Re: [RFC 41/55] KVM: arm/arm64: Unmap/flush shadow stage 2 page tables

[Christoffer Dall]

On Mon, Jan 09, 2017 at 01:24:37AM -0500, Jintack Lim wrote:
> From: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> 
> Unmap/flush shadow stage 2 page tables for the nested VMs as well as the
> stage 2 page table for the guest hypervisor.
> 
> Note: A bunch of the code in mmu.c relating to MMU notifiers is
> currently dealt with in an extremely abrupt way, for example by clearing
> out an entire shadow stage-2 table.  Probably we can do smarter with
> some sort of rmap structure.

I think we need to do better than this patch for merging something
upstream.  At least the current approach will not perform well if we run
more than one guest hypervisor on the system.

> 
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Signed-off-by: Jintack Lim <jintack@xxxxxxxxxxxxxxx>
> ---
>  arch/arm/include/asm/kvm_mmu.h   |  7 ++++
>  arch/arm/kvm/arm.c               |  6 ++-
>  arch/arm/kvm/mmu.c               | 11 +++++
>  arch/arm64/include/asm/kvm_mmu.h | 13 ++++++
>  arch/arm64/kvm/mmu-nested.c      | 90 ++++++++++++++++++++++++++++++++++++----
>  5 files changed, 117 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index 1b3309c..ae3aa39 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -230,6 +230,13 @@ static inline unsigned int kvm_get_vmid_bits(void)
>  	return 8;
>  }
>  
> +static inline void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu) { }
> +static inline int kvm_nested_s2_init(struct kvm_vcpu *vcpu) { return 0; }
> +static inline void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu) { }
> +static inline void kvm_nested_s2_all_vcpus_wp(struct kvm *kvm) { }
> +static inline void kvm_nested_s2_all_vcpus_unmap(struct kvm *kvm) { }
> +static inline void kvm_nested_s2_all_vcpus_flush(struct kvm *kvm) { }
> +
>  static inline u64 kvm_get_vttbr(struct kvm_s2_vmid *vmid,
>  				struct kvm_s2_mmu *mmu)
>  {
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 6fa5754..dc2795f 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -191,6 +191,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>  
>  	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
>  		if (kvm->vcpus[i]) {
> +			kvm_nested_s2_teardown(kvm->vcpus[i]);
>  			kvm_arch_vcpu_free(kvm->vcpus[i]);
>  			kvm->vcpus[i] = NULL;
>  		}
> @@ -333,6 +334,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
>  
>  	vcpu->arch.hw_mmu = mmu;
>  	vcpu->arch.hw_vttbr = kvm_get_vttbr(&mmu->vmid, mmu);
> +	kvm_nested_s2_init(vcpu);
>  
>  	return 0;
>  }
> @@ -871,8 +873,10 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
>  	 * Ensure a rebooted VM will fault in RAM pages and detect if the
>  	 * guest MMU is turned off and flush the caches as needed.
>  	 */
> -	if (vcpu->arch.has_run_once)
> +	if (vcpu->arch.has_run_once) {
>  		stage2_unmap_vm(vcpu->kvm);
> +		kvm_nested_s2_unmap(vcpu);
> +	}
>  
>  	vcpu_reset_hcr(vcpu);
>  
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 98b42e8..1677a87 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -416,6 +416,8 @@ static void stage2_flush_vm(struct kvm *kvm)
>  	kvm_for_each_memslot(memslot, slots)
>  		stage2_flush_memslot(&kvm->arch.mmu, memslot);
>  
> +	kvm_nested_s2_all_vcpus_flush(kvm);
> +
>  	spin_unlock(&kvm->mmu_lock);
>  	srcu_read_unlock(&kvm->srcu, idx);
>  }
> @@ -1240,6 +1242,7 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot)
>  
>  	spin_lock(&kvm->mmu_lock);
>  	kvm_stage2_wp_range(kvm, &kvm->arch.mmu, start, end);
> +	kvm_nested_s2_all_vcpus_wp(kvm);
>  	spin_unlock(&kvm->mmu_lock);
>  	kvm_flush_remote_tlbs(kvm);
>  }
> @@ -1278,6 +1281,7 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
>  		gfn_t gfn_offset, unsigned long mask)
>  {
>  	kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask);
> +	kvm_nested_s2_all_vcpus_wp(kvm);
>  }
>  
>  static void coherent_cache_guest_page(struct kvm_vcpu *vcpu, kvm_pfn_t pfn,
> @@ -1604,6 +1608,7 @@ static int handle_hva_to_gpa(struct kvm *kvm,
>  static int kvm_unmap_hva_handler(struct kvm *kvm, gpa_t gpa, void *data)
>  {
>  	kvm_unmap_stage2_range(&kvm->arch.mmu, gpa, PAGE_SIZE);
> +	kvm_nested_s2_all_vcpus_unmap(kvm);
>  	return 0;
>  }
>  
> @@ -1642,6 +1647,7 @@ static int kvm_set_spte_handler(struct kvm *kvm, gpa_t gpa, void *data)
>  	 * through this calling path.
>  	 */
>  	stage2_set_pte(&kvm->arch.mmu, NULL, gpa, pte, 0);
> +	kvm_nested_s2_all_vcpus_unmap(kvm);
>  	return 0;
>  }
>  
> @@ -1675,6 +1681,8 @@ static int kvm_age_hva_handler(struct kvm *kvm, gpa_t gpa, void *data)
>  	if (pte_none(*pte))
>  		return 0;
>  
> +	/* TODO: Handle nested_mmu structures here as well */
> +
>  	return stage2_ptep_test_and_clear_young(pte);
>  }
>  
> @@ -1694,6 +1702,8 @@ static int kvm_test_age_hva_handler(struct kvm *kvm, gpa_t gpa, void *data)
>  	if (!pte_none(*pte))		/* Just a page... */
>  		return pte_young(*pte);
>  
> +	/* TODO: Handle nested_mmu structures here as well */

These TODO's should be addresses somehow as well.

> +
>  	return 0;
>  }
>  
> @@ -1959,6 +1969,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>  
>  	spin_lock(&kvm->mmu_lock);
>  	kvm_unmap_stage2_range(&kvm->arch.mmu, gpa, size);
> +	kvm_nested_s2_all_vcpus_unmap(kvm);
>  	spin_unlock(&kvm->mmu_lock);
>  }
>  
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index fdc9327..e4d5d54 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -328,6 +328,12 @@ static inline unsigned int kvm_get_vmid_bits(void)
>  struct kvm_nested_s2_mmu *get_nested_mmu(struct kvm_vcpu *vcpu, u64 vttbr);
>  struct kvm_s2_mmu *vcpu_get_active_s2_mmu(struct kvm_vcpu *vcpu);
>  bool handle_vttbr_update(struct kvm_vcpu *vcpu, u64 vttbr);
> +void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu);
> +int kvm_nested_s2_init(struct kvm_vcpu *vcpu);
> +void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu);
> +void kvm_nested_s2_all_vcpus_wp(struct kvm *kvm);
> +void kvm_nested_s2_all_vcpus_unmap(struct kvm *kvm);
> +void kvm_nested_s2_all_vcpus_flush(struct kvm *kvm);
>  #else
>  static inline struct kvm_nested_s2_mmu *get_nested_mmu(struct kvm_vcpu *vcpu,
>  						       u64 vttbr)
> @@ -343,6 +349,13 @@ static inline bool handle_vttbr_update(struct kvm_vcpu *vcpu, u64 vttbr)
>  {
>  	return false;
>  }
> +
> +static inline void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu) { }
> +static inline int kvm_nested_s2_init(struct kvm_vcpu *vcpu) { return 0; }
> +static inline void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu) { }
> +static inline void kvm_nested_s2_all_vcpus_wp(struct kvm *kvm) { }
> +static inline void kvm_nested_s2_all_vcpus_unmap(struct kvm *kvm) { }
> +static inline void kvm_nested_s2_all_vcpus_flush(struct kvm *kvm) { }
>  #endif
>  
>  static inline u64 kvm_get_vttbr(struct kvm_s2_vmid *vmid,
> diff --git a/arch/arm64/kvm/mmu-nested.c b/arch/arm64/kvm/mmu-nested.c
> index 0811d94..b22b78c 100644
> --- a/arch/arm64/kvm/mmu-nested.c
> +++ b/arch/arm64/kvm/mmu-nested.c
> @@ -1,6 +1,7 @@
>  /*
>   * Copyright (C) 2016 - Columbia University
>   * Author: Jintack Lim <jintack@xxxxxxxxxxxxxxx>
> + * Author: Christoffer Dall <cdall@xxxxxxxxxxxxxxx>
>   *
>   * This program is free software; you can redistribute it and/or modify
>   * it under the terms of the GNU General Public License version 2 as
> @@ -22,6 +23,86 @@
>  #include <asm/kvm_mmu.h>
>  #include <asm/kvm_nested.h>
>  
> +
> +/* expects kvm->mmu_lock to be held */
> +void kvm_nested_s2_all_vcpus_wp(struct kvm *kvm)
> +{
> +	int i;
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_nested_s2_mmu *nested_mmu;
> +	struct list_head *nested_mmu_list;
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		if (need_resched() || spin_needbreak(&kvm->mmu_lock))
> +			cond_resched_lock(&kvm->mmu_lock);
> +
> +		nested_mmu_list = &vcpu->kvm->arch.nested_mmu_list;
> +		list_for_each_entry_rcu(nested_mmu, nested_mmu_list, list)
> +			kvm_stage2_wp_range(kvm, &nested_mmu->mmu,
> +				    0, KVM_PHYS_SIZE);
> +	}
> +}
> +
> +/* expects kvm->mmu_lock to be held */
> +void kvm_nested_s2_all_vcpus_unmap(struct kvm *kvm)
> +{
> +	int i;
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_nested_s2_mmu *nested_mmu;
> +	struct list_head *nested_mmu_list;
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		if (need_resched() || spin_needbreak(&kvm->mmu_lock))
> +			cond_resched_lock(&kvm->mmu_lock);
> +
> +		nested_mmu_list = &vcpu->kvm->arch.nested_mmu_list;
> +		list_for_each_entry_rcu(nested_mmu, nested_mmu_list, list)
> +			kvm_unmap_stage2_range(&nested_mmu->mmu,
> +				       0, KVM_PHYS_SIZE);
> +	}
> +}
> +
> +void kvm_nested_s2_all_vcpus_flush(struct kvm *kvm)
> +{
> +	int i;
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_nested_s2_mmu *nested_mmu;
> +	struct list_head *nested_mmu_list;
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		if (need_resched() || spin_needbreak(&kvm->mmu_lock))
> +			cond_resched_lock(&kvm->mmu_lock);
> +
> +		nested_mmu_list = &vcpu->kvm->arch.nested_mmu_list;
> +		list_for_each_entry_rcu(nested_mmu, nested_mmu_list, list)
> +			kvm_stage2_flush_range(&nested_mmu->mmu,
> +				       0, KVM_PHYS_SIZE);
> +	}
> +}
> +
> +void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_nested_s2_mmu *nested_mmu;
> +	struct list_head *nested_mmu_list = &vcpu->kvm->arch.nested_mmu_list;
> +
> +	list_for_each_entry_rcu(nested_mmu, nested_mmu_list, list)
> +		kvm_unmap_stage2_range(&nested_mmu->mmu, 0, KVM_PHYS_SIZE);
> +}

Did we change the functionality of this function in this patch as well
or are we just moving it around?  I can't really tell.


Thanks,
-Christoffer

> +
> +int kvm_nested_s2_init(struct kvm_vcpu *vcpu)
> +{
> +	return 0;
> +}
> +
> +void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_nested_s2_mmu *nested_mmu;
> +	struct list_head *nested_mmu_list = &vcpu->kvm->arch.nested_mmu_list;
> +
> +	list_for_each_entry_rcu(nested_mmu, nested_mmu_list, list)
> +		__kvm_free_stage2_pgd(&nested_mmu->mmu);
> +}
> +
>  struct kvm_nested_s2_mmu *get_nested_mmu(struct kvm_vcpu *vcpu, u64 vttbr)
>  {
>  	struct kvm_nested_s2_mmu *mmu;
> @@ -89,15 +170,6 @@ static struct kvm_nested_s2_mmu *create_nested_mmu(struct kvm_vcpu *vcpu,
>  	return nested_mmu;
>  }
>  
> -static void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu)
> -{
> -	struct kvm_nested_s2_mmu *nested_mmu;
> -	struct list_head *nested_mmu_list = &vcpu->kvm->arch.nested_mmu_list;
> -
> -	list_for_each_entry_rcu(nested_mmu, nested_mmu_list, list)
> -		kvm_unmap_stage2_range(&nested_mmu->mmu, 0, KVM_PHYS_SIZE);
> -}
> -
>  bool handle_vttbr_update(struct kvm_vcpu *vcpu, u64 vttbr)
>  {
>  	struct kvm_nested_s2_mmu *nested_mmu;
> -- 
> 1.9.1
> 
>