Re: [Qemu-devel] [PATCH 05/17] kvm: add kvm stub for arch specific stuff

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-05-03 16:17, Alexander Graf wrote:
> 
> On 18.04.2011, at 20:34, Aurelien Jarno wrote:
> 
>> On Fri, Apr 15, 2011 at 05:32:46PM +0200, Alexander Graf wrote:
>>> We have a generic stub architecture for kvm calls, but some architectures
>>> are different from others. So we do want to be able to have stubs for
>>> architecture specific functionality as well.
>>>
>>> This patch adds kvm stubs for all architectures.
>>>
>>> Signed-off-by: Alexander Graf <agraf@suse.de>
>>> ---
>>> Makefile.target                   |    2 +-
>>> target-alpha/kvm-arch-stub.c      |   26 +++++++++++++++++++++++++
>>> target-arm/kvm-arch-stub.c        |   26 +++++++++++++++++++++++++
>>> target-cris/kvm-arch-stub.c       |   26 +++++++++++++++++++++++++
>>> target-i386/kvm-arch-stub.c       |   26 +++++++++++++++++++++++++
>>> target-lm32/kvm-arch-stub.c       |   26 +++++++++++++++++++++++++
>>> target-m68k/kvm-arch-stub.c       |   26 +++++++++++++++++++++++++
>>> target-microblaze/kvm-arch-stub.c |   26 +++++++++++++++++++++++++
>>> target-mips/kvm-arch-stub.c       |   26 +++++++++++++++++++++++++
>>> target-ppc/kvm-arch-stub.c        |   26 +++++++++++++++++++++++++
>>> target-s390x/kvm-arch-stub.c      |   38 +++++++++++++++++++++++++++++++++++++
>>> target-sh4/kvm-arch-stub.c        |   26 +++++++++++++++++++++++++
>>> target-sparc/kvm-arch-stub.c      |   26 +++++++++++++++++++++++++
>>> target-unicore32/kvm-arch-stub.c  |   26 +++++++++++++++++++++++++
>>> 14 files changed, 351 insertions(+), 1 deletions(-)
>>> create mode 100644 target-alpha/kvm-arch-stub.c
>>> create mode 100644 target-arm/kvm-arch-stub.c
>>> create mode 100644 target-cris/kvm-arch-stub.c
>>> create mode 100644 target-i386/kvm-arch-stub.c
>>> create mode 100644 target-lm32/kvm-arch-stub.c
>>> create mode 100644 target-m68k/kvm-arch-stub.c
>>> create mode 100644 target-microblaze/kvm-arch-stub.c
>>> create mode 100644 target-mips/kvm-arch-stub.c
>>> create mode 100644 target-ppc/kvm-arch-stub.c
>>> create mode 100644 target-s390x/kvm-arch-stub.c
>>> create mode 100644 target-sh4/kvm-arch-stub.c
>>> create mode 100644 target-sparc/kvm-arch-stub.c
>>> create mode 100644 target-unicore32/kvm-arch-stub.c
>>
>> Do we really want to create so much files on architectures we will never
>> see KVM support? Actually I know very few things about KVM, so it would
>> be better to have this patch reviewed by someone else. Avi or Anthony
>> maybe?
> 
> Well, the main idea is to be able to have a unified place to put stub functions into. And as it stands with most generalizations, we either make it generic or not :).
> Maybe there's some Makefile magic to only compile the stub if the file exists? I certainly don't know of any.

This approach looks wrong.

The point of kvm stubs is to allow generic components to be built
independently of kvm enabled/disabled. But target-specific callbacks
can't be part of generic components anyway. So there is no need for a
stub, those bits will be built per-target anyway.

The examples you provided with this patch underline it:
s390-virtio-bus.c should be built for s390 but nothing else.

Jan

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