diff mbox series

[v8,10/17] KVM: s390: pv: add mmu_notifier

Message ID 20220302181143.188283-11-imbrenda@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series KVM: s390: pv: implement lazy destroy for reboot | expand

Commit Message

Claudio Imbrenda March 2, 2022, 6:11 p.m. UTC
Add an mmu_notifier for protected VMs. The callback function is
triggered when the mm is torn down, and will attempt to convert all
protected vCPUs to non-protected. This allows the mm teardown to use
the destroy page UVC instead of export.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h |  2 ++
 arch/s390/kvm/kvm-s390.c         |  5 ++++-
 arch/s390/kvm/pv.c               | 26 ++++++++++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

Comments

kernel test robot March 3, 2022, 3:12 a.m. UTC | #1
Hi Claudio,

I love your patch! Yet something to improve:

[auto build test ERROR on kvm/master]
[also build test ERROR on v5.17-rc6 next-20220302]
[cannot apply to kvms390/next s390/features]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Claudio-Imbrenda/KVM-s390-pv-implement-lazy-destroy-for-reboot/20220303-021407
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
config: s390-buildonly-randconfig-r006-20220302 (https://download.01.org/0day-ci/archive/20220303/202203031051.SV8THyiU-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/bbf278ea47b7bdfb3c72e24faffedbb8a3a5b9f9
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Claudio-Imbrenda/KVM-s390-pv-implement-lazy-destroy-for-reboot/20220303-021407
        git checkout bbf278ea47b7bdfb3c72e24faffedbb8a3a5b9f9
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=s390 SHELL=/bin/bash arch/s390/kvm/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   arch/s390/kvm/kvm-s390.c: In function 'kvm_arch_destroy_vm':
>> arch/s390/kvm/kvm-s390.c:2839:17: error: implicit declaration of function 'mmu_notifier_unregister'; did you mean 'preempt_notifier_unregister'? [-Werror=implicit-function-declaration]
    2839 |                 mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~
         |                 preempt_notifier_unregister
   cc1: some warnings being treated as errors
--
   arch/s390/kvm/pv.c: In function 'kvm_s390_pv_init_vm':
>> arch/s390/kvm/pv.c:260:17: error: implicit declaration of function 'mmu_notifier_register'; did you mean 'mmu_notifier_release'? [-Werror=implicit-function-declaration]
     260 |                 mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
         |                 ^~~~~~~~~~~~~~~~~~~~~
         |                 mmu_notifier_release
   cc1: some warnings being treated as errors


vim +2839 arch/s390/kvm/kvm-s390.c

  2823	
  2824	void kvm_arch_destroy_vm(struct kvm *kvm)
  2825	{
  2826		u16 rc, rrc;
  2827	
  2828		kvm_destroy_vcpus(kvm);
  2829		sca_dispose(kvm);
  2830		kvm_s390_gisa_destroy(kvm);
  2831		/*
  2832		 * We are already at the end of life and kvm->lock is not taken.
  2833		 * This is ok as the file descriptor is closed by now and nobody
  2834		 * can mess with the pv state. To avoid lockdep_assert_held from
  2835		 * complaining we do not use kvm_s390_pv_is_protected.
  2836		 */
  2837		if (kvm_s390_pv_get_handle(kvm)) {
  2838			kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);
> 2839			mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
  2840		}
  2841		debug_unregister(kvm->arch.dbf);
  2842		free_page((unsigned long)kvm->arch.sie_page2);
  2843		if (!kvm_is_ucontrol(kvm))
  2844			gmap_remove(kvm->arch.gmap);
  2845		kvm_s390_destroy_adapters(kvm);
  2846		kvm_s390_clear_float_irqs(kvm);
  2847		kvm_s390_vsie_destroy(kvm);
  2848		KVM_EVENT(3, "vm 0x%pK destroyed", kvm);
  2849	}
  2850	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot March 3, 2022, 3:12 a.m. UTC | #2
Hi Claudio,

I love your patch! Yet something to improve:

[auto build test ERROR on kvm/master]
[also build test ERROR on v5.17-rc6 next-20220302]
[cannot apply to kvms390/next s390/features]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Claudio-Imbrenda/KVM-s390-pv-implement-lazy-destroy-for-reboot/20220303-021407
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
config: s390-randconfig-r001-20220302 (https://download.01.org/0day-ci/archive/20220303/202203031008.y7TlswqY-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project d271fc04d5b97b12e6b797c6067d3c96a8d7470e)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # https://github.com/0day-ci/linux/commit/bbf278ea47b7bdfb3c72e24faffedbb8a3a5b9f9
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Claudio-Imbrenda/KVM-s390-pv-implement-lazy-destroy-for-reboot/20220303-021407
        git checkout bbf278ea47b7bdfb3c72e24faffedbb8a3a5b9f9
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash arch/s390/kvm/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from arch/s390/kvm/kvm-s390.c:23:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:464:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:477:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
                                                             ^
   include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
   #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
                                                        ^
   In file included from arch/s390/kvm/kvm-s390.c:23:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
   #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
                                                        ^
   In file included from arch/s390/kvm/kvm-s390.c:23:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsb(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsw(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsl(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesb(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesw(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesl(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
>> arch/s390/kvm/kvm-s390.c:2839:3: error: implicit declaration of function 'mmu_notifier_unregister' [-Werror,-Wimplicit-function-declaration]
                   mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
                   ^
   arch/s390/kvm/kvm-s390.c:2839:3: note: did you mean 'preempt_notifier_unregister'?
   include/linux/preempt.h:346:6: note: 'preempt_notifier_unregister' declared here
   void preempt_notifier_unregister(struct preempt_notifier *notifier);
        ^
   12 warnings and 1 error generated.
--
   In file included from arch/s390/kvm/pv.c:9:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:464:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:477:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
                                                             ^
   include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
   #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
                                                        ^
   In file included from arch/s390/kvm/pv.c:9:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
   #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
                                                        ^
   In file included from arch/s390/kvm/pv.c:9:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsb(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsw(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsl(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesb(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesw(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesl(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
>> arch/s390/kvm/pv.c:260:3: error: implicit declaration of function 'mmu_notifier_register' [-Werror,-Wimplicit-function-declaration]
                   mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
                   ^
   arch/s390/kvm/pv.c:260:3: note: did you mean 'mmu_notifier_release'?
   include/linux/mmu_notifier.h:679:20: note: 'mmu_notifier_release' declared here
   static inline void mmu_notifier_release(struct mm_struct *mm)
                      ^
   12 warnings and 1 error generated.


vim +/mmu_notifier_unregister +2839 arch/s390/kvm/kvm-s390.c

  2823	
  2824	void kvm_arch_destroy_vm(struct kvm *kvm)
  2825	{
  2826		u16 rc, rrc;
  2827	
  2828		kvm_destroy_vcpus(kvm);
  2829		sca_dispose(kvm);
  2830		kvm_s390_gisa_destroy(kvm);
  2831		/*
  2832		 * We are already at the end of life and kvm->lock is not taken.
  2833		 * This is ok as the file descriptor is closed by now and nobody
  2834		 * can mess with the pv state. To avoid lockdep_assert_held from
  2835		 * complaining we do not use kvm_s390_pv_is_protected.
  2836		 */
  2837		if (kvm_s390_pv_get_handle(kvm)) {
  2838			kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);
> 2839			mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
  2840		}
  2841		debug_unregister(kvm->arch.dbf);
  2842		free_page((unsigned long)kvm->arch.sie_page2);
  2843		if (!kvm_is_ucontrol(kvm))
  2844			gmap_remove(kvm->arch.gmap);
  2845		kvm_s390_destroy_adapters(kvm);
  2846		kvm_s390_clear_float_irqs(kvm);
  2847		kvm_s390_vsie_destroy(kvm);
  2848		KVM_EVENT(3, "vm 0x%pK destroyed", kvm);
  2849	}
  2850	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index a22c9266ea05..1bccb8561ba9 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -19,6 +19,7 @@ 
 #include <linux/kvm.h>
 #include <linux/seqlock.h>
 #include <linux/module.h>
+#include <linux/mmu_notifier.h>
 #include <asm/debug.h>
 #include <asm/cpu.h>
 #include <asm/fpu/api.h>
@@ -921,6 +922,7 @@  struct kvm_s390_pv {
 	u64 guest_len;
 	unsigned long stor_base;
 	void *stor_var;
+	struct mmu_notifier mmu_notifier;
 };
 
 struct kvm_arch{
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 21fcca09e9bf..446f89db93a1 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -32,6 +32,7 @@ 
 #include <linux/sched/signal.h>
 #include <linux/string.h>
 #include <linux/pgtable.h>
+#include <linux/mmu_notifier.h>
 
 #include <asm/asm-offsets.h>
 #include <asm/lowcore.h>
@@ -2833,8 +2834,10 @@  void kvm_arch_destroy_vm(struct kvm *kvm)
 	 * can mess with the pv state. To avoid lockdep_assert_held from
 	 * complaining we do not use kvm_s390_pv_is_protected.
 	 */
-	if (kvm_s390_pv_get_handle(kvm))
+	if (kvm_s390_pv_get_handle(kvm)) {
 		kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);
+		mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
+	}
 	debug_unregister(kvm->arch.dbf);
 	free_page((unsigned long)kvm->arch.sie_page2);
 	if (!kvm_is_ucontrol(kvm))
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 76ef33a277d3..788b96b36931 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -14,6 +14,7 @@ 
 #include <asm/mman.h>
 #include <linux/pagewalk.h>
 #include <linux/sched/mm.h>
+#include <linux/mmu_notifier.h>
 #include "kvm-s390.h"
 
 static void kvm_s390_clear_pv_state(struct kvm *kvm)
@@ -192,6 +193,26 @@  int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	return -EIO;
 }
 
+static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
+					     struct mm_struct *mm)
+{
+	struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
+	u16 dummy;
+
+	/*
+	 * No locking is needed since this is the last thread of the last user of this
+	 * struct mm.
+	 * When the struct kvm gets deinitialized, this notifier is also
+	 * unregistered. This means that if this notifier runs, then the
+	 * struct kvm is still valid.
+	 */
+	kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+}
+
+static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {
+	.release = kvm_s390_pv_mmu_notifier_release,
+};
+
 int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	struct uv_cb_cgc uvcb = {
@@ -233,6 +254,11 @@  int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 		return -EIO;
 	}
 	kvm->arch.gmap->guest_handle = uvcb.guest_handle;
+	/* Add the notifier only once. No races because we hold kvm->lock */
+	if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) {
+		kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops;
+		mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
+	}
 	return 0;
 }