Re: [PATCH kvmtool 01/21] ioport: Remove ioport__setup_arch()

[Alexandru Elisei <alexandru.elisei@arm.com>]

Hi Andre,

On 2/22/21 10:23 AM, Andre Przywara wrote:
> On Wed, 17 Feb 2021 16:46:47 +0000
> Andre Przywara <andre.przywara@arm.com> wrote:
>
>> On Thu, 11 Feb 2021 17:32:01 +0000
>> Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>>
>> Hi,
>>
>>> On 2/11/21 5:16 PM, Andre Przywara wrote:  
>>>> On Wed, 10 Feb 2021 17:44:59 +0000
>>>> Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>>>>
>>>> Hi Alex,
>>>>    
>>>>> On 12/10/20 2:28 PM, Andre Przywara wrote:    
>>>>>> Since x86 had a special need for registering tons of special I/O ports,
>>>>>> we had an ioport__setup_arch() callback, to allow each architecture
>>>>>> to do the same. As it turns out no one uses it beside x86, so we remove
>>>>>> that unnecessary abstraction.
>>>>>>
>>>>>> The generic function was registered via a device_base_init() call, so
>>>>>> we just do the same for the x86 specific function only, and can remove
>>>>>> the unneeded ioport__setup_arch().
>>>>>>
>>>>>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>>>>>> ---
>>>>>>  arm/ioport.c         |  5 -----
>>>>>>  include/kvm/ioport.h |  1 -
>>>>>>  ioport.c             | 28 ----------------------------
>>>>>>  mips/kvm.c           |  5 -----
>>>>>>  powerpc/ioport.c     |  6 ------
>>>>>>  x86/ioport.c         | 25 ++++++++++++++++++++++++-
>>>>>>  6 files changed, 24 insertions(+), 46 deletions(-)
>>>>>>
>>>>>> diff --git a/arm/ioport.c b/arm/ioport.c
>>>>>> index 2f0feb9a..24092c9d 100644
>>>>>> --- a/arm/ioport.c
>>>>>> +++ b/arm/ioport.c
>>>>>> @@ -1,11 +1,6 @@
>>>>>>  #include "kvm/ioport.h"
>>>>>>  #include "kvm/irq.h"
>>>>>>  
>>>>>> -int ioport__setup_arch(struct kvm *kvm)
>>>>>> -{
>>>>>> -	return 0;
>>>>>> -}
>>>>>> -
>>>>>>  void ioport__map_irq(u8 *irq)
>>>>>>  {
>>>>>>  	*irq = irq__alloc_line();
>>>>>> diff --git a/include/kvm/ioport.h b/include/kvm/ioport.h
>>>>>> index 039633f7..d0213541 100644
>>>>>> --- a/include/kvm/ioport.h
>>>>>> +++ b/include/kvm/ioport.h
>>>>>> @@ -35,7 +35,6 @@ struct ioport_operations {
>>>>>>  							    enum irq_type));
>>>>>>  };
>>>>>>  
>>>>>> -int ioport__setup_arch(struct kvm *kvm);
>>>>>>  void ioport__map_irq(u8 *irq);
>>>>>>  
>>>>>>  int __must_check ioport__register(struct kvm *kvm, u16 port, struct ioport_operations *ops,
>>>>>> diff --git a/ioport.c b/ioport.c
>>>>>> index 844a832d..667e8386 100644
>>>>>> --- a/ioport.c
>>>>>> +++ b/ioport.c
>>>>>> @@ -158,21 +158,6 @@ int ioport__unregister(struct kvm *kvm, u16 port)
>>>>>>  	return 0;
>>>>>>  }
>>>>>>  
>>>>>> -static void ioport__unregister_all(void)
>>>>>> -{
>>>>>> -	struct ioport *entry;
>>>>>> -	struct rb_node *rb;
>>>>>> -	struct rb_int_node *rb_node;
>>>>>> -
>>>>>> -	rb = rb_first(&ioport_tree);
>>>>>> -	while (rb) {
>>>>>> -		rb_node = rb_int(rb);
>>>>>> -		entry = ioport_node(rb_node);
>>>>>> -		ioport_unregister(&ioport_tree, entry);
>>>>>> -		rb = rb_first(&ioport_tree);
>>>>>> -	}
>>>>>> -}      
>>>>> I get the impression this is a rebasing artifact. The commit message doesn't
>>>>> mention anything about removing ioport__exit() -> ioport__unregister_all(), and as
>>>>> far as I can tell it's still needed because there are places other than
>>>>> ioport__setup_arch() from where ioport__register() is called.    
>>>> I agree that the commit message is a bit thin on this fact, but the
>>>> functionality of ioport__unregister_all() is now in
>>>> x86/ioport.c:ioport__remove_arch(). I think removing ioport__init()
>>>> without removing ioport__exit() as well would look very weird, if not
>>>> hackish.    
>>> Not necessarily. ioport__unregister_all() removes the ioports added by
>>> x86/ioport.c::ioport__setup_arch(), *plus* ioports added by different devices,
>>> like serial, rtc, virtio-pci and vfio-pci (which are used by arm/arm64).  
>> Right, indeed. Not that it really matters, since we are about to exit
>> anyway, but it looks indeed I need to move this to a generic teardown
>> method, or actually just keep that part here in this file.
>>
>> Will give this a try.
> Well, now having a closer look I needed to remove this from here,
> because this whole file will go away.
> To keep the current functionality, we would need to add it to mmio.c,
> and interestingly we don't do any kind of similar cleanup there for the
> MMIO regions (probably this is kvmtool exiting anyway, see above).

This is a very good point. If the MMIO emulation doesn't unregister each MMIO
region before exiting (and has never done that since it was implemented), then I
don't think there's a reason that we should add it now. After all, kvmtool will
terminate after calling dev_base_exit destructors, which will take care of
deallocating the entire process memory.

Thanks,

Alex

>
> I will see if I can introduce it there, for good measure.
>
> Cheers,
> Andre
>
>
>> Thanks!
>> Andre
>>
>>>> I can amend the commit message to mention this, or is there anything
>>>> else I missed?
>>>>
>>>> Cheers,
>>>> Andre
>>>>    
>>>>>> -
>>>>>>  static const char *to_direction(int direction)
>>>>>>  {
>>>>>>  	if (direction == KVM_EXIT_IO_IN)
>>>>>> @@ -220,16 +205,3 @@ out:
>>>>>>  
>>>>>>  	return !kvm->cfg.ioport_debug;
>>>>>>  }
>>>>>> -
>>>>>> -int ioport__init(struct kvm *kvm)
>>>>>> -{
>>>>>> -	return ioport__setup_arch(kvm);
>>>>>> -}
>>>>>> -dev_base_init(ioport__init);
>>>>>> -
>>>>>> -int ioport__exit(struct kvm *kvm)
>>>>>> -{
>>>>>> -	ioport__unregister_all();
>>>>>> -	return 0;
>>>>>> -}
>>>>>> -dev_base_exit(ioport__exit);
>>>>>> diff --git a/mips/kvm.c b/mips/kvm.c
>>>>>> index 26355930..e110e5d5 100644
>>>>>> --- a/mips/kvm.c
>>>>>> +++ b/mips/kvm.c
>>>>>> @@ -100,11 +100,6 @@ void kvm__irq_trigger(struct kvm *kvm, int irq)
>>>>>>  		die_perror("KVM_IRQ_LINE ioctl");
>>>>>>  }
>>>>>>  
>>>>>> -int ioport__setup_arch(struct kvm *kvm)
>>>>>> -{
>>>>>> -	return 0;
>>>>>> -}
>>>>>> -
>>>>>>  bool kvm__arch_cpu_supports_vm(void)
>>>>>>  {
>>>>>>  	return true;
>>>>>> diff --git a/powerpc/ioport.c b/powerpc/ioport.c
>>>>>> index 0c188b61..a5cff4ee 100644
>>>>>> --- a/powerpc/ioport.c
>>>>>> +++ b/powerpc/ioport.c
>>>>>> @@ -12,12 +12,6 @@
>>>>>>  
>>>>>>  #include <stdlib.h>
>>>>>>  
>>>>>> -int ioport__setup_arch(struct kvm *kvm)
>>>>>> -{
>>>>>> -	/* PPC has no legacy ioports to set up */
>>>>>> -	return 0;
>>>>>> -}
>>>>>> -
>>>>>>  void ioport__map_irq(u8 *irq)
>>>>>>  {
>>>>>>  }
>>>>>> diff --git a/x86/ioport.c b/x86/ioport.c
>>>>>> index 7ad7b8f3..8c5c7699 100644
>>>>>> --- a/x86/ioport.c
>>>>>> +++ b/x86/ioport.c
>>>>>> @@ -69,7 +69,7 @@ void ioport__map_irq(u8 *irq)
>>>>>>  {
>>>>>>  }
>>>>>>  
>>>>>> -int ioport__setup_arch(struct kvm *kvm)
>>>>>> +static int ioport__setup_arch(struct kvm *kvm)
>>>>>>  {
>>>>>>  	int r;
>>>>>>  
>>>>>> @@ -150,3 +150,26 @@ int ioport__setup_arch(struct kvm *kvm)
>>>>>>  
>>>>>>  	return 0;
>>>>>>  }
>>>>>> +dev_base_init(ioport__setup_arch);
>>>>>> +
>>>>>> +static int ioport__remove_arch(struct kvm *kvm)
>>>>>> +{
>>>>>> +	ioport__unregister(kvm, 0x510);
>>>>>> +	ioport__unregister(kvm, 0x402);
>>>>>> +	ioport__unregister(kvm, 0x03D5);
>>>>>> +	ioport__unregister(kvm, 0x03D4);
>>>>>> +	ioport__unregister(kvm, 0x0378);
>>>>>> +	ioport__unregister(kvm, 0x0278);
>>>>>> +	ioport__unregister(kvm, 0x00F0);
>>>>>> +	ioport__unregister(kvm, 0x00ED);
>>>>>> +	ioport__unregister(kvm, IOPORT_DBG);
>>>>>> +	ioport__unregister(kvm, 0x00C0);
>>>>>> +	ioport__unregister(kvm, 0x00A0);
>>>>>> +	ioport__unregister(kvm, 0x0092);
>>>>>> +	ioport__unregister(kvm, 0x0040);
>>>>>> +	ioport__unregister(kvm, 0x0020);
>>>>>> +	ioport__unregister(kvm, 0x0000);
>>>>>> +
>>>>>> +	return 0;
>>>>>> +}
>>>>>> +dev_base_exit(ioport__remove_arch);