Document write_flooding_count to Documentation/virtual/kvm/mmu.txt Signed-off-by: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com> --- Documentation/virtual/kvm/mmu.txt | 8 ++++++++ arch/x86/include/asm/kvm_host.h | 5 +++++ 2 files changed, 13 insertions(+)
diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt index ce6df51..5a6b2e2 100644 --- a/Documentation/virtual/kvm/mmu.txt +++ b/Documentation/virtual/kvm/mmu.txt @@ -214,6 +214,14 @@ Shadow pages contain the following information: It is only used on 32bit host which helps us to detect whether updating the 64bit spte is complete so that we can avoid reading the truncated value out of mmu-lock. + write_flooding_count: + In order to sync the page table between guest and host, the page sometimes + needs to be write-protected (see "Synchronized and unsynchronized pages" + below), any write to the page can cause write emulation. If the emulation + on the page is too frequent we'd better unmap the page to avoid the + future emulation. write_flooding_count aims at this optimization which is + increased when the page needs to be write emulated and cleared when the + page is actually used. Reverse map =========== diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 1dac2c1..5eb5382 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -234,6 +234,11 @@ struct kvm_mmu_page { int clear_spte_count; #endif + /* + * Increased when the page needs to be write emulated, cleared + * when the page is actually used as page table to avoid frequent + * emulation on the page. + */ int write_flooding_count; }; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/