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arm/arm64: KVM: Implement Stage-2 page aging 

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@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
This commit is contained in:
Marc Zyngier 2015-03-12 18:16:51 +00:00 committed by Christoffer Dall
parent 1d2ebaccc7
commit 35307b9a5f
7 changed files with 104 additions and 23 deletions
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1
arch/arm/include/asm/kvm_arm.h
View File

@ -185,6 +185,7 @@
#define HSR_COND (0xfU << HSR_COND_SHIFT)
#define FSC_FAULT (0x04)
#define FSC_ACCESS (0x08)
#define FSC_PERM (0x0c)
/* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */

13
arch/arm/include/asm/kvm_host.h
View File

@ -167,19 +167,10 @@ 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)
{

65
arch/arm/kvm/mmu.c
View File

@ -1299,6 +1299,7 @@ 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;
}
@ -1333,7 +1334,8 @@ 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),
@ -1475,6 +1477,67 @@ 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 */
if (pmd_young(*pmd)) {
*pmd = pmd_mkold(*pmd);
return 1;
}
return 0;
}
pte = pte_offset_kernel(pmd, gpa);
if (pte_none(*pte))
return 0;
if (pte_young(*pte)) {
*pte = pte_mkold(*pte); /* Just a page... */
return 1;
}
return 0;
}
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);

33
arch/arm/kvm/trace.h
View File

@ -210,6 +210,39 @@ 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),

1
arch/arm64/include/asm/esr.h
View File

@ -90,6 +90,7 @@
#define ESR_ELx_FSC (0x3F)
#define ESR_ELx_FSC_TYPE (0x3C)
#define ESR_ELx_FSC_EXTABT (0x10)
#define ESR_ELx_FSC_ACCESS (0x08)
#define ESR_ELx_FSC_FAULT (0x04)
#define ESR_ELx_FSC_PERM (0x0C)
#define ESR_ELx_CV (UL(1) << 24)

1
arch/arm64/include/asm/kvm_arm.h
View File

@ -187,6 +187,7 @@
/* For compatibility with fault code shared with 32-bit */
#define FSC_FAULT ESR_ELx_FSC_FAULT
#define FSC_ACCESS ESR_ELx_FSC_ACCESS
#define FSC_PERM ESR_ELx_FSC_PERM
/* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */

13
arch/arm64/include/asm/kvm_host.h
View File

@ -179,19 +179,10 @@ 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)
{