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

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Mon, Jan 29, 2018 at 11:03 AM, Razvan Cojocaru
<rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 01/29/2018 07:58 PM, Tamas K Lengyel wrote:
>> On Mon, Jan 29, 2018 at 10:10 AM, Razvan Cojocaru
>> <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>> On exit, xen-access did not unsubscribe from CR4 write vm_events,
>>> potentially leaving the guest stuck.
>>>
>>> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>>> ---
>>>  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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