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[PATCH 02/12] KVM: MMU: check kvm_mmu_pages and mmu_page_path indices

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From: Xiao Guangrong <guangrong.xiao@linux.intel.com>

Give a special invalid index to the root of the walk, so that we
can check the consistency of kvm_mmu_pages and mmu_page_path.

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
[Extracted from a bigger patch proposed by Guangrong. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/mmu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4dee855897cf..3060873d8cab 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1840,6 +1840,8 @@ static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
 	return nr_unsync_leaf;
 }
 
+#define INVALID_INDEX (-1)
+
 static int mmu_unsync_walk(struct kvm_mmu_page *sp,
 			   struct kvm_mmu_pages *pvec)
 {
@@ -1847,7 +1849,7 @@ static int mmu_unsync_walk(struct kvm_mmu_page *sp,
 	if (!sp->unsync_children)
 		return 0;
 
-	mmu_pages_add(pvec, sp, 0);
+	mmu_pages_add(pvec, sp, INVALID_INDEX);
 	return __mmu_unsync_walk(sp, pvec);
 }
 
@@ -1996,6 +1998,8 @@ static int mmu_pages_first(struct kvm_mmu_pages *pvec,
 	if (pvec->nr == 0)
 		return 0;
 
+	WARN_ON(pvec->page[0].idx != INVALID_INDEX);
+
 	sp = pvec->page[0].sp;
 	level = sp->role.level;
 	WARN_ON(level == PT_PAGE_TABLE_LEVEL);
@@ -2020,6 +2024,7 @@ static void mmu_pages_clear_parents(struct mmu_page_path *parents)
 		if (!sp)
 			return;
 
+		WARN_ON(idx == INVALID_INDEX);
 		clear_unsync_child_bit(sp, idx);
 		level++;
 	} while (!sp->unsync_children);
-- 
1.8.3.1

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[PATCH 00/12] KVM: MMU: cleanup around kvm_sync_page, and a few micro-optimizations Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:20 +0100
  [PATCH 10/12] KVM: mark memory barrier with smp_mb__after_atomic Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:20 +0100
  [PATCH 05/12] KVM: MMU: use kvm_sync_page in kvm_sync_pages Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:30 +0100
  [PATCH 08/12] KVM: MMU: move zap/flush to kvm_mmu_get_page Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:30 +0100
    Re: [PATCH 08/12] KVM: MMU: move zap/flush to kvm_mmu_get_page Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-25 08:40 +0100
      Re: [PATCH 08/12] KVM: MMU: move zap/flush to kvm_mmu_get_page Paolo Bonzini <pbonzini@redhat.com> - 2016-02-25 09:50 +0100
  [PATCH 02/12] KVM: MMU: check kvm_mmu_pages and mmu_page_path indices Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:30 +0100
  [PATCH 03/12] KVM: MMU: introduce kvm_mmu_flush_or_zap Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:30 +0100
  [PATCH 04/12] KVM: MMU: move TLB flush out of __kvm_sync_page Paolo Bonzini <pbonzini@redhat.com> - 2016-02-24 14:30 +0100
  Re: [PATCH 00/12] KVM: MMU: cleanup around kvm_sync_page, and a few  micro-optimizations Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-25 09:30 +0100
    Re: [PATCH 00/12] KVM: MMU: cleanup around kvm_sync_page, and a few  micro-optimizations Paolo Bonzini <pbonzini@redhat.com> - 2016-02-25 09:50 +0100

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