From: Vipin Sharma <vipinsh@google.com>
To: seanjc@google.com, pbonzini@redhat.com, bgardon@google.com,
dmatlack@google.com
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Vipin Sharma <vipinsh@google.com>
Subject: [Patch v3 1/7] KVM: x86/mmu: Add a helper function to check if an SPTE needs atomic write
Date: Fri, 10 Feb 2023 17:46:20 -0800 [thread overview]
Message-ID: <20230211014626.3659152-2-vipinsh@google.com> (raw)
In-Reply-To: <20230211014626.3659152-1-vipinsh@google.com>
Move conditions in kvm_tdp_mmu_write_spte() to check if an SPTE should
be written atomically or not to a separate function.
This new function, kvm_tdp_mmu_spte_need_atomic_write(), will be used
in future commits to optimize clearing bits in SPTEs.
Signed-off-by: Vipin Sharma <vipinsh@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
---
arch/x86/kvm/mmu/tdp_iter.h | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
index f0af385c56e0..c11c5d00b2c1 100644
--- a/arch/x86/kvm/mmu/tdp_iter.h
+++ b/arch/x86/kvm/mmu/tdp_iter.h
@@ -29,23 +29,29 @@ static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte)
WRITE_ONCE(*rcu_dereference(sptep), new_spte);
}
+/*
+ * SPTEs must be modified atomically if they are shadow-present, leaf
+ * SPTEs, and have volatile bits, i.e. has bits that can be set outside
+ * of mmu_lock. The Writable bit can be set by KVM's fast page fault
+ * handler, and Accessed and Dirty bits can be set by the CPU.
+ *
+ * Note, non-leaf SPTEs do have Accessed bits and those bits are
+ * technically volatile, but KVM doesn't consume the Accessed bit of
+ * non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit. This
+ * logic needs to be reassessed if KVM were to use non-leaf Accessed
+ * bits, e.g. to skip stepping down into child SPTEs when aging SPTEs.
+ */
+static inline bool kvm_tdp_mmu_spte_need_atomic_write(u64 old_spte, int level)
+{
+ return is_shadow_present_pte(old_spte) &&
+ is_last_spte(old_spte, level) &&
+ spte_has_volatile_bits(old_spte);
+}
+
static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte,
u64 new_spte, int level)
{
- /*
- * Atomically write the SPTE if it is a shadow-present, leaf SPTE with
- * volatile bits, i.e. has bits that can be set outside of mmu_lock.
- * The Writable bit can be set by KVM's fast page fault handler, and
- * Accessed and Dirty bits can be set by the CPU.
- *
- * Note, non-leaf SPTEs do have Accessed bits and those bits are
- * technically volatile, but KVM doesn't consume the Accessed bit of
- * non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit. This
- * logic needs to be reassessed if KVM were to use non-leaf Accessed
- * bits, e.g. to skip stepping down into child SPTEs when aging SPTEs.
- */
- if (is_shadow_present_pte(old_spte) && is_last_spte(old_spte, level) &&
- spte_has_volatile_bits(old_spte))
+ if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level))
return kvm_tdp_mmu_write_spte_atomic(sptep, new_spte);
__kvm_tdp_mmu_write_spte(sptep, new_spte);
--
2.39.1.581.gbfd45094c4-goog
next prev parent reply other threads:[~2023-02-11 1:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-11 1:46 [Patch v3 0/7] Optimize clear dirty log Vipin Sharma
2023-02-11 1:46 ` Vipin Sharma [this message]
2023-02-11 1:46 ` [Patch v3 2/7] KVM: x86/mmu: Atomically clear SPTE dirty state in the clear-dirty-log flow Vipin Sharma
2023-02-15 21:12 ` David Matlack
2023-03-17 22:59 ` Sean Christopherson
2023-03-17 23:50 ` Vipin Sharma
2023-02-11 1:46 ` [Patch v3 3/7] KVM: x86/mmu: Remove "record_dirty_log" in __tdp_mmu_set_spte() Vipin Sharma
2023-02-15 21:10 ` David Matlack
2023-02-11 1:46 ` [Patch v3 4/7] KVM: x86/mmu: Optimize SPTE change for aging gfn range Vipin Sharma
2023-02-15 21:15 ` David Matlack
2023-03-21 0:51 ` Sean Christopherson
2023-02-11 1:46 ` [Patch v3 5/7] KVM: x86/mmu: Remove "record_acc_track" in __tdp_mmu_set_spte() Vipin Sharma
2023-02-22 19:31 ` David Matlack
2023-02-11 1:46 ` [Patch v3 6/7] KVM: x86/mmu: Remove handle_changed_spte_dirty_log() Vipin Sharma
2023-02-22 19:36 ` David Matlack
2023-02-11 1:46 ` [Patch v3 7/7] KVM: x86/mmu: Merge all handle_changed_pte* functions Vipin Sharma
2023-02-22 19:42 ` David Matlack
2023-03-17 22:51 ` Sean Christopherson
2023-03-17 23:48 ` Vipin Sharma
2023-03-17 22:57 ` [Patch v3 0/7] Optimize clear dirty log Sean Christopherson
2023-03-17 23:51 ` Vipin Sharma
2023-03-21 0:41 ` Sean Christopherson
2023-03-21 18:11 ` Vipin Sharma
2023-03-21 19:57 ` Sean Christopherson
2023-03-21 20:40 ` Sean Christopherson
2023-03-21 21:38 ` Sean Christopherson
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