path: root/virt
diff options
authorSean Christopherson <sean.j.christopherson@intel.com>2019-02-05 12:54:17 -0800
committerPaolo Bonzini <pbonzini@redhat.com>2019-02-20 22:48:32 +0100
commit152482580a1b0accb60676063a1ac57b2d12daf6 (patch)
tree4c87b94da258dd28ff3e8da0c7efb5c8b6c5da68 /virt
parent4183683918efc3549b5ebddde4ed5edfdac45c17 (diff)
KVM: Call kvm_arch_memslots_updated() before updating memslots
kvm_arch_memslots_updated() is at this point in time an x86-specific hook for handling MMIO generation wraparound. x86 stashes 19 bits of the memslots generation number in its MMIO sptes in order to avoid full page fault walks for repeat faults on emulated MMIO addresses. Because only 19 bits are used, wrapping the MMIO generation number is possible, if unlikely. kvm_arch_memslots_updated() alerts x86 that the generation has changed so that it can invalidate all MMIO sptes in case the effective MMIO generation has wrapped so as to avoid using a stale spte, e.g. a (very) old spte that was created with generation==0. Given that the purpose of kvm_arch_memslots_updated() is to prevent consuming stale entries, it needs to be called before the new generation is propagated to memslots. Invalidating the MMIO sptes after updating memslots means that there is a window where a vCPU could dereference the new memslots generation, e.g. 0, and incorrectly reuse an old MMIO spte that was created with (pre-wrap) generation==0. Fixes: e59dbe09f8e6 ("KVM: Introduce kvm_arch_memslots_updated()") Cc: <stable@vger.kernel.org> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
2 files changed, 6 insertions, 3 deletions
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index fbdf3ac2f001..e0355e0f8712 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -2350,7 +2350,7 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
return 0;
-void kvm_arch_memslots_updated(struct kvm *kvm, struct kvm_memslots *slots)
+void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0a0ea8f4bb1b..d54f6578a849 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -874,6 +874,7 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
int as_id, struct kvm_memslots *slots)
struct kvm_memslots *old_memslots = __kvm_memslots(kvm, as_id);
+ u64 gen;
* Set the low bit in the generation, which disables SPTE caching
@@ -896,9 +897,11 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
* space 0 will use generations 0, 4, 8, ... while * address space 1 will
* use generations 2, 6, 10, 14, ...
- slots->generation += KVM_ADDRESS_SPACE_NUM * 2 - 1;
+ gen = slots->generation + KVM_ADDRESS_SPACE_NUM * 2 - 1;
- kvm_arch_memslots_updated(kvm, slots);
+ kvm_arch_memslots_updated(kvm, gen);
+ slots->generation = gen;
return old_memslots;