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    SubjectRe: [PATCH v2 01/12] KVM: MMU: lazily drop large spte
    On 01/27/2013 08:06 PM, Gleb Natapov wrote:
    > On Wed, Jan 23, 2013 at 06:04:17PM +0800, Xiao Guangrong wrote:
    >> Do not drop large spte until it can be insteaded by small pages so that
    >> the guest can happliy read memory through it
    >>
    >> The idea is from Avi:
    >> | As I mentioned before, write-protecting a large spte is a good idea,
    >> | since it moves some work from protect-time to fault-time, so it reduces
    >> | jitter. This removes the need for the return value.
    >>
    >> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
    >> ---
    >> arch/x86/kvm/mmu.c | 21 ++++++---------------
    >> 1 files changed, 6 insertions(+), 15 deletions(-)
    >>
    >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    >> index 9f628f7..0f90269 100644
    >> --- a/arch/x86/kvm/mmu.c
    >> +++ b/arch/x86/kvm/mmu.c
    >> @@ -1105,7 +1105,7 @@ static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
    >>
    >> /*
    >> * Write-protect on the specified @sptep, @pt_protect indicates whether
    >> - * spte writ-protection is caused by protecting shadow page table.
    >> + * spte write-protection is caused by protecting shadow page table.
    >> * @flush indicates whether tlb need be flushed.
    >> *
    >> * Note: write protection is difference between drity logging and spte
    >> @@ -1114,31 +1114,23 @@ static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
    >> * its dirty bitmap is properly set.
    >> * - for spte protection, the spte can be writable only after unsync-ing
    >> * shadow page.
    >> - *
    >> - * Return true if the spte is dropped.
    >> */
    >> -static bool
    >> +static void
    >> spte_write_protect(struct kvm *kvm, u64 *sptep, bool *flush, bool pt_protect)
    > Since return value is not longer used make the function return true if flush is needed
    > instead of returning it via pointer to a variable.

    Right, i forgot to check it, will update it in the next version. Thanks for your pointing
    it out.




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