Re: [Xen-devel] [PATCH RFC v12 03/21] Remove an unnecessary assert from vmx_update_debug_state

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Mon, Sep 16, 2013 at 10:09 PM, Mukesh Rathor
<mukesh.rathor@xxxxxxxxxx> wrote:
> On Fri, 13 Sep 2013 17:25:03 +0100
> George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
>
>> As far as I can tell, there's nothing here that requires v to be
>> current.  vmx_update_exception_bitmap() is updated in other situations
>> where v!=current.
>>
>> Removing this allows the PVH code to call this during vmcs
>> construction in a later patch, making the code more robust by removing
>> duplicate code.
>>
>> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
>> CC: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
>> CC: Jan Beulich <jan.beulich@xxxxxxxx>
>> CC: Tim Deegan <tim@xxxxxxx>
>> CC: Keir Fraser <keir@xxxxxxx>
>> ---
>>  xen/arch/x86/hvm/vmx/vmx.c |    2 --
>>  1 file changed, 2 deletions(-)
>>
>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>> index 8ed7026..f02e47a 100644
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -1041,8 +1041,6 @@ void vmx_update_debug_state(struct vcpu *v)
>>  {
>>      unsigned long mask;
>>
>> -    ASSERT(v == current);
>> -
>>      mask = 1u << TRAP_int3;
>>      if ( !cpu_has_monitor_trap_flag )
>>          mask |= 1u << TRAP_debug;
>
>
> vmx_update_exception_bitmap() writes EXCEPTION_BITMAP of current vmcs,
> ie of current vcpu. If v != current, you'd be writing the bitmap of
> wrong vcpu. If the assertion is removed, then the function would need
> to vmx enter...

You mean, callers would need to call vmcs_enter before calling it.
Hmm... is there an assert for that?

 -George

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