lkml.org 
[lkml]   [2015]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 06/10] KVM: x86: MMU: Consolidate BUG_ON checks for reverse-mapped sptes
    At some call sites of rmap_get_first() and rmap_get_next(), BUG_ON is
    placed right after the call to detect unrelated sptes which must not be
    found in the reverse-mapping list.

    Move this check in rmap_get_first/next() so that all call sites, not
    just the users of the for_each_rmap_spte() macro, will be checked the
    same way.

    One thing to keep in mind is that kvm_mmu_unlink_parents() also uses
    rmap_get_first() to handle parent sptes. The change will not break it
    because parent sptes are present, at least until drop_parent_pte()
    actually unlinks them, and not mmio-sptes.

    Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
    ---
    Documentation/virtual/kvm/mmu.txt | 4 ++--
    arch/x86/kvm/mmu.c | 26 +++++++++++++++++---------
    2 files changed, 19 insertions(+), 11 deletions(-)

    diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
    index 3a4d681..daf9c0f 100644
    --- a/Documentation/virtual/kvm/mmu.txt
    +++ b/Documentation/virtual/kvm/mmu.txt
    @@ -203,10 +203,10 @@ Shadow pages contain the following information:
    page cannot be destroyed. See role.invalid.
    parent_ptes:
    The reverse mapping for the pte/ptes pointing at this page's spt. If
    - parent_ptes bit 0 is zero, only one spte points at this pages and
    + parent_ptes bit 0 is zero, only one spte points at this page and
    parent_ptes points at this single spte, otherwise, there exists multiple
    sptes pointing at this page and (parent_ptes & ~0x1) points at a data
    - structure with a list of parent_ptes.
    + structure with a list of parent sptes.
    unsync:
    If true, then the translations in this page may not match the guest's
    translation. This is equivalent to the state of the tlb when a pte is
    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index 3104748..5b249d4 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -1098,17 +1098,23 @@ struct rmap_iterator {
    static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head,
    struct rmap_iterator *iter)
    {
    + u64 *sptep;
    +
    if (!rmap_head->val)
    return NULL;

    if (!(rmap_head->val & 1)) {
    iter->desc = NULL;
    - return (u64 *)rmap_head->val;
    + sptep = (u64 *)rmap_head->val;
    + goto out;
    }

    iter->desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
    iter->pos = 0;
    - return iter->desc->sptes[iter->pos];
    + sptep = iter->desc->sptes[iter->pos];
    +out:
    + BUG_ON(!is_shadow_present_pte(*sptep));
    + return sptep;
    }

    /*
    @@ -1118,14 +1124,14 @@ static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head,
    */
    static u64 *rmap_get_next(struct rmap_iterator *iter)
    {
    + u64 *sptep;
    +
    if (iter->desc) {
    if (iter->pos < PTE_LIST_EXT - 1) {
    - u64 *sptep;
    -
    ++iter->pos;
    sptep = iter->desc->sptes[iter->pos];
    if (sptep)
    - return sptep;
    + goto out;
    }

    iter->desc = iter->desc->more;
    @@ -1133,17 +1139,20 @@ static u64 *rmap_get_next(struct rmap_iterator *iter)
    if (iter->desc) {
    iter->pos = 0;
    /* desc->sptes[0] cannot be NULL */
    - return iter->desc->sptes[iter->pos];
    + sptep = iter->desc->sptes[iter->pos];
    + goto out;
    }
    }

    return NULL;
    +out:
    + BUG_ON(!is_shadow_present_pte(*sptep));
    + return sptep;
    }

    #define for_each_rmap_spte(_rmap_head_, _iter_, _spte_) \
    for (_spte_ = rmap_get_first(_rmap_head_, _iter_); \
    - _spte_ && ({BUG_ON(!is_shadow_present_pte(*_spte_)); 1;}); \
    - _spte_ = rmap_get_next(_iter_))
    + _spte_; _spte_ = rmap_get_next(_iter_))

    static void drop_spte(struct kvm *kvm, u64 *sptep)
    {
    @@ -1358,7 +1367,6 @@ static bool kvm_zap_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head)
    bool flush = false;

    while ((sptep = rmap_get_first(rmap_head, &iter))) {
    - BUG_ON(!(*sptep & PT_PRESENT_MASK));
    rmap_printk("%s: spte %p %llx.\n", __func__, sptep, *sptep);

    drop_spte(kvm, sptep);
    --
    2.1.0


    \
     
     \ /
      Last update: 2015-11-20 10:01    [W:3.755 / U:0.000 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site