In shadow page table, only leaf SPs may be marked as unsync; instead, for non-leaf SPs, we store the number of unsynced children in unsync_children. Therefore, in kvm_mmu_sync_root(), sp->unsync shall always be zero for the root SP and there is no need to check it. Remove the check, and add a warning inside mmu_sync_children() to assert that the flags are used properly.
While at it, move the warning from mmu_need_write_protect() to kvm_unsync_page(). Co-developed-by: Sean Christopherson <[email protected]> Signed-off-by: Sean Christopherson <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> Signed-off-by: Yu Zhang <[email protected]> --- arch/x86/kvm/mmu/mmu.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 86af58294272..5f482af125b4 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu, LIST_HEAD(invalid_list); bool flush = false; + /* + * Only 4k SPTEs can directly be made unsync, the parent pages + * should never be unsyc'd. + */ + WARN_ON_ONCE(parent->unsync); + while (mmu_unsync_walk(parent, &pages)) { bool protected = false; @@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page); static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { + WARN_ON(sp->role.level != PG_LEVEL_4K); + trace_kvm_mmu_unsync_page(sp); ++vcpu->kvm->stat.mmu_unsync; sp->unsync = 1; @@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, if (sp->unsync) continue; - WARN_ON(sp->role.level != PG_LEVEL_4K); kvm_unsync_page(vcpu, sp); } @@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu) * mmu_need_write_protect() describe what could go wrong if this * requirement isn't satisfied. */ - if (!smp_load_acquire(&sp->unsync) && - !smp_load_acquire(&sp->unsync_children)) + if (!smp_load_acquire(&sp->unsync_children)) return; write_lock(&vcpu->kvm->mmu_lock); -- 2.17.1
