On Thu, Sep 05, 2013 at 06:29:08PM +0800, Xiao Guangrong wrote:
> Now we can flush all the TLBs out of the mmu lock without TLB corruption when
> write-proect the sptes, it is because:
> - we have marked large sptes readonly instead of dropping them that means we
> just change the spte from writable to readonly so that we only need to care
> the case of changing spte from present to present (changing the spte from
> present to nonpresent will flush all the TLBs immediately), in other words,
> the only case we need to care is mmu_spte_update()
>
> - in mmu_spte_update(), we have checked
> SPTE_HOST_WRITEABLE | PTE_MMU_WRITEABLE instead of PT_WRITABLE_MASK, that
> means it does not depend on PT_WRITABLE_MASK anymore
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 18 ++++++++++++++----
> arch/x86/kvm/x86.c | 9 +++++++--
> 2 files changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 7488229..a983570 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4320,15 +4320,25 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
> if (*rmapp)
> __rmap_write_protect(kvm, rmapp, false);
>
> - if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
> - kvm_flush_remote_tlbs(kvm);
> + if (need_resched() || spin_needbreak(&kvm->mmu_lock))
> cond_resched_lock(&kvm->mmu_lock);
> - }
> }
> }
>
> - kvm_flush_remote_tlbs(kvm);
> spin_unlock(&kvm->mmu_lock);
> +
> + /*
> + * We can flush all the TLBs out of the mmu lock without TLB
> + * corruption since we just change the spte from writable to
> + * readonly so that we only need to care the case of changing
> + * spte from present to present (changing the spte from present
> + * to nonpresent will flush all the TLBs immediately), in other
> + * words, the only case we care is mmu_spte_update() where we
> + * haved checked SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE
> + * instead of PT_WRITABLE_MASK, that means it does not depend
> + * on PT_WRITABLE_MASK anymore.
> + */
> + kvm_flush_remote_tlbs(kvm);
> }
What about need_remote_flush?
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