>>>>         case 0:
>>>>> -        emulated = EMULATE_FAIL;
>>>>>             if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>                 (inst == swab32(inst_sc))) {
>>>>>                 /*
>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>>> struct kvm_vcpu *vcpu,
>>>>>                 kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>                 kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>                 emulated = EMULATE_DONE;
>>>>> +        } else {
>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>
>>>> So what is the problem you're trying to solve? Is the SRR0 at the wrong
>>>> spot or are the log messages the problem?
>>> No, the problem is the host kernel logs are filled by the message and
>>> the execution hangs. And the host becomes unresponsiveness, even after
>>> the end of the tests.
>>>
>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
>>> and check the kernel logs (dmesg), then try to ssh to the host...
>> Ok, so the log messages are the problem. Please fix the message output
>> then - or remove it altogether. Or if you like, create a module
>> parameter that allows you to emit them.
>>
>> I personally think the best solution would be to just convert the
>> message into a trace point.
>>
>> While at it, please see whether the guest can trigger similar host log
>> output excess in other code paths.
> The problem is not really with the log messages: they are consequence of
> the bug I try to fix.
>
> What happens is once kvm_pr decodes an invalid instruction all the valid
> following instructions trigger a Program exception to the guest (but are
> executed correctly). It has no real consequence on big machine like
> POWER8, except that the guest become very slow and the log files of the
> host are filled with messages (and qemu uses 100% of the CPU). On a
> smaller machine like a  PowerMac G5, the machine becomes simply unusable.

It's probably more related to your verbosity level of kernel messages. 
If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get 
the messages printed to serial which is what's slowing you down.

The other problem sounds pretty severe, but the only thing your patch 
does any different from the current code flow would be the patch below. 
Or did I miss anything?

diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index 5cc2e7a..4672bc2 100644
--- a/arch/powerpc/kvm/emulate.c
+++ b/arch/powerpc/kvm/emulate.c
@@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run *run, 
struct kvm_vcpu *vcpu)
                         advance = 0;
                         printk(KERN_ERR "Couldn't emulate instruction 
0x%08x "
                                "(op %d xop %d)\n", inst, get_op(inst), 
get_xop(inst));
+#ifdef CONFIG_PPC_BOOK3S
+                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
+#else
                         kvmppc_core_queue_program(vcpu, 0);
+#endif
                 }
         }

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

On 12/05/2016 11:27, Alexander Graf wrote:
> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>
>> On 11/05/2016 13:49, Alexander Graf wrote:
>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>> While writing some instruction tests for kvm-unit-tests for powerpc,
>>>>>> I've found that illegal instructions are not managed correctly with
>>>>>> kvm-pr,
>>>>>> while it is fine with kvm-hv.
>>>>>>
>>>>>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>>>>>> the kernel logs are filled with:
>>>>>>
>>>>>>         Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>         kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>
>>>>>> While the exception handler receives an interrupt for each
>>>>>> instruction
>>>>>> executed after the illegal instruction.
>>>>>>
>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>> ---
>>>>>>     arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>     1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>> index 2afdb9c..4ee969d 100644
>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>>>> struct kvm_vcpu *vcpu,
>>>>>>           switch (get_op(inst)) {
>>>>>>         case 0:
>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>             if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>                 (inst == swab32(inst_sc))) {
>>>>>>                 /*
>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>> *run,
>>>>>> struct kvm_vcpu *vcpu,
>>>>>>                 kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>                 kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>                 emulated = EMULATE_DONE;
>>>>>> +        } else {
>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>
>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>> wrong
>>>>> spot or are the log messages the problem?
>>>> No, the problem is the host kernel logs are filled by the message and
>>>> the execution hangs. And the host becomes unresponsiveness, even after
>>>> the end of the tests.
>>>>
>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>> Ok, so the log messages are the problem. Please fix the message output
>>> then - or remove it altogether. Or if you like, create a module
>>> parameter that allows you to emit them.
>>>
>>> I personally think the best solution would be to just convert the
>>> message into a trace point.
>>>
>>> While at it, please see whether the guest can trigger similar host log
>>> output excess in other code paths.
>> The problem is not really with the log messages: they are consequence of
>> the bug I try to fix.
>>
>> What happens is once kvm_pr decodes an invalid instruction all the valid
>> following instructions trigger a Program exception to the guest (but are
>> executed correctly). It has no real consequence on big machine like
>> POWER8, except that the guest become very slow and the log files of the
>> host are filled with messages (and qemu uses 100% of the CPU). On a
>> smaller machine like a  PowerMac G5, the machine becomes simply unusable.
> 
> It's probably more related to your verbosity level of kernel messages.
> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
> the messages printed to serial which is what's slowing you down.
> 
> The other problem sounds pretty severe, but the only thing your patch
> does any different from the current code flow would be the patch below.
> Or did I miss anything?
> 
> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
> index 5cc2e7a..4672bc2 100644
> --- a/arch/powerpc/kvm/emulate.c
> +++ b/arch/powerpc/kvm/emulate.c
> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run *run,
> struct kvm_vcpu *vcpu)
>                         advance = 0;
>                         printk(KERN_ERR "Couldn't emulate instruction
> 0x%08x "
>                                "(op %d xop %d)\n", inst, get_op(inst),
> get_xop(inst));
> +#ifdef CONFIG_PPC_BOOK3S
> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> +#else
>                         kvmppc_core_queue_program(vcpu, 0);
> +#endif
>                 }
>         }
> 

OK, that fixes the problem. Thanks. :)

Could you apply it?

Laurent

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

On 12/05/2016 16:23, Laurent Vivier wrote:
> 
> 
> On 12/05/2016 11:27, Alexander Graf wrote:
>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>
>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>> While writing some instruction tests for kvm-unit-tests for powerpc,
>>>>>>> I've found that illegal instructions are not managed correctly with
>>>>>>> kvm-pr,
>>>>>>> while it is fine with kvm-hv.
>>>>>>>
>>>>>>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>>>>>>> the kernel logs are filled with:
>>>>>>>
>>>>>>>         Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>         kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>
>>>>>>> While the exception handler receives an interrupt for each
>>>>>>> instruction
>>>>>>> executed after the illegal instruction.
>>>>>>>
>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>> ---
>>>>>>>     arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>     1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>           switch (get_op(inst)) {
>>>>>>>         case 0:
>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>             if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>                 (inst == swab32(inst_sc))) {
>>>>>>>                 /*
>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>> *run,
>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>                 kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>                 kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>                 emulated = EMULATE_DONE;
>>>>>>> +        } else {
>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>
>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>> wrong
>>>>>> spot or are the log messages the problem?
>>>>> No, the problem is the host kernel logs are filled by the message and
>>>>> the execution hangs. And the host becomes unresponsiveness, even after
>>>>> the end of the tests.
>>>>>
>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>> Ok, so the log messages are the problem. Please fix the message output
>>>> then - or remove it altogether. Or if you like, create a module
>>>> parameter that allows you to emit them.
>>>>
>>>> I personally think the best solution would be to just convert the
>>>> message into a trace point.
>>>>
>>>> While at it, please see whether the guest can trigger similar host log
>>>> output excess in other code paths.
>>> The problem is not really with the log messages: they are consequence of
>>> the bug I try to fix.
>>>
>>> What happens is once kvm_pr decodes an invalid instruction all the valid
>>> following instructions trigger a Program exception to the guest (but are
>>> executed correctly). It has no real consequence on big machine like
>>> POWER8, except that the guest become very slow and the log files of the
>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>> smaller machine like a  PowerMac G5, the machine becomes simply unusable.
>>
>> It's probably more related to your verbosity level of kernel messages.
>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>> the messages printed to serial which is what's slowing you down.
>>
>> The other problem sounds pretty severe, but the only thing your patch
>> does any different from the current code flow would be the patch below.
>> Or did I miss anything?
>>
>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>> index 5cc2e7a..4672bc2 100644
>> --- a/arch/powerpc/kvm/emulate.c
>> +++ b/arch/powerpc/kvm/emulate.c
>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run *run,
>> struct kvm_vcpu *vcpu)
>>                         advance = 0;
>>                         printk(KERN_ERR "Couldn't emulate instruction
>> 0x%08x "
>>                                "(op %d xop %d)\n", inst, get_op(inst),
>> get_xop(inst));
>> +#ifdef CONFIG_PPC_BOOK3S
>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> +#else
>>                         kvmppc_core_queue_program(vcpu, 0);
>> +#endif
>>                 }
>>         }
>>

Do you want I send an updated patch with your changes?

Laurent

Re: [PATCH] kvm-pr: manage illegal instructions

[Alexander Graf]

On 05/17/2016 10:35 AM, Laurent Vivier wrote:
>
> On 12/05/2016 16:23, Laurent Vivier wrote:
>>
>> On 12/05/2016 11:27, Alexander Graf wrote:
>>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>>> While writing some instruction tests for kvm-unit-tests for powerpc,
>>>>>>>> I've found that illegal instructions are not managed correctly with
>>>>>>>> kvm-pr,
>>>>>>>> while it is fine with kvm-hv.
>>>>>>>>
>>>>>>>> When an illegal instruction (like ".long 0") is processed by kvm-pr,
>>>>>>>> the kernel logs are filled with:
>>>>>>>>
>>>>>>>>          Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>>          kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>>
>>>>>>>> While the exception handler receives an interrupt for each
>>>>>>>> instruction
>>>>>>>> executed after the illegal instruction.
>>>>>>>>
>>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>>> ---
>>>>>>>>      arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>>      1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run,
>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>            switch (get_op(inst)) {
>>>>>>>>          case 0:
>>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>>              if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>>                  (inst == swab32(inst_sc))) {
>>>>>>>>                  /*
>>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>> *run,
>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>                  kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>>                  kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>>                  emulated = EMULATE_DONE;
>>>>>>>> +        } else {
>>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it
>>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>>
>>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>>> wrong
>>>>>>> spot or are the log messages the problem?
>>>>>> No, the problem is the host kernel logs are filled by the message and
>>>>>> the execution hangs. And the host becomes unresponsiveness, even after
>>>>>> the end of the tests.
>>>>>>
>>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host,
>>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>>> Ok, so the log messages are the problem. Please fix the message output
>>>>> then - or remove it altogether. Or if you like, create a module
>>>>> parameter that allows you to emit them.
>>>>>
>>>>> I personally think the best solution would be to just convert the
>>>>> message into a trace point.
>>>>>
>>>>> While at it, please see whether the guest can trigger similar host log
>>>>> output excess in other code paths.
>>>> The problem is not really with the log messages: they are consequence of
>>>> the bug I try to fix.
>>>>
>>>> What happens is once kvm_pr decodes an invalid instruction all the valid
>>>> following instructions trigger a Program exception to the guest (but are
>>>> executed correctly). It has no real consequence on big machine like
>>>> POWER8, except that the guest become very slow and the log files of the
>>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>>> smaller machine like a  PowerMac G5, the machine becomes simply unusable.
>>> It's probably more related to your verbosity level of kernel messages.
>>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>>> the messages printed to serial which is what's slowing you down.
>>>
>>> The other problem sounds pretty severe, but the only thing your patch
>>> does any different from the current code flow would be the patch below.
>>> Or did I miss anything?
>>>
>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>> index 5cc2e7a..4672bc2 100644
>>> --- a/arch/powerpc/kvm/emulate.c
>>> +++ b/arch/powerpc/kvm/emulate.c
>>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run *run,
>>> struct kvm_vcpu *vcpu)
>>>                          advance = 0;
>>>                          printk(KERN_ERR "Couldn't emulate instruction
>>> 0x%08x "
>>>                                 "(op %d xop %d)\n", inst, get_op(inst),
>>> get_xop(inst));
>>> +#ifdef CONFIG_PPC_BOOK3S
>>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>> +#else
>>>                          kvmppc_core_queue_program(vcpu, 0);
>>> +#endif
>>>                  }
>>>          }
>>>
> Do you want I send an updated patch with your changes?

Well, you reported the issue and narrowed it down, so feel free to send 
it under your name :). I merely simplified your patch a bit.


Alex

Re: [PATCH] kvm-pr: manage illegal instructions

[Laurent Vivier]

On 17/05/2016 10:37, Alexander Graf wrote:
> On 05/17/2016 10:35 AM, Laurent Vivier wrote:
>>
>> On 12/05/2016 16:23, Laurent Vivier wrote:
>>>
>>> On 12/05/2016 11:27, Alexander Graf wrote:
>>>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>>>> While writing some instruction tests for kvm-unit-tests for
>>>>>>>>> powerpc,
>>>>>>>>> I've found that illegal instructions are not managed correctly
>>>>>>>>> with
>>>>>>>>> kvm-pr,
>>>>>>>>> while it is fine with kvm-hv.
>>>>>>>>>
>>>>>>>>> When an illegal instruction (like ".long 0") is processed by
>>>>>>>>> kvm-pr,
>>>>>>>>> the kernel logs are filled with:
>>>>>>>>>
>>>>>>>>>          Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>>>          kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>>>
>>>>>>>>> While the exception handler receives an interrupt for each
>>>>>>>>> instruction
>>>>>>>>> executed after the illegal instruction.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>>>> ---
>>>>>>>>>      arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>>>      1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>>
>>>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>> *run,
>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>            switch (get_op(inst)) {
>>>>>>>>>          case 0:
>>>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>>>              if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>>>                  (inst == swab32(inst_sc))) {
>>>>>>>>>                  /*
>>>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>> *run,
>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>                  kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>>>                  kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>>>                  emulated = EMULATE_DONE;
>>>>>>>>> +        } else {
>>>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is?
>>>>>>>> Fixing it
>>>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>>>
>>>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>>>> wrong
>>>>>>>> spot or are the log messages the problem?
>>>>>>> No, the problem is the host kernel logs are filled by the message
>>>>>>> and
>>>>>>> the execution hangs. And the host becomes unresponsiveness, even
>>>>>>> after
>>>>>>> the end of the tests.
>>>>>>>
>>>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR
>>>>>>> host,
>>>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>>>> Ok, so the log messages are the problem. Please fix the message
>>>>>> output
>>>>>> then - or remove it altogether. Or if you like, create a module
>>>>>> parameter that allows you to emit them.
>>>>>>
>>>>>> I personally think the best solution would be to just convert the
>>>>>> message into a trace point.
>>>>>>
>>>>>> While at it, please see whether the guest can trigger similar host
>>>>>> log
>>>>>> output excess in other code paths.
>>>>> The problem is not really with the log messages: they are
>>>>> consequence of
>>>>> the bug I try to fix.
>>>>>
>>>>> What happens is once kvm_pr decodes an invalid instruction all the
>>>>> valid
>>>>> following instructions trigger a Program exception to the guest
>>>>> (but are
>>>>> executed correctly). It has no real consequence on big machine like
>>>>> POWER8, except that the guest become very slow and the log files of
>>>>> the
>>>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>>>> smaller machine like a  PowerMac G5, the machine becomes simply
>>>>> unusable.
>>>> It's probably more related to your verbosity level of kernel messages.
>>>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>>>> the messages printed to serial which is what's slowing you down.
>>>>
>>>> The other problem sounds pretty severe, but the only thing your patch
>>>> does any different from the current code flow would be the patch below.
>>>> Or did I miss anything?
>>>>
>>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>>> index 5cc2e7a..4672bc2 100644
>>>> --- a/arch/powerpc/kvm/emulate.c
>>>> +++ b/arch/powerpc/kvm/emulate.c
>>>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run
>>>> *run,
>>>> struct kvm_vcpu *vcpu)
>>>>                          advance = 0;
>>>>                          printk(KERN_ERR "Couldn't emulate instruction
>>>> 0x%08x "
>>>>                                 "(op %d xop %d)\n", inst, get_op(inst),
>>>> get_xop(inst));
>>>> +#ifdef CONFIG_PPC_BOOK3S
>>>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>> +#else
>>>>                          kvmppc_core_queue_program(vcpu, 0);
>>>> +#endif
>>>>                  }
>>>>          }
>>>>
>> Do you want I send an updated patch with your changes?
> 
> Well, you reported the issue and narrowed it down, so feel free to send
> it under your name :). I merely simplified your patch a bit.

Well, while I was trying to update the patch, I've re-tested this... and
it fails. I don't know what I'm doing bad now or what I did bad before
but it seems it doesn't work. :(

Thomas, could try the patch from Alex?

I'm trying to understand what happens...

Laurent

Re: [PATCH] kvm-pr: manage illegal instructions

[Thomas Huth]

On 17.05.2016 19:49, Laurent Vivier wrote:
> 
> 
> On 17/05/2016 10:37, Alexander Graf wrote:
>> On 05/17/2016 10:35 AM, Laurent Vivier wrote:
>>>
>>> On 12/05/2016 16:23, Laurent Vivier wrote:
>>>>
>>>> On 12/05/2016 11:27, Alexander Graf wrote:
>>>>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>>>>> While writing some instruction tests for kvm-unit-tests for
>>>>>>>>>> powerpc,
>>>>>>>>>> I've found that illegal instructions are not managed correctly
>>>>>>>>>> with
>>>>>>>>>> kvm-pr,
>>>>>>>>>> while it is fine with kvm-hv.
>>>>>>>>>>
>>>>>>>>>> When an illegal instruction (like ".long 0") is processed by
>>>>>>>>>> kvm-pr,
>>>>>>>>>> the kernel logs are filled with:
>>>>>>>>>>
>>>>>>>>>>          Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>>>>          kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>>>>
>>>>>>>>>> While the exception handler receives an interrupt for each
>>>>>>>>>> instruction
>>>>>>>>>> executed after the illegal instruction.
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>>>>> ---
>>>>>>>>>>      arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>>>>      1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>> *run,
>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>            switch (get_op(inst)) {
>>>>>>>>>>          case 0:
>>>>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>>>>              if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>>>>                  (inst == swab32(inst_sc))) {
>>>>>>>>>>                  /*
>>>>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>> *run,
>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>                  kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>>>>                  kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>>>>                  emulated = EMULATE_DONE;
>>>>>>>>>> +        } else {
>>>>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is?
>>>>>>>>> Fixing it
>>>>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>>>>
>>>>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>>>>> wrong
>>>>>>>>> spot or are the log messages the problem?
>>>>>>>> No, the problem is the host kernel logs are filled by the message
>>>>>>>> and
>>>>>>>> the execution hangs. And the host becomes unresponsiveness, even
>>>>>>>> after
>>>>>>>> the end of the tests.
>>>>>>>>
>>>>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR
>>>>>>>> host,
>>>>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>>>>> Ok, so the log messages are the problem. Please fix the message
>>>>>>> output
>>>>>>> then - or remove it altogether. Or if you like, create a module
>>>>>>> parameter that allows you to emit them.
>>>>>>>
>>>>>>> I personally think the best solution would be to just convert the
>>>>>>> message into a trace point.
>>>>>>>
>>>>>>> While at it, please see whether the guest can trigger similar host
>>>>>>> log
>>>>>>> output excess in other code paths.
>>>>>> The problem is not really with the log messages: they are
>>>>>> consequence of
>>>>>> the bug I try to fix.
>>>>>>
>>>>>> What happens is once kvm_pr decodes an invalid instruction all the
>>>>>> valid
>>>>>> following instructions trigger a Program exception to the guest
>>>>>> (but are
>>>>>> executed correctly). It has no real consequence on big machine like
>>>>>> POWER8, except that the guest become very slow and the log files of
>>>>>> the
>>>>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>>>>> smaller machine like a  PowerMac G5, the machine becomes simply
>>>>>> unusable.
>>>>> It's probably more related to your verbosity level of kernel messages.
>>>>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>>>>> the messages printed to serial which is what's slowing you down.
>>>>>
>>>>> The other problem sounds pretty severe, but the only thing your patch
>>>>> does any different from the current code flow would be the patch below.
>>>>> Or did I miss anything?
>>>>>
>>>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>>>> index 5cc2e7a..4672bc2 100644
>>>>> --- a/arch/powerpc/kvm/emulate.c
>>>>> +++ b/arch/powerpc/kvm/emulate.c
>>>>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run
>>>>> *run,
>>>>> struct kvm_vcpu *vcpu)
>>>>>                          advance = 0;
>>>>>                          printk(KERN_ERR "Couldn't emulate instruction
>>>>> 0x%08x "
>>>>>                                 "(op %d xop %d)\n", inst, get_op(inst),
>>>>> get_xop(inst));
>>>>> +#ifdef CONFIG_PPC_BOOK3S
>>>>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>> +#else
>>>>>                          kvmppc_core_queue_program(vcpu, 0);
>>>>> +#endif
>>>>>                  }
>>>>>          }
>>>>>
>>> Do you want I send an updated patch with your changes?
>>
>> Well, you reported the issue and narrowed it down, so feel free to send
>> it under your name :). I merely simplified your patch a bit.
> 
> Well, while I was trying to update the patch, I've re-tested this... and
> it fails. I don't know what I'm doing bad now or what I did bad before
> but it seems it doesn't work. :(
> 
> Thomas, could try the patch from Alex?

The patch from Alex also does not work for me.

What's that difference with SRR1_PROGILL anyway, how should that prevent
the endless messages?

 Thomas

Re: [PATCH] kvm-pr: manage illegal instructions

[Thomas Huth]

On 18.05.2016 12:18, Thomas Huth wrote:
> On 17.05.2016 19:49, Laurent Vivier wrote:
>>
>>
>> On 17/05/2016 10:37, Alexander Graf wrote:
>>> On 05/17/2016 10:35 AM, Laurent Vivier wrote:
>>>>
>>>> On 12/05/2016 16:23, Laurent Vivier wrote:
>>>>>
>>>>> On 12/05/2016 11:27, Alexander Graf wrote:
>>>>>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>>>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>>>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>>>>>> While writing some instruction tests for kvm-unit-tests for
>>>>>>>>>>> powerpc,
>>>>>>>>>>> I've found that illegal instructions are not managed correctly
>>>>>>>>>>> with
>>>>>>>>>>> kvm-pr,
>>>>>>>>>>> while it is fine with kvm-hv.
>>>>>>>>>>>
>>>>>>>>>>> When an illegal instruction (like ".long 0") is processed by
>>>>>>>>>>> kvm-pr,
>>>>>>>>>>> the kernel logs are filled with:
>>>>>>>>>>>
>>>>>>>>>>>          Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>>>>>          kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>>>>>
>>>>>>>>>>> While the exception handler receives an interrupt for each
>>>>>>>>>>> instruction
>>>>>>>>>>> executed after the illegal instruction.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>>>>>> ---
>>>>>>>>>>>      arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>>>>>      1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>>>>
>>>>>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>>> *run,
>>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>>            switch (get_op(inst)) {
>>>>>>>>>>>          case 0:
>>>>>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>>>>>              if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>>>>>                  (inst == swab32(inst_sc))) {
>>>>>>>>>>>                  /*
>>>>>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>>> *run,
>>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>>                  kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>>>>>                  kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>>>>>                  emulated = EMULATE_DONE;
>>>>>>>>>>> +        } else {
>>>>>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is?
>>>>>>>>>> Fixing it
>>>>>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>>>>>
>>>>>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>>>>>> wrong
>>>>>>>>>> spot or are the log messages the problem?
>>>>>>>>> No, the problem is the host kernel logs are filled by the message
>>>>>>>>> and
>>>>>>>>> the execution hangs. And the host becomes unresponsiveness, even
>>>>>>>>> after
>>>>>>>>> the end of the tests.
>>>>>>>>>
>>>>>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR
>>>>>>>>> host,
>>>>>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>>>>>> Ok, so the log messages are the problem. Please fix the message
>>>>>>>> output
>>>>>>>> then - or remove it altogether. Or if you like, create a module
>>>>>>>> parameter that allows you to emit them.
>>>>>>>>
>>>>>>>> I personally think the best solution would be to just convert the
>>>>>>>> message into a trace point.
>>>>>>>>
>>>>>>>> While at it, please see whether the guest can trigger similar host
>>>>>>>> log
>>>>>>>> output excess in other code paths.
>>>>>>> The problem is not really with the log messages: they are
>>>>>>> consequence of
>>>>>>> the bug I try to fix.
>>>>>>>
>>>>>>> What happens is once kvm_pr decodes an invalid instruction all the
>>>>>>> valid
>>>>>>> following instructions trigger a Program exception to the guest
>>>>>>> (but are
>>>>>>> executed correctly). It has no real consequence on big machine like
>>>>>>> POWER8, except that the guest become very slow and the log files of
>>>>>>> the
>>>>>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>>>>>> smaller machine like a  PowerMac G5, the machine becomes simply
>>>>>>> unusable.
>>>>>> It's probably more related to your verbosity level of kernel messages.
>>>>>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>>>>>> the messages printed to serial which is what's slowing you down.
>>>>>>
>>>>>> The other problem sounds pretty severe, but the only thing your patch
>>>>>> does any different from the current code flow would be the patch below.
>>>>>> Or did I miss anything?
>>>>>>
>>>>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>>>>> index 5cc2e7a..4672bc2 100644
>>>>>> --- a/arch/powerpc/kvm/emulate.c
>>>>>> +++ b/arch/powerpc/kvm/emulate.c
>>>>>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run
>>>>>> *run,
>>>>>> struct kvm_vcpu *vcpu)
>>>>>>                          advance = 0;
>>>>>>                          printk(KERN_ERR "Couldn't emulate instruction
>>>>>> 0x%08x "
>>>>>>                                 "(op %d xop %d)\n", inst, get_op(inst),
>>>>>> get_xop(inst));
>>>>>> +#ifdef CONFIG_PPC_BOOK3S
>>>>>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>> +#else
>>>>>>                          kvmppc_core_queue_program(vcpu, 0);
>>>>>> +#endif
>>>>>>                  }
>>>>>>          }
>>>>>>
>>>> Do you want I send an updated patch with your changes?
>>>
>>> Well, you reported the issue and narrowed it down, so feel free to send
>>> it under your name :). I merely simplified your patch a bit.
>>
>> Well, while I was trying to update the patch, I've re-tested this... and
>> it fails. I don't know what I'm doing bad now or what I did bad before
>> but it seems it doesn't work. :(
>>
>> Thomas, could try the patch from Alex?
> 
> The patch from Alex also does not work for me.

I've now had a closer look at the code, and I think the endless loop is
caused by the fact that we try to inject a program interrupt twice here.

In kvmppc_handle_exit_pr(), the code flow looks like this:

	case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
	{
		...
		er = kvmppc_emulate_instruction(run, vcpu);
		switch (er) {
			...
		case EMULATE_FAIL:
			printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",
			       __func__, kvmppc_get_pc(vcpu), last_inst);
			kvmppc_core_queue_program(vcpu, flags);
			printk(KERN_CRIT "%s: pc = %lx \n",
			       __func__, kvmppc_get_pc(vcpu));
			r = RESUME_GUEST;
			break;
		...
	}

But when you look at the end of kvmppc_emulate_instruction(), you
can see that the interrupt has also already been injected there:

	if (emulated == EMULATE_FAIL) {
		emulated = vcpu->kvm->arch.kvm_ops->emulate_op(run, vcpu, inst,
							       &advance);
		if (emulated == EMULATE_AGAIN) {
			advance = 0;
		} else if (emulated == EMULATE_FAIL) {
			advance = 0;
			printk(KERN_ERR "Couldn't emulate instruction 0x%08x "
			       "(op %d xop %d)\n", inst, get_op(inst), get_xop(inst));
			kvmppc_core_queue_program(vcpu, 0);
		}
	}

Injecting the program interrupt twice of course destroys the
return address in SRR0, causing this strange behavior.
If I comment out the kvmppc_core_queue_program() in
kvmppc_emulate_instruction(), the endless loop is gone.

 Thomas

Re: [PATCH] kvm-pr: manage illegal instructions

[Thomas Huth]

On 18.05.2016 12:53, Thomas Huth wrote:
> On 18.05.2016 12:18, Thomas Huth wrote:
>> On 17.05.2016 19:49, Laurent Vivier wrote:
>>>
>>>
>>> On 17/05/2016 10:37, Alexander Graf wrote:
>>>> On 05/17/2016 10:35 AM, Laurent Vivier wrote:
>>>>>
>>>>> On 12/05/2016 16:23, Laurent Vivier wrote:
>>>>>>
>>>>>> On 12/05/2016 11:27, Alexander Graf wrote:
>>>>>>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>>>>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>>>>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>>>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>>>>>>> While writing some instruction tests for kvm-unit-tests for
>>>>>>>>>>>> powerpc,
>>>>>>>>>>>> I've found that illegal instructions are not managed correctly
>>>>>>>>>>>> with
>>>>>>>>>>>> kvm-pr,
>>>>>>>>>>>> while it is fine with kvm-hv.
>>>>>>>>>>>>
>>>>>>>>>>>> When an illegal instruction (like ".long 0") is processed by
>>>>>>>>>>>> kvm-pr,
>>>>>>>>>>>> the kernel logs are filled with:
>>>>>>>>>>>>
>>>>>>>>>>>>          Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>>>>>>          kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>>>>>>
>>>>>>>>>>>> While the exception handler receives an interrupt for each
>>>>>>>>>>>> instruction
>>>>>>>>>>>> executed after the illegal instruction.
>>>>>>>>>>>>
>>>>>>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>>>>>>> ---
>>>>>>>>>>>>      arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>>>>>>      1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>>>>>
>>>>>>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>>>> *run,
>>>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>>>            switch (get_op(inst)) {
>>>>>>>>>>>>          case 0:
>>>>>>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>>>>>>              if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>>>>>>                  (inst == swab32(inst_sc))) {
>>>>>>>>>>>>                  /*
>>>>>>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>>>> *run,
>>>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>>>                  kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>>>>>>                  kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>>>>>>                  emulated = EMULATE_DONE;
>>>>>>>>>>>> +        } else {
>>>>>>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is?
>>>>>>>>>>> Fixing it
>>>>>>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>>>>>>
>>>>>>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>>>>>>> wrong
>>>>>>>>>>> spot or are the log messages the problem?
>>>>>>>>>> No, the problem is the host kernel logs are filled by the message
>>>>>>>>>> and
>>>>>>>>>> the execution hangs. And the host becomes unresponsiveness, even
>>>>>>>>>> after
>>>>>>>>>> the end of the tests.
>>>>>>>>>>
>>>>>>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR
>>>>>>>>>> host,
>>>>>>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>>>>>>> Ok, so the log messages are the problem. Please fix the message
>>>>>>>>> output
>>>>>>>>> then - or remove it altogether. Or if you like, create a module
>>>>>>>>> parameter that allows you to emit them.
>>>>>>>>>
>>>>>>>>> I personally think the best solution would be to just convert the
>>>>>>>>> message into a trace point.
>>>>>>>>>
>>>>>>>>> While at it, please see whether the guest can trigger similar host
>>>>>>>>> log
>>>>>>>>> output excess in other code paths.
>>>>>>>> The problem is not really with the log messages: they are
>>>>>>>> consequence of
>>>>>>>> the bug I try to fix.
>>>>>>>>
>>>>>>>> What happens is once kvm_pr decodes an invalid instruction all the
>>>>>>>> valid
>>>>>>>> following instructions trigger a Program exception to the guest
>>>>>>>> (but are
>>>>>>>> executed correctly). It has no real consequence on big machine like
>>>>>>>> POWER8, except that the guest become very slow and the log files of
>>>>>>>> the
>>>>>>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>>>>>>> smaller machine like a  PowerMac G5, the machine becomes simply
>>>>>>>> unusable.
>>>>>>> It's probably more related to your verbosity level of kernel messages.
>>>>>>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>>>>>>> the messages printed to serial which is what's slowing you down.
>>>>>>>
>>>>>>> The other problem sounds pretty severe, but the only thing your patch
>>>>>>> does any different from the current code flow would be the patch below.
>>>>>>> Or did I miss anything?
>>>>>>>
>>>>>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>>>>>> index 5cc2e7a..4672bc2 100644
>>>>>>> --- a/arch/powerpc/kvm/emulate.c
>>>>>>> +++ b/arch/powerpc/kvm/emulate.c
>>>>>>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run
>>>>>>> *run,
>>>>>>> struct kvm_vcpu *vcpu)
>>>>>>>                          advance = 0;
>>>>>>>                          printk(KERN_ERR "Couldn't emulate instruction
>>>>>>> 0x%08x "
>>>>>>>                                 "(op %d xop %d)\n", inst, get_op(inst),
>>>>>>> get_xop(inst));
>>>>>>> +#ifdef CONFIG_PPC_BOOK3S
>>>>>>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>> +#else
>>>>>>>                          kvmppc_core_queue_program(vcpu, 0);
>>>>>>> +#endif
>>>>>>>                  }
>>>>>>>          }
>>>>>>>
>>>>> Do you want I send an updated patch with your changes?
>>>>
>>>> Well, you reported the issue and narrowed it down, so feel free to send
>>>> it under your name :). I merely simplified your patch a bit.
>>>
>>> Well, while I was trying to update the patch, I've re-tested this... and
>>> it fails. I don't know what I'm doing bad now or what I did bad before
>>> but it seems it doesn't work. :(
>>>
>>> Thomas, could try the patch from Alex?
>>
>> The patch from Alex also does not work for me.
> 
> I've now had a closer look at the code, and I think the endless loop is
> caused by the fact that we try to inject a program interrupt twice here.
> 
> In kvmppc_handle_exit_pr(), the code flow looks like this:
> 
> 	case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
> 	{
> 		...
> 		er = kvmppc_emulate_instruction(run, vcpu);
> 		switch (er) {
> 			...
> 		case EMULATE_FAIL:
> 			printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",
> 			       __func__, kvmppc_get_pc(vcpu), last_inst);
> 			kvmppc_core_queue_program(vcpu, flags);
> 			printk(KERN_CRIT "%s: pc = %lx \n",
> 			       __func__, kvmppc_get_pc(vcpu));
> 			r = RESUME_GUEST;
> 			break;
> 		...
> 	}
> 
> But when you look at the end of kvmppc_emulate_instruction(), you
> can see that the interrupt has also already been injected there:
> 
> 	if (emulated == EMULATE_FAIL) {
> 		emulated = vcpu->kvm->arch.kvm_ops->emulate_op(run, vcpu, inst,
> 							       &advance);
> 		if (emulated == EMULATE_AGAIN) {
> 			advance = 0;
> 		} else if (emulated == EMULATE_FAIL) {
> 			advance = 0;
> 			printk(KERN_ERR "Couldn't emulate instruction 0x%08x "
> 			       "(op %d xop %d)\n", inst, get_op(inst), get_xop(inst));
> 			kvmppc_core_queue_program(vcpu, 0);
> 		}
> 	}
> 
> Injecting the program interrupt twice of course destroys the
> return address in SRR0, causing this strange behavior.
> If I comment out the kvmppc_core_queue_program() in
> kvmppc_emulate_instruction(), the endless loop is gone.

I've now also checked the other callers of kvmppc_emulate_instruction(),
and all are already trying to inject an interrupt on their own, so
removing the kvmppc_core_queue_program() from
kvmppc_emulate_instruction() sounds like the right solution for me.
I'll submit a corresponding patch...

 Thomas

Re: [PATCH] kvm-pr: manage illegal instructions

[Thomas Huth]

On 18.05.2016 12:53, Thomas Huth wrote:
> On 18.05.2016 12:18, Thomas Huth wrote:
>> On 17.05.2016 19:49, Laurent Vivier wrote:
>>>
>>>
>>> On 17/05/2016 10:37, Alexander Graf wrote:
>>>> On 05/17/2016 10:35 AM, Laurent Vivier wrote:
>>>>>
>>>>> On 12/05/2016 16:23, Laurent Vivier wrote:
>>>>>>
>>>>>> On 12/05/2016 11:27, Alexander Graf wrote:
>>>>>>> On 05/12/2016 11:10 AM, Laurent Vivier wrote:
>>>>>>>> On 11/05/2016 13:49, Alexander Graf wrote:
>>>>>>>>> On 05/11/2016 01:14 PM, Laurent Vivier wrote:
>>>>>>>>>> On 11/05/2016 12:35, Alexander Graf wrote:
>>>>>>>>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote:
>>>>>>>>>>>> While writing some instruction tests for kvm-unit-tests for
>>>>>>>>>>>> powerpc,
>>>>>>>>>>>> I've found that illegal instructions are not managed correctly
>>>>>>>>>>>> with
>>>>>>>>>>>> kvm-pr,
>>>>>>>>>>>> while it is fine with kvm-hv.
>>>>>>>>>>>>
>>>>>>>>>>>> When an illegal instruction (like ".long 0") is processed by
>>>>>>>>>>>> kvm-pr,
>>>>>>>>>>>> the kernel logs are filled with:
>>>>>>>>>>>>
>>>>>>>>>>>>          Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>>>>>>>>>>>          kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
>>>>>>>>>>>>
>>>>>>>>>>>> While the exception handler receives an interrupt for each
>>>>>>>>>>>> instruction
>>>>>>>>>>>> executed after the illegal instruction.
>>>>>>>>>>>>
>>>>>>>>>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>>>>>>>>>> ---
>>>>>>>>>>>>      arch/powerpc/kvm/book3s_emulate.c | 4 +++-
>>>>>>>>>>>>      1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>>>>>
>>>>>>>>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> index 2afdb9c..4ee969d 100644
>>>>>>>>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>>>>>>>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>>>> *run,
>>>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>>>            switch (get_op(inst)) {
>>>>>>>>>>>>          case 0:
>>>>>>>>>>>> -        emulated = EMULATE_FAIL;
>>>>>>>>>>>>              if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
>>>>>>>>>>>>                  (inst == swab32(inst_sc))) {
>>>>>>>>>>>>                  /*
>>>>>>>>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run
>>>>>>>>>>>> *run,
>>>>>>>>>>>> struct kvm_vcpu *vcpu,
>>>>>>>>>>>>                  kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
>>>>>>>>>>>>                  kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
>>>>>>>>>>>>                  emulated = EMULATE_DONE;
>>>>>>>>>>>> +        } else {
>>>>>>>>>>>> +            kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>>>>>> But isn't that exactly what the semantic of EMULATE_FAIL is?
>>>>>>>>>>> Fixing it
>>>>>>>>>>> up in book3s_emulate.c is definitely the wrong spot.
>>>>>>>>>>>
>>>>>>>>>>> So what is the problem you're trying to solve? Is the SRR0 at the
>>>>>>>>>>> wrong
>>>>>>>>>>> spot or are the log messages the problem?
>>>>>>>>>> No, the problem is the host kernel logs are filled by the message
>>>>>>>>>> and
>>>>>>>>>> the execution hangs. And the host becomes unresponsiveness, even
>>>>>>>>>> after
>>>>>>>>>> the end of the tests.
>>>>>>>>>>
>>>>>>>>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR
>>>>>>>>>> host,
>>>>>>>>>> and check the kernel logs (dmesg), then try to ssh to the host...
>>>>>>>>> Ok, so the log messages are the problem. Please fix the message
>>>>>>>>> output
>>>>>>>>> then - or remove it altogether. Or if you like, create a module
>>>>>>>>> parameter that allows you to emit them.
>>>>>>>>>
>>>>>>>>> I personally think the best solution would be to just convert the
>>>>>>>>> message into a trace point.
>>>>>>>>>
>>>>>>>>> While at it, please see whether the guest can trigger similar host
>>>>>>>>> log
>>>>>>>>> output excess in other code paths.
>>>>>>>> The problem is not really with the log messages: they are
>>>>>>>> consequence of
>>>>>>>> the bug I try to fix.
>>>>>>>>
>>>>>>>> What happens is once kvm_pr decodes an invalid instruction all the
>>>>>>>> valid
>>>>>>>> following instructions trigger a Program exception to the guest
>>>>>>>> (but are
>>>>>>>> executed correctly). It has no real consequence on big machine like
>>>>>>>> POWER8, except that the guest become very slow and the log files of
>>>>>>>> the
>>>>>>>> host are filled with messages (and qemu uses 100% of the CPU). On a
>>>>>>>> smaller machine like a  PowerMac G5, the machine becomes simply
>>>>>>>> unusable.
>>>>>>> It's probably more related to your verbosity level of kernel messages.
>>>>>>> If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get
>>>>>>> the messages printed to serial which is what's slowing you down.
>>>>>>>
>>>>>>> The other problem sounds pretty severe, but the only thing your patch
>>>>>>> does any different from the current code flow would be the patch below.
>>>>>>> Or did I miss anything?
>>>>>>>
>>>>>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>>>>>> index 5cc2e7a..4672bc2 100644
>>>>>>> --- a/arch/powerpc/kvm/emulate.c
>>>>>>> +++ b/arch/powerpc/kvm/emulate.c
>>>>>>> @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run
>>>>>>> *run,
>>>>>>> struct kvm_vcpu *vcpu)
>>>>>>>                          advance = 0;
>>>>>>>                          printk(KERN_ERR "Couldn't emulate instruction
>>>>>>> 0x%08x "
>>>>>>>                                 "(op %d xop %d)\n", inst, get_op(inst),
>>>>>>> get_xop(inst));
>>>>>>> +#ifdef CONFIG_PPC_BOOK3S
>>>>>>> +                       kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>>>>>> +#else
>>>>>>>                          kvmppc_core_queue_program(vcpu, 0);
>>>>>>> +#endif
>>>>>>>                  }
>>>>>>>          }
>>>>>>>
>>>>> Do you want I send an updated patch with your changes?
>>>>
>>>> Well, you reported the issue and narrowed it down, so feel free to send
>>>> it under your name :). I merely simplified your patch a bit.
>>>
>>> Well, while I was trying to update the patch, I've re-tested this... and
>>> it fails. I don't know what I'm doing bad now or what I did bad before
>>> but it seems it doesn't work. :(
>>>
>>> Thomas, could try the patch from Alex?
>>
>> The patch from Alex also does not work for me.
> 
> I've now had a closer look at the code, and I think the endless loop is
> caused by the fact that we try to inject a program interrupt twice here.
[...]
> Injecting the program interrupt twice of course destroys the
> return address in SRR0, causing this strange behavior.
> If I comment out the kvmppc_core_queue_program() in
> kvmppc_emulate_instruction(), the endless loop is gone.

Apart from this problem with injecting the program exception twice,
there is now another problem left here: In kvmppc_handle_exit_pr(), the
flags variable is 0, thus we're injecting the program exception without
indication what it is all about.
It works fine if I simply hard-code flags = SRR1_PROGILL, but I guess
that's not the right solution to this problem.

I'm currently trying to understand the call chain of this function, but
I have a hard time to understand why we don't get a proper value in this
case...
Alex (or somebody else who's more familiar with this code), do you have
an idea why flags could be zero here?

 Thomas