linux-kernel - Re: [PATCH v2] kvm-vfio: do not use module

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Date:	Wed, 24 Sep 2014 13:05:05 +0100
From:	Will Deacon <will.deacon@....com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Gleb Natapov <gleb@...nel.org>,
	Alex Williamson <Alex.Williamson@...hat.com>
Subject: Re: [PATCH v2] kvm-vfio: do not use module_init

On Wed, Sep 24, 2014 at 12:56:20PM +0100, Paolo Bonzini wrote:
> /me got confused between the kernel and QEMU.  In the kernel, you can
> only have one module_init function, and it will prevent unloading the
> module unless you also have the corresponding module_exit function.
> 
> So, commit 80ce1639727e (KVM: VFIO: register kvm_device_ops dynamically,
> 2014-09-02) broke unloading of the kvm module, by adding a module_init
> function and no module_exit.
> 
> Repair it by making kvm_vfio_ops_init weak, and checking it in
> kvm_init.
> 
> Cc: Will Deacon <will.deacon@....com>
> Cc: Gleb Natapov <gleb@...nel.org>
> Cc: Alex Williamson <Alex.Williamson@...hat.com>
> Fixes: 80ce1639727e9d38729c34f162378508c307ca25
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  virt/kvm/kvm_main.c | 9 +++++++++
>  virt/kvm/vfio.c     | 4 ++--
>  virt/kvm/vfio.h     | 6 ++++++
>  3 files changed, 17 insertions(+), 2 deletions(-)
>  create mode 100644 virt/kvm/vfio.h
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index db57363cc287..ad3439835adb 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -58,6 +58,10 @@
>  #include "coalesced_mmio.h"
>  #include "async_pf.h"
>  
> +#ifdef CONFIG_KVM_VFIO
> +#include "vfio.h"
> +#endif

Can't you include this unconditionally, then have the #ifdef in the header
and a static inline kvm_vfio_ops_init that returns 0?

Will
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