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Subject[PATCH 3/3] KVM: Move coalesced MMIO initialization (back) into kvm_create_vm()
Invoke kvm_coalesced_mmio_init() from kvm_create_vm() now that allocating
and initializing coalesced MMIO objects is separate from registering any
associated devices. Moving coalesced MMIO cleans up the last oddity
where KVM does VM creation/initialization after kvm_create_vm(), and more
importantly after kvm_arch_post_init_vm() is called and the VM is added
to the global vm_list, i.e. after the VM is fully created as far as KVM
is concerned.

Originally, kvm_coalesced_mmio_init() was called by kvm_create_vm(), but
the original implementation was completely devoid of error handling.
Commit 6ce5a090a9a0 ("KVM: coalesced_mmio: fix kvm_coalesced_mmio_init()'s
error handling" fixed the various bugs, and in doing so rightly moved the
call to after kvm_create_vm() because kvm_coalesced_mmio_init() also
registered the coalesced MMIO device. Commit 2b3c246a682c ("KVM: Make
coalesced mmio use a device per zone") cleaned up that mess by having
each zone register a separate device, i.e. moved device registration to
its logical home in kvm_vm_ioctl_register_coalesced_mmio(). As a result,
kvm_coalesced_mmio_init() is now a "pure" initialization helper and can
be safely called from kvm_create_vm().

Opportunstically drop the #ifdef, KVM provides stubs for
kvm_coalesced_mmio_{init,free}() when CONFIG_KVM_MMIO=n (arm).

Signed-off-by: Sean Christopherson <>
virt/kvm/kvm_main.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 15e304e059d4..44b92d773156 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1214,6 +1214,10 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
if (r)
goto out_err_no_mmu_notifier;

+ r = kvm_coalesced_mmio_init(kvm);
+ if (r < 0)
+ goto out_no_coalesced_mmio;
r = kvm_create_vm_debugfs(kvm, fdname);
if (r)
goto out_err_no_debugfs;
@@ -1234,6 +1238,8 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
+ kvm_coalesced_mmio_free(kvm);
if (kvm->mmu_notifier.ops)
mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
@@ -4907,11 +4913,6 @@ static int kvm_dev_ioctl_create_vm(unsigned long type)
goto put_fd;

- r = kvm_coalesced_mmio_init(kvm);
- if (r < 0)
- goto put_kvm;
file = anon_inode_getfile("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
if (IS_ERR(file)) {
r = PTR_ERR(file);
 \ /
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