kvm: mmu: don't do memslot overflow check (13000523) · Commits · 戴 / test

As Andres pointed out: | I don't understand the value of this check here. Are we looking for a | broken memslot? Shouldn't this be a BUG_ON? Is this the place to care | about these things? npages is capped to KVM_MEM_MAX_NR_PAGES, i.e. | 2^31. A 64 bit overflow would be caused by a gigantic gfn_start which | would be trouble in many other ways. This patch drops the memslot overflow check to make the codes more simple. Reviewed-by:

Andres Lagar-Cavilla <andreslc@google.com> Signed-off-by:

Wanpeng Li <wanpeng.li@linux.intel.com> Message-Id: <1429064694-3072-1-git-send-email-wanpeng.li@linux.intel.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

+2 −10

Original line number	Diff line number	Diff line
		@@ -4504,19 +4504,12 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
		bool flush = false;
		unsigned long *rmapp;
		unsigned long last_index, index;
		gfn_t gfn_start, gfn_end;

		spin_lock(&kvm->mmu_lock);

		gfn_start = memslot->base_gfn;
		gfn_end = memslot->base_gfn + memslot->npages - 1;

		if (gfn_start >= gfn_end)
		goto out;

		rmapp = memslot->arch.rmap[0];
		last_index = gfn_to_index(gfn_end, memslot->base_gfn,
		PT_PAGE_TABLE_LEVEL);
		last_index = gfn_to_index(memslot->base_gfn + memslot->npages - 1,
		memslot->base_gfn, PT_PAGE_TABLE_LEVEL);

		for (index = 0; index <= last_index; ++index, ++rmapp) {
		if (*rmapp)
		@@ -4534,7 +4527,6 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
		if (flush)
		kvm_flush_remote_tlbs(kvm);

		out:
		spin_unlock(&kvm->mmu_lock);
		}

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