Re: [PATCH v3] kvm-vfio: do not use module_init

From: Alex Williamson
Date: Wed Sep 24 2014 - 11:41:46 EST


On Wed, 2014-09-24 at 14:09 +0200, 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@xxxxxxx>
> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
> Cc: Alex Williamson <Alex.Williamson@xxxxxxxxxx>
> Fixes: 80ce1639727e9d38729c34f162378508c307ca25
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> virt/kvm/kvm_main.c | 4 ++++
> virt/kvm/vfio.c | 4 ++--
> virt/kvm/vfio.h | 13 +++++++++++++
> 3 files changed, 19 insertions(+), 2 deletions(-)
> create mode 100644 virt/kvm/vfio.h

Thanks Paolo

Acked-by: Alex Williamson <alex.williamson@xxxxxxxxxx>

> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index db57363cc287..499db0977f3c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -57,6 +57,7 @@
>
> #include "coalesced_mmio.h"
> #include "async_pf.h"
> +#include "vfio.h"
>
> #define CREATE_TRACE_POINTS
> #include <trace/events/kvm.h>
> @@ -3226,6 +3227,9 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
> goto out_undebugfs;
> }
>
> + r = kvm_vfio_ops_init();
> + WARN_ON(r);
> +
> return 0;
>
> out_undebugfs:
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index bb11b36ee8a2..281e7cf2b8e5 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -18,6 +18,7 @@
> #include <linux/slab.h>
> #include <linux/uaccess.h>
> #include <linux/vfio.h>
> +#include "vfio.h"
>
> struct kvm_vfio_group {
> struct list_head node;
> @@ -278,8 +279,7 @@ static int kvm_vfio_create(struct kvm_device *dev, u32 type)
> return 0;
> }
>
> -static int __init kvm_vfio_ops_init(void)
> +int kvm_vfio_ops_init(void)
> {
> return kvm_register_device_ops(&kvm_vfio_ops, KVM_DEV_TYPE_VFIO);
> }
> -module_init(kvm_vfio_ops_init);
> diff --git a/virt/kvm/vfio.h b/virt/kvm/vfio.h
> new file mode 100644
> index 000000000000..92eac75d6b62
> --- /dev/null
> +++ b/virt/kvm/vfio.h
> @@ -0,0 +1,13 @@
> +#ifndef __KVM_VFIO_H
> +#define __KVM_VFIO_H
> +
> +#ifdef CONFIG_KVM_VFIO
> +int kvm_vfio_ops_init(void);
> +#else
> +static inline int kvm_vfio_ops_init(void)
> +{
> + return 0;
> +}
> +#endif
> +
> +#endif



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