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Commit 35307b9a authored by Marc Zyngier's avatar Marc Zyngier Committed by Christoffer Dall
Browse files

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: default avatarMarc Zyngier <marc.zyngier@arm.com>
Acked-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent 1d2ebacc

arch/arm/include/asm/kvm_arm.h

+1 −0
Original line number Diff line number Diff line
@@ -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) */

arch/arm/include/asm/kvm_host.h

+2 −11
Original line number Diff line number Diff line
@@ -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)

{

arch/arm/kvm/mmu.c

+64 −1
Original line number Diff line number Diff line
@@ -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);

arch/arm/kvm/trace.h

+33 −0
Original line number Diff line number Diff line
@@ -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),

arch/arm64/include/asm/esr.h

+1 −0
Original line number Diff line number Diff line
@@ -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)