Until now, KVM/arm didn't care much for page aging (who was swapping
anyway?), and simply provided empty hooks to the core KVM code. With
server-type systems now being available, things are quite different.
This patch implements very simple support for page aging, by clearing
the Access flag in the Stage-2 page tables. On access fault, the current
fault handling will write the PTE or PMD again, putting the Access flag
back on.
It should be possible to implement a much faster handling for Access
faults, but that's left for a later patch.
With this in place, performance in VMs is degraded much more gracefully.
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm/include/asm/kvm_host.h | 13 ++-------
arch/arm/kvm/mmu.c | 59 ++++++++++++++++++++++++++++++++++++++-
arch/arm/kvm/trace.h | 33 ++++++++++++++++++++++
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/include/asm/kvm_host.h | 13 ++-------
5 files changed, 96 insertions(+), 23 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 04b4ea0..d6b5b85 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -163,19 +163,10 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
+int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
/* We do not have shadow page tables, hence the empty hooks */
-static inline int kvm_age_hva(struct kvm *kvm, unsigned long start,
- unsigned long end)
-{
- return 0;
-}
-
-static inline int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
-{
- return 0;
-}
-
static inline void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm,
unsigned long address)
{
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index e163a45..ffe89a0 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1068,6 +1068,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
out_unlock:
spin_unlock(&kvm->mmu_lock);
+ kvm_set_pfn_accessed(pfn);
kvm_release_pfn_clean(pfn);
return ret;
}
@@ -1102,7 +1103,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
/* Check the stage-2 fault is trans. fault or write fault */
fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
- if (fault_status != FSC_FAULT && fault_status != FSC_PERM) {
+ if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
+ fault_status != FSC_ACCESS) {
kvm_err("Unsupported FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",
kvm_vcpu_trap_get_class(vcpu),
(unsigned long)kvm_vcpu_trap_get_fault(vcpu),
@@ -1237,6 +1239,61 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
handle_hva_to_gpa(kvm, hva, end, &kvm_set_spte_handler, &stage2_pte);
}
+static int kvm_age_hva_handler(struct kvm *kvm, gpa_t gpa, void *data)
+{
+ pmd_t *pmd;
+ pte_t *pte;
+
+ pmd = stage2_get_pmd(kvm, NULL, gpa);
+ if (!pmd || pmd_none(*pmd)) /* Nothing there */
+ return 0;
+
+ if (kvm_pmd_huge(*pmd)) { /* THP, HugeTLB */
+ *pmd = pmd_mkold(*pmd);
+ goto tlbi;
+ }
+
+ pte = pte_offset_kernel(pmd, gpa);
+ if (pte_none(*pte))
+ return 0;
+
+ *pte = pte_mkold(*pte); /* Just a page... */
+tlbi:
+ kvm_tlb_flush_vmid_ipa(kvm, gpa);
+ return 1;
+}
+
+static int kvm_test_age_hva_handler(struct kvm *kvm, gpa_t gpa, void *data)
+{
+ pmd_t *pmd;
+ pte_t *pte;
+
+ pmd = stage2_get_pmd(kvm, NULL, gpa);
+ if (!pmd || pmd_none(*pmd)) /* Nothing there */
+ return 0;
+
+ if (kvm_pmd_huge(*pmd)) /* THP, HugeTLB */
+ return pmd_young(*pmd);
+
+ pte = pte_offset_kernel(pmd, gpa);
+ if (!pte_none(*pte)) /* Just a page... */
+ return pte_young(*pte);
+
+ return 0;
+}
+
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
+{
+ trace_kvm_age_hva(start, end);
+ return handle_hva_to_gpa(kvm, start, end, kvm_age_hva_handler, NULL);
+}
+
+int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
+{
+ trace_kvm_test_age_hva(hva);
+ return handle_hva_to_gpa(kvm, hva, hva, kvm_test_age_hva_handler, NULL);
+}
+
void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
diff --git a/arch/arm/kvm/trace.h b/arch/arm/kvm/trace.h
index b6a6e71..364b5382 100644
--- a/arch/arm/kvm/trace.h
+++ b/arch/arm/kvm/trace.h
@@ -203,6 +203,39 @@ TRACE_EVENT(kvm_set_spte_hva,
TP_printk("mmu notifier set pte hva: %#08lx", __entry->hva)
);
+TRACE_EVENT(kvm_age_hva,
+ TP_PROTO(unsigned long start, unsigned long end),
+ TP_ARGS(start, end),
+
+ TP_STRUCT__entry(
+ __field( unsigned long, start )
+ __field( unsigned long, end )
+ ),
+
+ TP_fast_assign(
+ __entry->start = start;
+ __entry->end = end;
+ ),
+
+ TP_printk("mmu notifier age hva: %#08lx -- %#08lx",
+ __entry->start, __entry->end)
+);
+
+TRACE_EVENT(kvm_test_age_hva,
+ TP_PROTO(unsigned long hva),
+ TP_ARGS(hva),
+
+ TP_STRUCT__entry(
+ __field( unsigned long, hva )
+ ),
+
+ TP_fast_assign(
+ __entry->hva = hva;
+ ),
+
+ TP_printk("mmu notifier test age hva: %#08lx", __entry->hva)
+);
+
TRACE_EVENT(kvm_hvc,
TP_PROTO(unsigned long vcpu_pc, unsigned long r0, unsigned long imm),
TP_ARGS(vcpu_pc, r0, imm),
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 8afb863..0d738f2 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -212,6 +212,7 @@
#define FSC_FAULT (0x04)
+#define FSC_ACCESS (0x08)
#define FSC_PERM (0x0c)
/* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index acd101a..b831710 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -173,19 +173,10 @@ int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
int kvm_unmap_hva_range(struct kvm *kvm,
unsigned long start, unsigned long end);
void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
+int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
/* We do not have shadow page tables, hence the empty hooks */
-static inline int kvm_age_hva(struct kvm *kvm, unsigned long start,
- unsigned long end)
-{
- return 0;
-}
-
-static inline int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
-{
- return 0;
-}
-
static inline void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm,
unsigned long address)
{
--
2.1.4
--
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