[PATCH] tests/xen-access: disable CR4 write events on application exit

[PATCH] tests/xen-access: disable CR4 write events on application exit

[Razvan Cojocaru]

On exit, xen-access did not unsubscribe from CR4 write vm_events,
potentially leaving the guest stuck.

Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
---
 tools/tests/xen-access/xen-access.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/tests/xen-access/xen-access.c b/tools/tests/xen-access/xen-access.c
index 9d960e2..c572550 100644
--- a/tools/tests/xen-access/xen-access.c
+++ b/tools/tests/xen-access/xen-access.c
@@ -654,6 +654,8 @@ int main(int argc, char *argv[])
                 rc = xc_monitor_cpuid(xch, domain_id, 0);
             if ( desc_access )
                 rc = xc_monitor_descriptor_access(xch, domain_id, 0);
+            if ( write_ctrlreg_cr4 )
+                rc = xc_monitor_write_ctrlreg(xch, domain_id, VM_EVENT_X86_CR4, 0, 1, 0, 1);
 
             if ( privcall )
                 rc = xc_monitor_privileged_call(xch, domain_id, 0);
-- 
2.7.4


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Re: [PATCH] tests/xen-access: disable CR4 write events on application exit

[Tamas K Lengyel]

On Mon, Jan 29, 2018 at 10:10 AM, Razvan Cojocaru
<rcojocaru@bitdefender.com> wrote:
> On exit, xen-access did not unsubscribe from CR4 write vm_events,
> potentially leaving the guest stuck.
>
> Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
> ---
>  tools/tests/xen-access/xen-access.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/tools/tests/xen-access/xen-access.c b/tools/tests/xen-access/xen-access.c
> index 9d960e2..c572550 100644
> --- a/tools/tests/xen-access/xen-access.c
> +++ b/tools/tests/xen-access/xen-access.c
> @@ -654,6 +654,8 @@ int main(int argc, char *argv[])
>                  rc = xc_monitor_cpuid(xch, domain_id, 0);
>              if ( desc_access )
>                  rc = xc_monitor_descriptor_access(xch, domain_id, 0);
> +            if ( write_ctrlreg_cr4 )
> +                rc = xc_monitor_write_ctrlreg(xch, domain_id, VM_EVENT_X86_CR4, 0, 1, 0, 1);

Any reason for the sync and onchangeonly parts to be set to 1 here? I
don't think it has any effect when you are disabling an event.

Tamas

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Re: [PATCH] tests/xen-access: disable CR4 write events on application exit

[Razvan Cojocaru]

On 01/29/2018 07:58 PM, Tamas K Lengyel wrote:
> On Mon, Jan 29, 2018 at 10:10 AM, Razvan Cojocaru
> <rcojocaru@bitdefender.com> wrote:
>> On exit, xen-access did not unsubscribe from CR4 write vm_events,
>> potentially leaving the guest stuck.
>>
>> Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
>> ---
>>  tools/tests/xen-access/xen-access.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/tools/tests/xen-access/xen-access.c b/tools/tests/xen-access/xen-access.c
>> index 9d960e2..c572550 100644
>> --- a/tools/tests/xen-access/xen-access.c
>> +++ b/tools/tests/xen-access/xen-access.c
>> @@ -654,6 +654,8 @@ int main(int argc, char *argv[])
>>                  rc = xc_monitor_cpuid(xch, domain_id, 0);
>>              if ( desc_access )
>>                  rc = xc_monitor_descriptor_access(xch, domain_id, 0);
>> +            if ( write_ctrlreg_cr4 )
>> +                rc = xc_monitor_write_ctrlreg(xch, domain_id, VM_EVENT_X86_CR4, 0, 1, 0, 1);
> 
> Any reason for the sync and onchangeonly parts to be set to 1 here? I
> don't think it has any effect when you are disabling an event.

Nope, they don't matter at all. I've just copied the "enable" line,
removed the mask so that the line would not go beyond 80 columns and
kept the rest as it was.

If the parameter after the index (VM_EVENT_X86_CR4) is 0, the others
don't matter.

But I can set them all to 0 if you prefer.


Thanks,
Razvan

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Re: [PATCH] tests/xen-access: disable CR4 write events on application exit

[Tamas K Lengyel]

On Mon, Jan 29, 2018 at 11:03 AM, Razvan Cojocaru
<rcojocaru@bitdefender.com> wrote:
> On 01/29/2018 07:58 PM, Tamas K Lengyel wrote:
>> On Mon, Jan 29, 2018 at 10:10 AM, Razvan Cojocaru
>> <rcojocaru@bitdefender.com> wrote:
>>> On exit, xen-access did not unsubscribe from CR4 write vm_events,
>>> potentially leaving the guest stuck.
>>>
>>> Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
>>> ---
>>>  tools/tests/xen-access/xen-access.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/tools/tests/xen-access/xen-access.c b/tools/tests/xen-access/xen-access.c
>>> index 9d960e2..c572550 100644
>>> --- a/tools/tests/xen-access/xen-access.c
>>> +++ b/tools/tests/xen-access/xen-access.c
>>> @@ -654,6 +654,8 @@ int main(int argc, char *argv[])
>>>                  rc = xc_monitor_cpuid(xch, domain_id, 0);
>>>              if ( desc_access )
>>>                  rc = xc_monitor_descriptor_access(xch, domain_id, 0);
>>> +            if ( write_ctrlreg_cr4 )
>>> +                rc = xc_monitor_write_ctrlreg(xch, domain_id, VM_EVENT_X86_CR4, 0, 1, 0, 1);
>>
>> Any reason for the sync and onchangeonly parts to be set to 1 here? I
>> don't think it has any effect when you are disabling an event.
>
> Nope, they don't matter at all. I've just copied the "enable" line,
> removed the mask so that the line would not go beyond 80 columns and
> kept the rest as it was.
>
> If the parameter after the index (VM_EVENT_X86_CR4) is 0, the others
> don't matter.
>
> But I can set them all to 0 if you prefer.

Just to keep things clean I would appreciate that.

Thanks,
Tamas

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