Re: [PATCH 2/7] KVM: arm: guest debug, define API headers

[Paolo Bonzini <pbonzini@redhat.com>]

On 26/11/2014 15:58, Alex Bennée wrote:
> 
> Andrew Jones <drjones@redhat.com> writes:
> 
>> On Tue, Nov 25, 2014 at 04:10:00PM +0000, Alex Bennée wrote:
>>> This commit defines the API headers for guest debugging. There are two
>>> architecture specific debug structures:
> <snip>
>>> +/* Architecture related debug defines - upper 16 bits of
>>> + * kvm_guest_debug->control
>>> + */
>>> +#define KVM_GUESTDBG_USE_SW_BP_SHIFT	16
>>> +#define KVM_GUESTDBG_USE_SW_BP		(1 << KVM_GUESTDBG_USE_SW_BP_SHIFT)
>>> +#define KVM_GUESTDBG_USE_HW_BP_SHIFT	17
>>> +#define KVM_GUESTDBG_USE_HW_BP		(1 << KVM_GUESTDBG_USE_HW_BP_SHIFT)
>>> +
>>
>> I see this are defined in arch/x86/include/uapi/asm/kvm.h,
>> so you needed to reproduce them here, but shouldn't they
>> be promoted to include/uapi/linux/kvm.h instead?
> 
> Well if we move them to common uapi we either restrict the $ARCH
> specific options that don't have SW/HW BKPTS (would be weird but...) or
> make them generic in the lower 16 bits (breaks API).
> 
> But in principle I have no objection if other don't.

I think it's a matter of personal taste.  "Architecture-specific" means
"not all architectures may support it", but it's certainly a good idea
to reuse the same value if multiple architectures do support a #define.

What you did is fine, another possibility is to do

    #define __KVM_GUESTDBG_USE_SW_BP   (1 << 16)

in include/uapi/linux/kvm.h, and

    #define KVM_GUESTDBG_USE_SW_BP __KVM_GUESTDBG_USE_SW_BP

in the arch-specific file.  Andrew, is this closer to what you intended?

Paolo