Re: [Xen-devel] [PATCH v2 01/15] xen/arm: register mmio handler at runtime

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

 Hi Julien,

On Fri, Apr 4, 2014 at 6:00 PM, Vijay Kilari <vijay.kilari@xxxxxxxxx> wrote:
> On Fri, Apr 4, 2014 at 5:48 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
>> Hello vijay,
>>
>> Thank your for the patch.
>>
>> On 04/04/2014 12:56 PM, vijay.kilari@xxxxxxxxx wrote:
>>
>> [..]
>>
>>> -#define MMIO_HANDLER_NR ARRAY_SIZE(mmio_handlers)
>>> +static DEFINE_SPINLOCK(handler_lock);
>>
>> Why a global lock rather than a domain lock?
>>
> OK can move into domain io_handler structure
>
>> [..]
>>
>>> +
>>> +void register_mmio_handler(struct domain *d, struct mmio_handler * handle)
>>> +{
>>> +    unsigned long flags;
>>> +    struct io_handler *handler = d->arch.io_handlers;
>>> +    BUG_ON(handler->num_entries >= MAX_IO_HANDLER);
>>> +
>>> +    spin_lock_irqsave(&handler_lock, flags);
>>
>> You don't need to disable the IRQ here.
>   My first version is without IRQ disable. I remember Andrii suggested it
>>
>>> +    handler->mmio_handlers[handler->num_entries++] = handle;
>>> +    spin_unlock_irqrestore(&handler_lock, flags);
>>> +}
>>>  /*
>>>   * Local variables:
>>>   * mode: C
>>> diff --git a/xen/arch/arm/io.h b/xen/arch/arm/io.h
>>> index 8d252c0..5fc1660 100644
>>> --- a/xen/arch/arm/io.h
>>> +++ b/xen/arch/arm/io.h
>>
>> As you are modifying this header. Can you move it in include/asm-arm?
> OK.
>
>>
>>> @@ -40,10 +40,14 @@ struct mmio_handler {
>>>      mmio_write_t write_handler;
>>>  };
>>>
>>> -extern const struct mmio_handler vgic_distr_mmio_handler;
>>> -extern const struct mmio_handler vuart_mmio_handler;
>>> +#define MAX_IO_HANDLER  16
>>> +struct io_handler {
>>> +    int num_entries;
>>> +    struct mmio_handler *mmio_handlers[MAX_IO_HANDLER];
>>> +};
>>>
>>>  extern int handle_mmio(mmio_info_t *info);
>>> +void register_mmio_handler(struct domain *d, struct mmio_handler * handle);
>>
>> As I said on the previous version, it would be nice to remove check
>> callback in the mmio_handler and replace it by addr/size. It's better if
>> we might want to change the place in the memory following the guest.
>>
>> So the result function would be:
>>
>> register_mmio_handler(struct domain *d, read_t read, write_t write,
>> addr, size);
>>
> OK.
   Though you suggested, I kept this check handler because it gives flexibility
for driver to make additional checks if required apart from just checking for
address range.

>>>
>>>  #endif

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