From: Ben Gardon <bgardon@google.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Peter Shier <pshier@google.com>,
Peter Feiner <pfeiner@google.com>,
Junaid Shahid <junaids@google.com>,
Jim Mattson <jmattson@google.com>,
Yulei Zhang <yulei.kernel@gmail.com>,
Wanpeng Li <kernellwp@gmail.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
Ben Gardon <bgardon@google.com>
Subject: [PATCH 07/13] KVM: x86/mmu: Make TDP MMU root refcount atomic
Date: Wed, 31 Mar 2021 14:08:35 -0700 [thread overview]
Message-ID: <20210331210841.3996155-8-bgardon@google.com> (raw)
In-Reply-To: <20210331210841.3996155-1-bgardon@google.com>
In order to parallelize more operations for the TDP MMU, make the
refcount on TDP MMU roots atomic, so that a future patch can allow
multiple threads to take a reference on the root concurrently, while
holding the MMU lock in read mode.
Signed-off-by: Ben Gardon <bgardon@google.com>
---
arch/x86/kvm/mmu/mmu_internal.h | 6 +++++-
arch/x86/kvm/mmu/tdp_mmu.c | 15 ++++++++-------
arch/x86/kvm/mmu/tdp_mmu.h | 9 +++------
3 files changed, 16 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 788dcf77c957..0a040d6a4f35 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -50,7 +50,11 @@ struct kvm_mmu_page {
u64 *spt;
/* hold the gfn of each spte inside spt */
gfn_t *gfns;
- int root_count; /* Currently serving as active root */
+ /* Currently serving as active root */
+ union {
+ int root_count;
+ refcount_t tdp_mmu_root_count;
+ };
unsigned int unsync_children;
struct kvm_rmap_head parent_ptes; /* rmap pointers to parent sptes */
DECLARE_BITMAP(unsync_child_bitmap, 512);
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index ab1d26b40164..1f0b2d6124a2 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -56,7 +56,7 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root)
lockdep_assert_held_write(&kvm->mmu_lock);
- if (--root->root_count)
+ if (!refcount_dec_and_test(&root->tdp_mmu_root_count))
return;
WARN_ON(!root->tdp_mmu_page);
@@ -88,10 +88,12 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
next_root = list_first_entry(&kvm->arch.tdp_mmu_roots,
typeof(*next_root), link);
+ while (!list_entry_is_head(next_root, &kvm->arch.tdp_mmu_roots, link) &&
+ !kvm_tdp_mmu_get_root(kvm, next_root))
+ next_root = list_next_entry(next_root, link);
+
if (list_entry_is_head(next_root, &kvm->arch.tdp_mmu_roots, link))
next_root = NULL;
- else
- kvm_tdp_mmu_get_root(kvm, next_root);
if (prev_root)
kvm_tdp_mmu_put_root(kvm, prev_root);
@@ -158,14 +160,13 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
/* Check for an existing root before allocating a new one. */
for_each_tdp_mmu_root(kvm, root) {
- if (root->role.word == role.word) {
- kvm_tdp_mmu_get_root(kvm, root);
+ if (root->role.word == role.word &&
+ kvm_tdp_mmu_get_root(kvm, root))
goto out;
- }
}
root = alloc_tdp_mmu_page(vcpu, 0, vcpu->arch.mmu->shadow_root_level);
- root->root_count = 1;
+ refcount_set(&root->tdp_mmu_root_count, 1);
list_add(&root->link, &kvm->arch.tdp_mmu_roots);
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index 5d950e987fc7..9961df505067 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -7,13 +7,10 @@
hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
-static inline void kvm_tdp_mmu_get_root(struct kvm *kvm,
- struct kvm_mmu_page *root)
+__must_check static inline bool kvm_tdp_mmu_get_root(struct kvm *kvm,
+ struct kvm_mmu_page *root)
{
- BUG_ON(!root->root_count);
- lockdep_assert_held(&kvm->mmu_lock);
-
- ++root->root_count;
+ return refcount_inc_not_zero(&root->tdp_mmu_root_count);
}
void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root);
--
2.31.0.291.g576ba9dcdaf-goog
next prev parent reply other threads:[~2021-03-31 21:09 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-31 21:08 [PATCH 00/13] More parallel operations for the TDP MMU Ben Gardon
2021-03-31 21:08 ` [PATCH 01/13] KVM: x86/mmu: Re-add const qualifier in kvm_tdp_mmu_zap_collapsible_sptes Ben Gardon
2021-03-31 21:08 ` [PATCH 02/13] KVM: x86/mmu: Move kvm_mmu_(get|put)_root to TDP MMU Ben Gardon
2021-03-31 21:08 ` [PATCH 03/13] KVM: x86/mmu: use tdp_mmu_free_sp to free roots Ben Gardon
2021-03-31 21:08 ` [PATCH 04/13] KVM: x86/mmu: Merge TDP MMU put and free root Ben Gardon
2021-03-31 21:08 ` [PATCH 05/13] KVM: x86/mmu: comment for_each_tdp_mmu_root requires MMU write lock Ben Gardon
2021-03-31 21:08 ` [PATCH 06/13] KVM: x86/mmu: Refactor yield safe root iterator Ben Gardon
2021-03-31 21:08 ` Ben Gardon [this message]
2021-03-31 22:21 ` [PATCH 07/13] KVM: x86/mmu: Make TDP MMU root refcount atomic Sean Christopherson
2021-04-01 16:50 ` Ben Gardon
2021-03-31 21:08 ` [PATCH 08/13] KVM: x86/mmu: Protect the tdp_mmu_roots list with RCU Ben Gardon
2021-04-01 9:37 ` Paolo Bonzini
2021-04-01 16:48 ` Ben Gardon
2021-04-01 13:16 ` kernel test robot
2021-04-01 16:50 ` Ben Gardon
2021-03-31 21:08 ` [PATCH 09/13] KVM: x86/mmu: Allow zap gfn range to operate under the mmu read lock Ben Gardon
2021-04-01 9:58 ` Paolo Bonzini
2021-04-01 16:50 ` Ben Gardon
2021-03-31 21:08 ` [PATCH 10/13] KVM: x86/mmu: Allow zapping collapsible SPTEs to use MMU " Ben Gardon
2021-04-01 10:12 ` Paolo Bonzini
2021-03-31 21:08 ` [PATCH 11/13] KVM: x86/mmu: Allow enabling / disabling dirty logging under " Ben Gardon
2021-03-31 21:08 ` [PATCH 12/13] KVM: x86/mmu: Fast invalidation for TDP MMU Ben Gardon
2021-03-31 22:27 ` Sean Christopherson
2021-04-01 16:50 ` Ben Gardon
2021-04-01 10:36 ` Paolo Bonzini
2021-04-01 16:50 ` Ben Gardon
2021-04-01 17:02 ` Paolo Bonzini
2021-03-31 21:08 ` [PATCH 13/13] KVM: x86/mmu: Tear down roots in fast invalidation thread Ben Gardon
2021-03-31 22:29 ` Sean Christopherson
2021-04-01 10:41 ` Paolo Bonzini
2021-04-01 10:37 ` Paolo Bonzini
2021-04-01 10:43 ` [PATCH 00/13] More parallel operations for the TDP MMU Paolo Bonzini
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