Re: [kvm-devel] [PATCH 3/3] KVM - add hypercall nr to kvm_run

[Anthony Liguori <anthony@codemonkey.ws>]

Avi Kivity wrote:
> Jeff Dike wrote:
>   
>> Add the hypercall number to kvm_run and initialize it.  This might be
>> considered API-changing, so I kept it separate.
>>
>> Signed-off-by: Jeff Dike <jdike@linux.intel.com>
>> --
>>  drivers/kvm/kvm_main.c |    1 +
>>  include/linux/kvm.h    |    1 +
>>  2 files changed, 2 insertions(+)
>>
>> Index: kvm/drivers/kvm/kvm_main.c
>> ===================================================================
>> --- kvm.orig/drivers/kvm/kvm_main.c
>> +++ kvm/drivers/kvm/kvm_main.c
>> @@ -1361,6 +1361,7 @@ int kvm_hypercall(struct kvm_vcpu *vcpu,
>>  	}
>>  	switch (nr) {
>>  	default:
>> +		run->hypercall.nr = nr;
>>  		run->hypercall.args[0] = a0;
>>  		run->hypercall.args[1] = a1;
>>  		run->hypercall.args[2] = a2;
>> Index: kvm/include/linux/kvm.h
>> ===================================================================
>> --- kvm.orig/include/linux/kvm.h
>> +++ kvm/include/linux/kvm.h
>> @@ -106,6 +106,7 @@ struct kvm_run {
>>  		} mmio;
>>  		/* KVM_EXIT_HYPERCALL */
>>  		struct {
>> +			__u64 nr;
>>  			__u64 args[6];
>>  			__u64 ret;
>>  			__u32 longmode;
>>   
>>     
>
> It isn't API changing as the API could not be (and has not been) used.  
> We do need to add a padding element to the union to make sure additional 
> union members don't cause its size to change.
>
> Quite sad that we got this far with such brokenness.
>   

I'm planning on breaking this interface again since the new hypercall 
API only takes 4 arguments instead of 6.

Regards,

Anthony Liguori