Re: [PATCH 01/10] KVM: selftests: Take vcpu pointer instead of id in vm_vcpu_rm()

[Wainer dos Santos Moschetta]

On 4/14/20 5:25 AM, Andrew Jones wrote:
> On Mon, Apr 13, 2020 at 02:26:59PM -0700, Sean Christopherson wrote:
> > On Mon, Apr 13, 2020 at 03:26:55PM -0300, Wainer dos Santos Moschetta wrote:
> > > On 4/10/20 8:16 PM, Sean Christopherson wrote:
> > > > The sole caller of vm_vcpu_rm() already has the vcpu pointer, take it
> > > > directly instead of doing an extra lookup.
> > >
> > > Most of (if not all) vcpu related functions in kvm_util.c receives an id, so
> > > this change creates an inconsistency.
> > Ya, but taking the id is done out of "necessity", as everything is public
> > and for whatever reason the design of the selftest framework is to not
> > expose 'struct vcpu' outside of the utils.  vm_vcpu_rm() is internal only,
> > IMO pulling the id out of the vcpu just to lookup the same vcpu is a waste
> > of time.
> Agreed


Thanks Sean and Andrew for your comments. I'm not in position to 
change/propose any design of kvm selftests but even though I aimed to 
foster this discussion.

So, please, consider my Reviewed-by...

- Wainer


> > FWIW, I think the whole vcpuid thing is a bad interface, almost all the
> > tests end up defining an arbitrary number for the sole VCPU_ID, i.e. the
> > vcpuid interface just adds a pointless layer of obfuscation.  I haven't
> > looked through all the tests, but returning the vcpu and making the struct
> > opaque, same as kvm_vm, seems like it would yield more readable code with
> > less overhead.
> Agreed
>
> > While I'm on a soapbox, hiding 'struct vcpu' and 'struct kvm_vm' also seems
> > rather silly, but at least that doesn't directly lead to funky code.
> Agreed. While the concept has been slowly growing on me, I think accessor
> functions for each of the structs members are growing even faster...
>
> Thanks,
> drew
>
> > > Disregarding the above comment, the changes look good to me. So:
> > >
> > > Reviewed-by: Wainer dos Santos Moschetta <wainersm@xxxxxxxxxx>
> > >
> > >
> > > > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > > > ---
> > > >   tools/testing/selftests/kvm/lib/kvm_util.c | 7 +++----
> > > >   1 file changed, 3 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> > > > index 8a3523d4434f..9a783c20dd26 100644
> > > > --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> > > > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> > > > @@ -393,7 +393,7 @@ struct vcpu *vcpu_find(struct kvm_vm *vm, uint32_t vcpuid)
> > > >    *
> > > >    * Input Args:
> > > >    *   vm - Virtual Machine
> > > > - *   vcpuid - VCPU ID
> > > > + *   vcpu - VCPU to remove
> > > >    *
> > > >    * Output Args: None
> > > >    *
> > > > @@ -401,9 +401,8 @@ struct vcpu *vcpu_find(struct kvm_vm *vm, uint32_t vcpuid)
> > > >    *
> > > >    * Within the VM specified by vm, removes the VCPU given by vcpuid.
> > > >    */
> > > > -static void vm_vcpu_rm(struct kvm_vm *vm, uint32_t vcpuid)
> > > > +static void vm_vcpu_rm(struct kvm_vm *vm, struct vcpu *vcpu)
> > > >   {
> > > > -	struct vcpu *vcpu = vcpu_find(vm, vcpuid);
> > > >   	int ret;
> > > >   	ret = munmap(vcpu->state, sizeof(*vcpu->state));
> > > > @@ -427,7 +426,7 @@ void kvm_vm_release(struct kvm_vm *vmp)
> > > >   	int ret;
> > > >   	while (vmp->vcpu_head)
> > > > -		vm_vcpu_rm(vmp, vmp->vcpu_head->id);
> > > > +		vm_vcpu_rm(vmp, vmp->vcpu_head);
> > > >   	ret = close(vmp->fd);
> > > >   	TEST_ASSERT(ret == 0, "Close of vm fd failed,\n"