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    Subject[PATCH v2 11/15] KVM: MMU: reintroduce kvm_mmu_isolate_page()
    Date
    It was removed by commit 834be0d83. Now we will need it to do lockless shadow
    page walking protected by rcu, so reintroduce it

    Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
    ---
    arch/x86/kvm/mmu.c | 23 ++++++++++++++++++++---
    1 file changed, 20 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index fe80019..2bf450a 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -1675,14 +1675,30 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
    percpu_counter_add(&kvm_total_used_mmu_pages, nr);
    }

    -static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
    +/*
    + * Remove the sp from shadow page cache, after call it,
    + * we can not find this sp from the cache, and the shadow
    + * page table is still valid.
    + *
    + * It should be under the protection of mmu lock.
    + */
    +static void kvm_mmu_isolate_page(struct kvm_mmu_page *sp)
    {
    ASSERT(is_empty_shadow_page(sp->spt));
    +
    hlist_del(&sp->hash_link);
    - list_del(&sp->link);
    - free_page((unsigned long)sp->spt);
    if (!sp->role.direct)
    free_page((unsigned long)sp->gfns);
    +}
    +
    +/*
    + * Free the shadow page table and the sp, we can do it
    + * out of the protection of mmu lock.
    + */
    +static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
    +{
    + list_del(&sp->link);
    + free_page((unsigned long)sp->spt);
    kmem_cache_free(mmu_page_header_cache, sp);
    }

    @@ -2361,6 +2377,7 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,

    list_for_each_entry_safe(sp, nsp, invalid_list, link) {
    WARN_ON(!sp->role.invalid || sp->root_count);
    + kvm_mmu_isolate_page(sp);
    kvm_mmu_free_page(sp);
    }
    }
    --
    1.8.1.4


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