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KVM: Drop .on_unlock() mmu_notifier hook

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Drop the .on_unlock() mmu_notifer hook now that it's no longer used for
notifying arch code that memory has been reclaimed.  Adding .on_unlock()
and invoking it *after* dropping mmu_lock was a terrible idea, as doing so
resulted in .on_lock() and .on_unlock() having divergent and asymmetric
behavior, and set future developers up for failure, i.e. all but asked for
bugs where KVM relied on using .on_unlock() to try to run a callback while
holding mmu_lock.

Opportunistically add a lockdep assertion in kvm_mmu_invalidate_end() to
guard against future bugs of this nature.

Reported-by: Isaku Yamahata <isaku.yamahata@intel.com>
Link: https://lore.kernel.org/all/20230802203119.GB2021422@ls.amr.corp.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Message-Id: <20231027182217.3615211-12-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-10-27 11:21:53 -07:00 • committed by Paolo Bonzini
parent cec29eef0a
commit 193bbfaacc
1 changed files with 1 additions and 10 deletions
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11
virt/kvm/kvm_main.c
View file

@ -544,7 +544,6 @@ static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
typedef bool (*gfn_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range); typedef bool (*gfn_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range);
typedef void (*on_lock_fn_t)(struct kvm *kvm); typedef void (*on_lock_fn_t)(struct kvm *kvm);
typedef void (*on_unlock_fn_t)(struct kvm *kvm);
struct kvm_mmu_notifier_range { struct kvm_mmu_notifier_range {
/* /*
@ -556,7 +555,6 @@ struct kvm_mmu_notifier_range {
union kvm_mmu_notifier_arg arg; union kvm_mmu_notifier_arg arg;
gfn_handler_t handler; gfn_handler_t handler;
on_lock_fn_t on_lock; on_lock_fn_t on_lock;
on_unlock_fn_t on_unlock;
bool flush_on_ret; bool flush_on_ret;
bool may_block; bool may_block;
}; };
@ -663,11 +661,8 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
if (range->flush_on_ret && r.ret) if (range->flush_on_ret && r.ret)
kvm_flush_remote_tlbs(kvm); kvm_flush_remote_tlbs(kvm);
if (r.found_memslot) { if (r.found_memslot)
KVM_MMU_UNLOCK(kvm); KVM_MMU_UNLOCK(kvm);
if (!IS_KVM_NULL_FN(range->on_unlock))
range->on_unlock(kvm);
}
srcu_read_unlock(&kvm->srcu, idx); srcu_read_unlock(&kvm->srcu, idx);
@ -687,7 +682,6 @@ static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
.arg = arg, .arg = arg,
.handler = handler, .handler = handler,
.on_lock = (void *)kvm_null_fn, .on_lock = (void *)kvm_null_fn,
.on_unlock = (void *)kvm_null_fn,
.flush_on_ret = true, .flush_on_ret = true,
.may_block = false, .may_block = false,
}; };
@ -706,7 +700,6 @@ static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn
.end = end, .end = end,
.handler = handler, .handler = handler,
.on_lock = (void *)kvm_null_fn, .on_lock = (void *)kvm_null_fn,
.on_unlock = (void *)kvm_null_fn,
.flush_on_ret = false, .flush_on_ret = false,
.may_block = false, .may_block = false,
}; };
@ -813,7 +806,6 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
.end = range->end, .end = range->end,
.handler = kvm_mmu_unmap_gfn_range, .handler = kvm_mmu_unmap_gfn_range,
.on_lock = kvm_mmu_invalidate_begin, .on_lock = kvm_mmu_invalidate_begin,
.on_unlock = (void *)kvm_null_fn,
.flush_on_ret = true, .flush_on_ret = true,
.may_block = mmu_notifier_range_blockable(range), .may_block = mmu_notifier_range_blockable(range),
}; };
@ -891,7 +883,6 @@ static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
.end = range->end, .end = range->end,
.handler = (void *)kvm_null_fn, .handler = (void *)kvm_null_fn,
.on_lock = kvm_mmu_invalidate_end, .on_lock = kvm_mmu_invalidate_end,
.on_unlock = (void *)kvm_null_fn,
.flush_on_ret = false, .flush_on_ret = false,
.may_block = mmu_notifier_range_blockable(range), .may_block = mmu_notifier_range_blockable(range),
}; };