Il 30/06/2014 11:21, Cornelia Huck ha scritto:
On Thu, 26 Jun 2014 18:30:16 +0100
Will Deacon <will.deacon@xxxxxxx> wrote:
kvm_ioctl_create_device currently has knowledge of all the device types
and their associated ops. This is fairly inflexible when adding support
for new in-kernel device emulations, so move what we currently have out
into a table, which can support dynamic registration of ops by new
drivers for virtual hardware.
I didn't try to port all current drivers over, as it's not always clear
which initialisation hook the ops should be registered from.
I like the general idea of registering the ops dynamically, some
comments below.
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
---
Hi guys,
I've just started writing a virtual IOMMU for the ARM SMMU and figured a
registration mechanism for kvm_device_ops would be a nice cleanup for
that.
Will
include/linux/kvm_host.h | 1 +
include/uapi/linux/kvm.h | 1 +
virt/kvm/kvm_main.c | 65 ++++++++++++++++++++++++++++--------------------
3 files changed, 40 insertions(+), 27 deletions(-)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e11d8f170a62..3b368166286f 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -949,6 +949,7 @@ struct kvm_device_attr {
#define KVM_DEV_VFIO_GROUP_DEL 2
#define KVM_DEV_TYPE_ARM_VGIC_V2 5
#define KVM_DEV_TYPE_FLIC 6
+#define KVM_DEV_TYPE_MAX 7
This means we always need to move this value once we introduce a new
kvm device type. Can't you keep it in a dynamic list instead of a
table? We just need to do the lookup during device creation anyway.
There's also this wonderful thing called enum. ;)
It would let Will keep the simpler code with an array, and autogenerate
KVM_DEV_TYPE_MAX.
/*
* ioctls for VM fds
+int kvm_register_device_ops(struct kvm_device_ops *ops, u32 type)
+{
+ if (type >= KVM_DEV_TYPE_MAX)
... then you can make this ARRAY_SIZE, which makes the code quite nice &
obvious.
Paolo
+ return -ENOSPC;
+
+ if (kvm_device_ops_table[type] != NULL)
+ return -EEXIST;
Checking for type collisions would be a bit more expensive with a list,
but I don't think it matters.
+
+ kvm_device_ops_table[type] = ops;
+ return 0;
+}
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