[PATCH v13 83/85] KVM: arm64: Don't mark "struct page" accessed when making SPTE young

Sean Christopherson
2024-10-10T19:55:24Z

Don't mark pages/folios as accessed in the primary MMU when making a SPTE
young in KVM's secondary MMU, as doing so relies on
kvm_pfn_to_refcounted_page(), and generally speaking is unnecessary and
wasteful. KVM participates in page aging via mmu_notifiers, so there's no
need to push "accessed" updates to the primary MMU.

Dropping use of kvm_set_pfn_accessed() also paves the way for removing
kvm_pfn_to_refcounted_page() and all its users.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/include/asm/kvm_pgtable.h | 4 +---
arch/arm64/kvm/hyp/pgtable.c | 7 ++-----
arch/arm64/kvm/mmu.c | 6 +-----
3 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 03f4c3d7839c..aab04097b505 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -674,10 +674,8 @@ int kvm_pgtable_stage2_wrprotect(struct kvm_pgtable *pgt, u64 addr, u64 size);
*
* If there is a valid, leaf page-table entry used to translate @addr, then
* set the access flag in that entry.
- *
- * Return: The old page-table entry prior to setting the flag, 0 on failure.
*/
-kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr);
+void kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr);

/**
* kvm_pgtable_stage2_test_clear_young() - Test and optionally clear the access
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index b11bcebac908..40bd55966540 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -1245,19 +1245,16 @@ int kvm_pgtable_stage2_wrprotect(struct kvm_pgtable *pgt, u64 addr, u64 size)
NULL, NULL, 0);
}

-kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
+void kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
{
- kvm_pte_t pte = 0;
int ret;

ret = stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
- &pte, NULL,
+ NULL, NULL,
KVM_PGTABLE_WALK_HANDLE_FAULT |
KVM_PGTABLE_WALK_SHARED);
if (!ret)
dsb(ishst);
-
- return pte;
}

struct stage2_age_data {
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 4054356c9712..e2ae9005e333 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1706,18 +1706,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
/* Resolve the access fault by making the page young again. */
static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
{
- kvm_pte_t pte;
struct kvm_s2_mmu *mmu;

trace_kvm_access_fault(fault_ipa);

read_lock(&vcpu->kvm->mmu_lock);
mmu = vcpu->arch.hw_mmu;
- pte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
+ kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
read_unlock(&vcpu->kvm->mmu_lock);
-
- if (kvm_pte_valid(pte))
- kvm_set_pfn_accessed(kvm_pte_to_pfn(pte));
}

/**