KVM: x86/mmu: Allow yielding during MMU notifier unmap/zap, if possible

Let the TDP MMU yield when unmapping a range in response to a MMU
notification, if yielding is allowed by said notification.  There is no
reason to disallow yielding in this case, and in theory the range being
invalidated could be quite large.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210402005658.3024832-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index ea15f3098eb26d87d97c586961fec04e44bd87af..10cb16c55dd03c88fb0acacd15e5a6ba5b396b6d 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -880,7 +880,7 @@ bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range,
 
        for_each_tdp_mmu_root(kvm, root, range->slot->as_id)
                flush |= zap_gfn_range(kvm, root, range->start, range->end,
-                                      false, flush);
+                                      range->may_block, flush);
 
        return flush;
 }
@@ -898,6 +898,10 @@ static __always_inline bool kvm_tdp_mmu_handle_gfn(struct kvm *kvm,
 
        rcu_read_lock();
 
+       /*
+        * Don't support rescheduling, none of the MMU notifiers that funnel
+        * into this helper allow blocking; it'd be dead, wasteful code.
+        */
        for_each_tdp_mmu_root(kvm, root, range->slot->as_id) {
                tdp_root_for_each_leaf_pte(iter, root, range->start, range->end)
                        ret |= handler(kvm, &iter, range);