Re: [PATCH 3/4] kvm: Create non-coherent DMA registeration

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 10/02/2013 06:15 AM, Alex Williamson wrote:
> We currently use some ad-hoc arch variables tied to legacy KVM device
> assignment to manage emulation of instructions that depend on whether
> non-coherent DMA is present.  Create an interface for this so that we
> can register coherency for other devices, like vfio assigned devices.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |    2 ++
>  arch/x86/kvm/vmx.c              |    3 +--
>  arch/x86/kvm/x86.c              |   21 +++++++++++++++++++--
>  include/linux/kvm_host.h        |   19 +++++++++++++++++++
>  virt/kvm/iommu.c                |    6 ++++++
>  5 files changed, 47 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1b6b5f9..50c1e9c1 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -558,6 +558,8 @@ struct kvm_arch {
>  	struct list_head assigned_dev_head;
>  	struct iommu_domain *iommu_domain;
>  	bool iommu_noncoherent;
> +#define __KVM_HAVE_ARCH_NONCOHERENT_DMA
> +	atomic_t noncoherent_dma_count;
>  	struct kvm_pic *vpic;
>  	struct kvm_ioapic *vioapic;
>  	struct kvm_pit *vpit;
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 8b2270a..a982c9e 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7404,8 +7404,7 @@ static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
>  	 */
>  	if (is_mmio)
>  		ret = MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT;
> -	else if (vcpu->kvm->arch.iommu_domain &&
> -		 vcpu->kvm->arch.iommu_noncoherent)
> +	else if (kvm_arch_has_noncoherent_dma(vcpu->kvm))
>  		ret = kvm_get_guest_memory_type(vcpu, gfn) <<
>  		      VMX_EPT_MT_EPTE_SHIFT;
>  	else
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b1231b0..feec86d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2715,8 +2715,7 @@ static void wbinvd_ipi(void *garbage)
>  
>  static bool need_emulate_wbinvd(struct kvm_vcpu *vcpu)
>  {
> -	return vcpu->kvm->arch.iommu_domain &&
> -	       vcpu->kvm->arch.iommu_noncoherent;
> +	return kvm_arch_has_noncoherent_dma(vcpu->kvm);
>  }
>  
>  void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> @@ -7420,6 +7419,24 @@ bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu)
>  			kvm_x86_ops->interrupt_allowed(vcpu);
>  }
>  
> +void kvm_arch_register_noncoherent_dma(struct kvm *kvm)
> +{
> +	atomic_inc(&kvm->arch.noncoherent_dma_count);
> +}
> +EXPORT_SYMBOL_GPL(kvm_arch_register_noncoherent_dma);
> +
> +void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm)
> +{
> +	atomic_dec(&kvm->arch.noncoherent_dma_count);
> +}
> +EXPORT_SYMBOL_GPL(kvm_arch_unregister_noncoherent_dma);
> +
> +bool kvm_arch_has_noncoherent_dma(struct kvm *kvm)
> +{
> +	return atomic_read(&kvm->arch.noncoherent_dma_count);
> +}
> +EXPORT_SYMBOL_GPL(kvm_arch_has_noncoherent_dma);
> +
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index f46da56..e239c93 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -671,6 +671,25 @@ static inline void kvm_arch_free_vm(struct kvm *kvm)
>  }
>  #endif
>  
> +#ifdef __KVM_HAVE_ARCH_NONCOHERENT_DMA
> +void kvm_arch_register_noncoherent_dma(struct kvm *kvm);
> +void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm);
> +bool kvm_arch_has_noncoherent_dma(struct kvm *kvm);
> +#else
> +static inline void kvm_arch_register_noncoherent_dma(void)


Wrong prototype here and below, must include *kvm.


> +{
> +}
> +
> +static inline void kvm_arch_unregister_noncoherent_dma(void)
> +{
> +}
> +
> +static inline bool kvm_arch_has_noncoherent_dma(void)
> +{
> +	return false;
> +}
> +#endif
> +
>  static inline wait_queue_head_t *kvm_arch_vcpu_wq(struct kvm_vcpu *vcpu)
>  {
>  #ifdef __KVM_HAVE_ARCH_WQP
> diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
> index 9cde444..0a54456 100644
> --- a/virt/kvm/iommu.c
> +++ b/virt/kvm/iommu.c
> @@ -140,6 +140,9 @@ static int kvm_iommu_map_memslots(struct kvm *kvm)
>  	struct kvm_memslots *slots;
>  	struct kvm_memory_slot *memslot;
>  
> +	if (kvm->arch.iommu_noncoherent)
> +		kvm_arch_register_noncoherent_dma(kvm);
> +
>  	idx = srcu_read_lock(&kvm->srcu);
>  	slots = kvm_memslots(kvm);
>  
> @@ -335,6 +338,9 @@ static int kvm_iommu_unmap_memslots(struct kvm *kvm)
>  
>  	srcu_read_unlock(&kvm->srcu, idx);
>  
> +	if (kvm->arch.iommu_noncoherent)
> +		kvm_arch_unregister_noncoherent_dma(kvm);
> +
>  	return 0;
>  }
>  
> 


-- 
Alexey