Commit bbc13ae5 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

VFIO: KVM: x86: Drop kvm_arch_{start,end}_assignment() 

Drop kvm_arch_{start,end}_assignment() and all associated code now that
KVM x86 no longer consumes assigned_device_count.  Tracking whether or not
a VFIO-assigned device is formally associated with a VM is fundamentally
flawed, as such an association is optional for general usage, i.e. is prone
to false negatives.  E.g. prior to commit 2edd9cb7 ("kvm: detect
assigned device via irqbypass manager"), device passthrough via VFIO would
fail to enable IRQ bypass if userspace omitted the formal VFIO<=>KVM
binding.

And device drivers that *need* the VFIO<=>KVM connection, e.g. KVM-GT,
shouldn't be relying on generic x86 tracking infrastructure.

Cc: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20250523011756.3243624-6-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent ff845e6a

arch/x86/include/asm/kvm_host.h

+0 −2
Original line number Diff line number Diff line
@@ -1381,8 +1381,6 @@ struct kvm_arch { 


#define __KVM_HAVE_ARCH_NONCOHERENT_DMA

	atomic_t noncoherent_dma_count;

#define __KVM_HAVE_ARCH_ASSIGNED_DEVICE

	atomic_t assigned_device_count;

	unsigned long nr_possible_bypass_irqs;



#ifdef CONFIG_KVM_IOAPIC

arch/x86/kvm/x86.c

+0 −18
Original line number Diff line number Diff line
@@ -13438,24 +13438,6 @@ bool kvm_arch_can_dequeue_async_page_present(struct kvm_vcpu *vcpu) 
		return kvm_lapic_enabled(vcpu) && apf_pageready_slot_free(vcpu);

}



void kvm_arch_start_assignment(struct kvm *kvm)

{

	atomic_inc(&kvm->arch.assigned_device_count);

}

EXPORT_SYMBOL_GPL(kvm_arch_start_assignment);



void kvm_arch_end_assignment(struct kvm *kvm)

{

	atomic_dec(&kvm->arch.assigned_device_count);

}

EXPORT_SYMBOL_GPL(kvm_arch_end_assignment);



bool noinstr kvm_arch_has_assigned_device(struct kvm *kvm)

{

	return raw_atomic_read(&kvm->arch.assigned_device_count);

}

EXPORT_SYMBOL_GPL(kvm_arch_has_assigned_device);



static void kvm_noncoherent_dma_assignment_start_or_stop(struct kvm *kvm)

{

	/*

include/linux/kvm_host.h

+0 −18
Original line number Diff line number Diff line
@@ -1690,24 +1690,6 @@ static inline bool kvm_arch_has_noncoherent_dma(struct kvm *kvm) 
	return false;

}

#endif

#ifdef __KVM_HAVE_ARCH_ASSIGNED_DEVICE

void kvm_arch_start_assignment(struct kvm *kvm);

void kvm_arch_end_assignment(struct kvm *kvm);

bool kvm_arch_has_assigned_device(struct kvm *kvm);

#else

static inline void kvm_arch_start_assignment(struct kvm *kvm)

{

}



static inline void kvm_arch_end_assignment(struct kvm *kvm)

{

}



static __always_inline bool kvm_arch_has_assigned_device(struct kvm *kvm)

{

	return false;

}

#endif



static inline struct rcuwait *kvm_arch_vcpu_get_wait(struct kvm_vcpu *vcpu)

{

virt/kvm/vfio.c

+0 −3
Original line number Diff line number Diff line
@@ -175,7 +175,6 @@ static int kvm_vfio_file_add(struct kvm_device *dev, unsigned int fd) 
	kvf->file = get_file(filp);

	list_add_tail(&kvf->node, &kv->file_list);



	kvm_arch_start_assignment(dev->kvm);

	kvm_vfio_file_set_kvm(kvf->file, dev->kvm);

	kvm_vfio_update_coherency(dev);
@@ -205,7 +204,6 @@ static int kvm_vfio_file_del(struct kvm_device *dev, unsigned int fd) 
			continue;



		list_del(&kvf->node);

		kvm_arch_end_assignment(dev->kvm);

#ifdef CONFIG_SPAPR_TCE_IOMMU

		kvm_spapr_tce_release_vfio_group(dev->kvm, kvf);

#endif
@@ -336,7 +334,6 @@ static void kvm_vfio_release(struct kvm_device *dev) 
		fput(kvf->file);

		list_del(&kvf->node);

		kfree(kvf);

		kvm_arch_end_assignment(dev->kvm);

	}



	kvm_vfio_update_coherency(dev);