KVM: MMU: document write_flooding_count
Document write_flooding_count to Documentation/virtual/kvm/mmu.txt Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>hifive-unleashed-5.1
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@ -215,6 +215,15 @@ Shadow pages contain the following information:
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atomically. The reader uses this while running out of the MMU lock
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atomically. The reader uses this while running out of the MMU lock
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to detect in-progress updates and retry them until the writer has
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to detect in-progress updates and retry them until the writer has
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finished the write.
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finished the write.
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write_flooding_count:
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A guest may write to a page table many times, causing a lot of
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emulations if the page needs to be write-protected (see "Synchronized
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and unsynchronized pages" below). Leaf pages can be unsynchronized
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so that they do not trigger frequent emulation, but this is not
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possible for non-leafs. This field counts the number of emulations
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since the last time the page table was actually used; if emulation
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is triggered too frequently on this page, KVM will unmap the page
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to avoid emulation in the future.
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Reverse map
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Reverse map
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===========
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===========
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@ -233,6 +233,7 @@ struct kvm_mmu_page {
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int clear_spte_count;
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int clear_spte_count;
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#endif
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#endif
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/* Number of writes since the last time traversal visited this page. */
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int write_flooding_count;
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int write_flooding_count;
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};
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};
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