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Commit 116c14c0 authored by Alex Williamson's avatar Alex Williamson Committed by Gleb Natapov
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kvm: Fix memory slot generation updates 



Previous patch "kvm: Minor memory slot optimization" (b7f69c55)
overlooked the generation field of the memory slots.  Re-using the
original memory slots left us with with two slightly different memory
slots with the same generation.  To fix this, make update_memslots()
take a new parameter to specify the last generation.  This also makes
generation management more explicit to avoid such problems in the future.

Reported-by: default avatarTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent 871a069d

include/linux/kvm_host.h

+2 −1
Original line number Diff line number Diff line
@@ -428,7 +428,8 @@ void kvm_exit(void); 


void kvm_get_kvm(struct kvm *kvm);

void kvm_put_kvm(struct kvm *kvm);

void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new);

void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new,

		     u64 last_generation);



static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)

{

virt/kvm/kvm_main.c

+5 −4
Original line number Diff line number Diff line
@@ -672,7 +672,8 @@ static void sort_memslots(struct kvm_memslots *slots) 
		slots->id_to_index[slots->memslots[i].id] = i;

}



void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)

void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new,

		     u64 last_generation)

{

	if (new) {

		int id = new->id;
@@ -684,7 +685,7 @@ void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new) 
			sort_memslots(slots);

	}



	slots->generation++;

	slots->generation = last_generation + 1;

}



static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
@@ -819,7 +820,7 @@ int __kvm_set_memory_region(struct kvm *kvm, 
		slot = id_to_memslot(slots, mem->slot);

		slot->flags |= KVM_MEMSLOT_INVALID;



		update_memslots(slots, NULL);

		update_memslots(slots, NULL, kvm->memslots->generation);



		old_memslots = kvm->memslots;

		rcu_assign_pointer(kvm->memslots, slots);
@@ -867,7 +868,7 @@ int __kvm_set_memory_region(struct kvm *kvm, 
		memset(&new.arch, 0, sizeof(new.arch));

	}



	update_memslots(slots, &new);

	update_memslots(slots, &new, kvm->memslots->generation);

	old_memslots = kvm->memslots;

	rcu_assign_pointer(kvm->memslots, slots);

	synchronize_srcu_expedited(&kvm->srcu);