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authorBen Gardon <bgardon@google.com>2019-03-12 18:45:58 (GMT)
committerPaolo Bonzini <pbonzini@redhat.com>2019-03-15 18:16:45 (GMT)
commit92da008fa21034c369cdb8ca2b629fe5c196826b (patch)
tree780a56475b588838e148a1c198b6a67b379abd46
parent71783e09b4874c845819b5658b968d8b5b899333 (diff)
Revert "KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()"
This reverts commit 71883a62fcd6c70639fa12cda733378b4d997409. The above commit contains an optimization to kvm_zap_gfn_range which uses gfn-limited TLB flushes, if enabled. If using these limited flushes, kvm_zap_gfn_range passes lock_flush_tlb=false to slot_handle_level_range which creates a race when the function unlocks to call cond_resched. See an example of this race below: CPU 0 CPU 1 CPU 3 // zap_direct_gfn_range mmu_lock() // *ptep == pte_1 *ptep = 0 if (lock_flush_tlb) flush_tlbs() mmu_unlock() // In invalidate range // MMU notifier mmu_lock() if (pte != 0) *ptep = 0 flush = true if (flush) flush_remote_tlbs() mmu_unlock() return // Host MM reallocates // page previously // backing guest memory. // Guest accesses // invalid page // through pte_1 // in its TLB!! Tested: Ran all kvm-unit-tests on a Intel Haswell machine with and without this patch. The patch introduced no new failures. Signed-off-by: Ben Gardon <bgardon@google.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/mmu.c16
1 files changed, 3 insertions, 13 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 8d43b7c..4cda5ee 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5660,13 +5660,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
struct kvm_memslots *slots;
struct kvm_memory_slot *memslot;
- bool flush_tlb = true;
- bool flush = false;
int i;
- if (kvm_available_flush_tlb_with_range())
- flush_tlb = false;
-
spin_lock(&kvm->mmu_lock);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
slots = __kvm_memslots(kvm, i);
@@ -5678,17 +5673,12 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
if (start >= end)
continue;
- flush |= slot_handle_level_range(kvm, memslot,
- kvm_zap_rmapp, PT_PAGE_TABLE_LEVEL,
- PT_MAX_HUGEPAGE_LEVEL, start,
- end - 1, flush_tlb);
+ slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
+ PT_PAGE_TABLE_LEVEL, PT_MAX_HUGEPAGE_LEVEL,
+ start, end - 1, true);
}
}
- if (flush)
- kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
- gfn_end - gfn_start + 1);
-
spin_unlock(&kvm->mmu_lock);
}

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