KVM: MIPS: Hardcode callbacks to hardware virtualization extensions

Now that KVM no longer supports trap-and-emulate (see commit 45c7e8af4a5e
"MIPS: Remove KVM_TE support"), hardcode the MIPS callbacks to the
virtualization callbacks.

Harcoding the callbacks eliminates the technically-unnecessary check on
non-NULL kvm_mips_callbacks in kvm_arch_init().  MIPS has never supported
multiple in-tree modules, i.e. barring an out-of-tree module, where
copying and renaming kvm.ko counts as "out-of-tree", KVM could never
encounter a non-NULL set of callbacks during module init.

The callback check is also subtly broken, as it is not thread safe,
i.e. if there were multiple modules, loading both concurrently would
create a race between checking and setting kvm_mips_callbacks.

Given that out-of-tree shenanigans are not the kernel's responsibility,
hardcode the callbacks to simplify the code.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20221130230934.1014142-22-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

4 files changed, 7 insertions, 25 deletions

diff --git a/arch/mips/kvm/Makefile b/arch/mips/kvm/Makefile
index 21ff75bcdbc4..805aeea2166e 100644
--- a/arch/mips/kvm/Makefile
+++ b/arch/mips/kvm/Makefile
@@ -17,4 +17,4 @@ kvm-$(CONFIG_CPU_LOONGSON64) += loongson_ipi.o
 
 kvm-y		+= vz.o
 obj-$(CONFIG_KVM)	+= kvm.o
-obj-y			+= callback.o tlb.o
+obj-y			+= tlb.o
diff --git a/arch/mips/kvm/callback.c b/arch/mips/kvm/callback.c
deleted file mode 100644
index d88aa2173fb0..000000000000
--- a/arch/mips/kvm/callback.c
+++ /dev/null
@@ -1,14 +0,0 @@
-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
- * Authors: Yann Le Du <ledu@kymasys.com>
- */
-
-#include <linux/export.h>
-#include <linux/kvm_host.h>
-
-struct kvm_mips_callbacks *kvm_mips_callbacks;
-EXPORT_SYMBOL_GPL(kvm_mips_callbacks);
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index af29490d9740..f0a6c245d1ff 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1012,17 +1012,12 @@ long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 
 int kvm_arch_init(void *opaque)
 {
-	if (kvm_mips_callbacks) {
-		kvm_err("kvm: module already exists\n");
-		return -EEXIST;
-	}
-
-	return kvm_mips_emulation_init(&kvm_mips_callbacks);
+	return kvm_mips_emulation_init();
 }
 
 void kvm_arch_exit(void)
 {
-	kvm_mips_callbacks = NULL;
+
 }
 
 int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu,
diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c
index c706f5890a05..dafab003ea0d 100644
--- a/arch/mips/kvm/vz.c
+++ b/arch/mips/kvm/vz.c
@@ -3304,7 +3304,10 @@ static struct kvm_mips_callbacks kvm_vz_callbacks = {
 	.vcpu_reenter = kvm_vz_vcpu_reenter,
 };
 
-int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks)
+/* FIXME: Get rid of the callbacks now that trap-and-emulate is gone. */
+struct kvm_mips_callbacks *kvm_mips_callbacks = &kvm_vz_callbacks;
+
+int kvm_mips_emulation_init(void)
 {
 	if (!cpu_has_vz)
 		return -ENODEV;
@@ -3318,7 +3321,5 @@ int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks)
 		return -ENODEV;
 
 	pr_info("Starting KVM with MIPS VZ extensions\n");
-
-	*install_callbacks = &kvm_vz_callbacks;
 	return 0;
 }