* [PATCH 1/2] KVM: remove CONFIG_KVM_GENERIC_MMU_NOTIFIER
2026-02-12 10:52 [PATCH 0/2] KVM: require generic MMU notifier implementation Paolo Bonzini
@ 2026-02-12 10:52 ` Paolo Bonzini
2026-02-12 17:16 ` kernel test robot
` (2 more replies)
2026-02-12 10:52 ` [PATCH 2/2] KVM: always define KVM_CAP_SYNC_MMU Paolo Bonzini
1 sibling, 3 replies; 6+ messages in thread
From: Paolo Bonzini @ 2026-02-12 10:52 UTC (permalink / raw)
To: linux-kernel, kvm
All architectures now use MMU notifier for KVM page table management.
Remove the Kconfig symbol and the code that is used when it is
disabled.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/arm64/kvm/Kconfig | 1 -
arch/loongarch/kvm/Kconfig | 1 -
arch/mips/kvm/Kconfig | 1 -
arch/powerpc/kvm/Kconfig | 4 ----
arch/powerpc/kvm/powerpc.c | 1 -
arch/riscv/kvm/Kconfig | 1 -
arch/s390/kvm/Kconfig | 1 -
arch/x86/kvm/Kconfig | 1 -
include/linux/kvm_host.h | 7 +------
virt/kvm/Kconfig | 8 --------
virt/kvm/kvm_main.c | 16 ----------------
11 files changed, 1 insertion(+), 41 deletions(-)
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 4f803fd1c99a..7d1f22fd490b 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -21,7 +21,6 @@ menuconfig KVM
bool "Kernel-based Virtual Machine (KVM) support"
select KVM_COMMON
select KVM_GENERIC_HARDWARE_ENABLING
- select KVM_GENERIC_MMU_NOTIFIER
select HAVE_KVM_CPU_RELAX_INTERCEPT
select KVM_MMIO
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
index ed4f724db774..8e5213609975 100644
--- a/arch/loongarch/kvm/Kconfig
+++ b/arch/loongarch/kvm/Kconfig
@@ -28,7 +28,6 @@ config KVM
select KVM_COMMON
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_GENERIC_HARDWARE_ENABLING
- select KVM_GENERIC_MMU_NOTIFIER
select KVM_MMIO
select VIRT_XFER_TO_GUEST_WORK
select SCHED_INFO
diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
index cc13cc35f208..b1b9a1d67758 100644
--- a/arch/mips/kvm/Kconfig
+++ b/arch/mips/kvm/Kconfig
@@ -23,7 +23,6 @@ config KVM
select KVM_COMMON
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_MMIO
- select KVM_GENERIC_MMU_NOTIFIER
select KVM_GENERIC_HARDWARE_ENABLING
select HAVE_KVM_READONLY_MEM
help
diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index c9a2d50ff1b0..9a0d1c1aca6c 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -38,7 +38,6 @@ config KVM_BOOK3S_64_HANDLER
config KVM_BOOK3S_PR_POSSIBLE
bool
select KVM_MMIO
- select KVM_GENERIC_MMU_NOTIFIER
config KVM_BOOK3S_HV_POSSIBLE
bool
@@ -81,7 +80,6 @@ config KVM_BOOK3S_64_HV
tristate "KVM for POWER7 and later using hypervisor mode in host"
depends on KVM_BOOK3S_64 && PPC_POWERNV
select KVM_BOOK3S_HV_POSSIBLE
- select KVM_GENERIC_MMU_NOTIFIER
select KVM_BOOK3S_HV_PMU
select CMA
help
@@ -203,7 +201,6 @@ config KVM_E500V2
depends on !CONTEXT_TRACKING_USER
select KVM
select KVM_MMIO
- select KVM_GENERIC_MMU_NOTIFIER
help
Support running unmodified E500 guest kernels in virtual machines on
E500v2 host processors.
@@ -220,7 +217,6 @@ config KVM_E500MC
select KVM
select KVM_MMIO
select KVM_BOOKE_HV
- select KVM_GENERIC_MMU_NOTIFIER
help
Support running unmodified E500MC/E5500/E6500 guest kernels in
virtual machines on E500MC/E5500/E6500 host processors.
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 9a89a6d98f97..3da40ea8c562 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -625,7 +625,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
break;
#endif
case KVM_CAP_SYNC_MMU:
- BUILD_BUG_ON(!IS_ENABLED(CONFIG_KVM_GENERIC_MMU_NOTIFIER));
r = 1;
break;
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index 77379f77840a..ec2cee0a39e0 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -30,7 +30,6 @@ config KVM
select KVM_GENERIC_HARDWARE_ENABLING
select KVM_MMIO
select VIRT_XFER_TO_GUEST_WORK
- select KVM_GENERIC_MMU_NOTIFIER
select SCHED_INFO
select GUEST_PERF_EVENTS if PERF_EVENTS
help
diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
index 917ac740513e..7f2c966e70af 100644
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -30,7 +30,6 @@ config KVM
select KVM_VFIO
select MMU_NOTIFIER
select VIRT_XFER_TO_GUEST_WORK
- select KVM_GENERIC_MMU_NOTIFIER
select KVM_MMU_LOCKLESS_AGING
help
Support hosting paravirtualized guest machines using the SIE
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index d916bd766c94..801bf9e520db 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -20,7 +20,6 @@ if VIRTUALIZATION
config KVM_X86
def_tristate KVM if (KVM_INTEL != n || KVM_AMD != n)
select KVM_COMMON
- select KVM_GENERIC_MMU_NOTIFIER
select KVM_ELIDE_TLB_FLUSH_IF_YOUNG
select KVM_MMU_LOCKLESS_AGING
select HAVE_KVM_IRQCHIP
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d42a95cbcfbc..db9b6856f6cb 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -253,7 +253,6 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
#endif
-#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
union kvm_mmu_notifier_arg {
unsigned long attributes;
};
@@ -275,7 +274,6 @@ struct kvm_gfn_range {
bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
-#endif
enum {
OUTSIDE_GUEST_MODE,
@@ -849,13 +847,12 @@ struct kvm {
struct hlist_head irq_ack_notifier_list;
#endif
-#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
struct mmu_notifier mmu_notifier;
unsigned long mmu_invalidate_seq;
long mmu_invalidate_in_progress;
gfn_t mmu_invalidate_range_start;
gfn_t mmu_invalidate_range_end;
-#endif
+
struct list_head devices;
u64 manual_dirty_log_protect;
struct dentry *debugfs_dentry;
@@ -2118,7 +2115,6 @@ extern const struct _kvm_stats_desc kvm_vm_stats_desc[];
extern const struct kvm_stats_header kvm_vcpu_stats_header;
extern const struct _kvm_stats_desc kvm_vcpu_stats_desc[];
-#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
static inline int mmu_invalidate_retry(struct kvm *kvm, unsigned long mmu_seq)
{
if (unlikely(kvm->mmu_invalidate_in_progress))
@@ -2196,7 +2192,6 @@ static inline bool mmu_invalidate_retry_gfn_unsafe(struct kvm *kvm,
return READ_ONCE(kvm->mmu_invalidate_seq) != mmu_seq;
}
-#endif
#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 267c7369c765..9e7d3553e6a7 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -93,24 +93,16 @@ config HAVE_KVM_PM_NOTIFIER
config KVM_GENERIC_HARDWARE_ENABLING
bool
-config KVM_GENERIC_MMU_NOTIFIER
- select MMU_NOTIFIER
- bool
-
config KVM_ELIDE_TLB_FLUSH_IF_YOUNG
- depends on KVM_GENERIC_MMU_NOTIFIER
bool
config KVM_MMU_LOCKLESS_AGING
- depends on KVM_GENERIC_MMU_NOTIFIER
bool
config KVM_GENERIC_MEMORY_ATTRIBUTES
- depends on KVM_GENERIC_MMU_NOTIFIER
bool
config KVM_GUEST_MEMFD
- depends on KVM_GENERIC_MMU_NOTIFIER
select XARRAY_MULTI
bool
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 61dca8d37abc..bf5606d76f0c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -502,7 +502,6 @@ void kvm_destroy_vcpus(struct kvm *kvm)
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_destroy_vcpus);
-#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
{
return container_of(mn, struct kvm, mmu_notifier);
@@ -901,15 +900,6 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
}
-#else /* !CONFIG_KVM_GENERIC_MMU_NOTIFIER */
-
-static int kvm_init_mmu_notifier(struct kvm *kvm)
-{
- return 0;
-}
-
-#endif /* CONFIG_KVM_GENERIC_MMU_NOTIFIER */
-
#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
static int kvm_pm_notifier_call(struct notifier_block *bl,
unsigned long state,
@@ -1226,10 +1216,8 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
out_err_no_debugfs:
kvm_coalesced_mmio_free(kvm);
out_no_coalesced_mmio:
-#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
if (kvm->mmu_notifier.ops)
mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
-#endif
out_err_no_mmu_notifier:
kvm_disable_virtualization();
out_err_no_disable:
@@ -1292,7 +1280,6 @@ static void kvm_destroy_vm(struct kvm *kvm)
kvm->buses[i] = NULL;
}
kvm_coalesced_mmio_free(kvm);
-#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
/*
* At this point, pending calls to invalidate_range_start()
@@ -1311,9 +1298,6 @@ static void kvm_destroy_vm(struct kvm *kvm)
kvm->mn_active_invalidate_count = 0;
else
WARN_ON(kvm->mmu_invalidate_in_progress);
-#else
- kvm_flush_shadow_all(kvm);
-#endif
kvm_arch_destroy_vm(kvm);
kvm_destroy_devices(kvm);
for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
--
2.52.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 2/2] KVM: always define KVM_CAP_SYNC_MMU
2026-02-12 10:52 [PATCH 0/2] KVM: require generic MMU notifier implementation Paolo Bonzini
2026-02-12 10:52 ` [PATCH 1/2] KVM: remove CONFIG_KVM_GENERIC_MMU_NOTIFIER Paolo Bonzini
@ 2026-02-12 10:52 ` Paolo Bonzini
1 sibling, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2026-02-12 10:52 UTC (permalink / raw)
To: linux-kernel, kvm
KVM_CAP_SYNC_MMU is provided by KVM's MMU notifiers, which are now always
available. Move the definition from individual architectures to common
code.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
Documentation/virt/kvm/api.rst | 10 ++++------
arch/arm64/kvm/arm.c | 1 -
arch/loongarch/kvm/vm.c | 1 -
arch/mips/kvm/mips.c | 1 -
arch/powerpc/kvm/powerpc.c | 5 -----
arch/riscv/kvm/vm.c | 1 -
arch/s390/kvm/kvm-s390.c | 1 -
arch/x86/kvm/x86.c | 1 -
virt/kvm/kvm_main.c | 1 +
9 files changed, 5 insertions(+), 17 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index fc5736839edd..6f85e1b321dd 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1396,7 +1396,10 @@ or its flags may be modified, but it may not be resized.
Memory for the region is taken starting at the address denoted by the
field userspace_addr, which must point at user addressable memory for
the entire memory slot size. Any object may back this memory, including
-anonymous memory, ordinary files, and hugetlbfs.
+anonymous memory, ordinary files, and hugetlbfs. Changes in the backing
+of the memory region are automatically reflected into the guest.
+For example, an mmap() that affects the region will be made visible
+immediately. Another example is madvise(MADV_DROP).
On architectures that support a form of address tagging, userspace_addr must
be an untagged address.
@@ -1412,11 +1415,6 @@ use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
to make a new slot read-only. In this case, writes to this memory will be
posted to userspace as KVM_EXIT_MMIO exits.
-When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
-the memory region are automatically reflected into the guest. For example, an
-mmap() that affects the region will be made visible immediately. Another
-example is madvise(MADV_DROP).
-
For TDX guest, deleting/moving memory region loses guest memory contents.
Read only region isn't supported. Only as-id 0 is supported.
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 94d5b0b99fd1..7309f5084388 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -358,7 +358,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
break;
case KVM_CAP_IOEVENTFD:
case KVM_CAP_USER_MEMORY:
- case KVM_CAP_SYNC_MMU:
case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
case KVM_CAP_ONE_REG:
case KVM_CAP_ARM_PSCI:
diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
index 9681ade890c6..41b58ec45f41 100644
--- a/arch/loongarch/kvm/vm.c
+++ b/arch/loongarch/kvm/vm.c
@@ -117,7 +117,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_ONE_REG:
case KVM_CAP_ENABLE_CAP:
case KVM_CAP_READONLY_MEM:
- case KVM_CAP_SYNC_MMU:
case KVM_CAP_IMMEDIATE_EXIT:
case KVM_CAP_IOEVENTFD:
case KVM_CAP_MP_STATE:
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index b0fb92fda4d4..29d9f630edfb 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1035,7 +1035,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_ONE_REG:
case KVM_CAP_ENABLE_CAP:
case KVM_CAP_READONLY_MEM:
- case KVM_CAP_SYNC_MMU:
case KVM_CAP_IMMEDIATE_EXIT:
r = 1;
break;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 3da40ea8c562..00302399fc37 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -623,11 +623,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = !!(hv_enabled && kvmppc_hv_ops->enable_nested &&
!kvmppc_hv_ops->enable_nested(NULL));
break;
-#endif
- case KVM_CAP_SYNC_MMU:
- r = 1;
- break;
-#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
case KVM_CAP_PPC_HTAB_FD:
r = hv_enabled;
break;
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 66d91ae6e9b2..b4afef7e59fc 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -181,7 +181,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
break;
case KVM_CAP_IOEVENTFD:
case KVM_CAP_USER_MEMORY:
- case KVM_CAP_SYNC_MMU:
case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
case KVM_CAP_ONE_REG:
case KVM_CAP_READONLY_MEM:
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index de645025db0f..6591ee56bf5b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -601,7 +601,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
switch (ext) {
case KVM_CAP_S390_PSW:
case KVM_CAP_S390_GMAP:
- case KVM_CAP_SYNC_MMU:
#ifdef CONFIG_KVM_S390_UCONTROL
case KVM_CAP_S390_UCONTROL:
#endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 391f4a5ce6dd..ac31b098bfbd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4805,7 +4805,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
#endif
case KVM_CAP_NOP_IO_DELAY:
case KVM_CAP_MP_STATE:
- case KVM_CAP_SYNC_MMU:
case KVM_CAP_USER_NMI:
case KVM_CAP_IRQ_INJECT_STATUS:
case KVM_CAP_IOEVENTFD:
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bf5606d76f0c..51d1f7d4905e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4870,6 +4870,7 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
{
switch (arg) {
+ case KVM_CAP_SYNC_MMU:
case KVM_CAP_USER_MEMORY:
case KVM_CAP_USER_MEMORY2:
case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
--
2.52.0
^ permalink raw reply related [flat|nested] 6+ messages in thread