KVM: s390: pci: Hook to access KVM lowlevel from VFIO

We have a cross dependency between KVM and VFIO when using
s390 vfio_pci_zdev extensions for PCI passthrough
To be able to keep both subsystem modular we add a registering
hook inside the S390 core code.

This fixes a build problem when VFIO is built-in and KVM is built
as a module.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Fixes: 09340b2fca007 ("KVM: s390: pci: add routines to start/stop interpretive execution")
Cc: <stable@vger.kernel.org>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Link: https://lore.kernel.org/r/20220819122945.9309-1-pmorel@linux.ibm.com
Message-Id: <20220819122945.9309-1-pmorel@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index f39092e..b1e98a9 100644 (file)
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -1038,16 +1038,11 @@ static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
 #define __KVM_HAVE_ARCH_VM_FREE
 void kvm_arch_free_vm(struct kvm *kvm);
 
-#ifdef CONFIG_VFIO_PCI_ZDEV_KVM
-int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm);
-void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev);
-#else
-static inline int kvm_s390_pci_register_kvm(struct zpci_dev *dev,
-                                           struct kvm *kvm)
-{
-       return -EPERM;
-}
-static inline void kvm_s390_pci_unregister_kvm(struct zpci_dev *dev) {}
-#endif
+struct zpci_kvm_hook {
+       int (*kvm_register)(void *opaque, struct kvm *kvm);
+       void (*kvm_unregister)(void *opaque);
+};
+
+extern struct zpci_kvm_hook zpci_kvm_hook;
 
 #endif

diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index 4946fb7..bb8c335 100644 (file)
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -431,8 +431,9 @@ static void kvm_s390_pci_dev_release(struct zpci_dev *zdev)
  * available, enable them and let userspace indicate whether or not they will
  * be used (specify SHM bit to disable).
  */
-int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm)
+static int kvm_s390_pci_register_kvm(void *opaque, struct kvm *kvm)
 {
+       struct zpci_dev *zdev = opaque;
        int rc;
 
        if (!zdev)
@@ -510,10 +511,10 @@ err:
        kvm_put_kvm(kvm);
        return rc;
 }
-EXPORT_SYMBOL_GPL(kvm_s390_pci_register_kvm);
 
-void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev)
+static void kvm_s390_pci_unregister_kvm(void *opaque)
 {
+       struct zpci_dev *zdev = opaque;
        struct kvm *kvm;
 
        if (!zdev)
@@ -566,7 +567,6 @@ out:
 
        kvm_put_kvm(kvm);
 }
-EXPORT_SYMBOL_GPL(kvm_s390_pci_unregister_kvm);
 
 void kvm_s390_pci_init_list(struct kvm *kvm)
 {
@@ -678,6 +678,8 @@ int kvm_s390_pci_init(void)
 
        spin_lock_init(&aift->gait_lock);
        mutex_init(&aift->aift_lock);
+       zpci_kvm_hook.kvm_register = kvm_s390_pci_register_kvm;
+       zpci_kvm_hook.kvm_unregister = kvm_s390_pci_unregister_kvm;
 
        return 0;
 }
@@ -685,6 +687,8 @@ int kvm_s390_pci_init(void)
 void kvm_s390_pci_exit(void)
 {
        mutex_destroy(&aift->aift_lock);
+       zpci_kvm_hook.kvm_register = NULL;
+       zpci_kvm_hook.kvm_unregister = NULL;
 
        kfree(aift);
 }

diff --git a/arch/s390/pci/Makefile b/arch/s390/pci/Makefile
index bf557a1..5ae31ca 100644 (file)
--- a/arch/s390/pci/Makefile
+++ b/arch/s390/pci/Makefile
@@ -5,5 +5,5 @@
 
 obj-$(CONFIG_PCI)      += pci.o pci_irq.o pci_dma.o pci_clp.o pci_sysfs.o \
                           pci_event.o pci_debug.o pci_insn.o pci_mmio.o \
-                          pci_bus.o
+                          pci_bus.o pci_kvm_hook.o
 obj-$(CONFIG_PCI_IOV)  += pci_iov.o

diff --git a/arch/s390/pci/pci_kvm_hook.c b/arch/s390/pci/pci_kvm_hook.c
new file mode 100644 (file)
index 0000000..ff34baf
--- /dev/null
+++ b/arch/s390/pci/pci_kvm_hook.c
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VFIO ZPCI devices support
+ *
+ * Copyright (C) IBM Corp. 2022.  All rights reserved.
+ *     Author(s): Pierre Morel <pmorel@linux.ibm.com>
+ */
+#include <linux/kvm_host.h>
+
+struct zpci_kvm_hook zpci_kvm_hook;
+EXPORT_SYMBOL_GPL(zpci_kvm_hook);

diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
index e163aa9..0cbdcd1 100644 (file)
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -151,7 +151,10 @@ int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
        if (!vdev->vdev.kvm)
                return 0;
 
-       return kvm_s390_pci_register_kvm(zdev, vdev->vdev.kvm);
+       if (zpci_kvm_hook.kvm_register)
+               return zpci_kvm_hook.kvm_register(zdev, vdev->vdev.kvm);
+
+       return -ENOENT;
 }
 
 void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
@@ -161,5 +164,6 @@ void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
        if (!zdev || !vdev->vdev.kvm)
                return;
 
-       kvm_s390_pci_unregister_kvm(zdev);
+       if (zpci_kvm_hook.kvm_unregister)
+               zpci_kvm_hook.kvm_unregister(zdev);
 }