Commit edb298c6 authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range 

This together with previous patch, ensures that
kvm_zap_gfn_range doesn't race with page fault
running on another vcpu, and will make this page fault code
retry instead.

This is based on a patch suggested by Sean Christopherson:
https://lkml.org/lkml/2021/7/22/1025



Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210810205251.424103-5-mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 88f58535

arch/x86/kvm/mmu/mmu.c

+4 −0
Original line number Diff line number Diff line
@@ -5688,6 +5688,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) 


	write_lock(&kvm->mmu_lock);



	kvm_inc_notifier_count(kvm, gfn_start, gfn_end);



	if (kvm_memslots_have_rmaps(kvm)) {

		for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {

			slots = __kvm_memslots(kvm, i);
@@ -5723,6 +5725,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) 
	if (flush)

		kvm_flush_remote_tlbs_with_address(kvm, gfn_start, gfn_end);



	kvm_dec_notifier_count(kvm, gfn_start, gfn_end);



	write_unlock(&kvm->mmu_lock);

}

include/linux/kvm_host.h

+5 −0
Original line number Diff line number Diff line
@@ -991,6 +991,11 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc); 
void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);

#endif



void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,

				   unsigned long end);

void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,

				   unsigned long end);



long kvm_arch_dev_ioctl(struct file *filp,

			unsigned int ioctl, unsigned long arg);

long kvm_arch_vcpu_ioctl(struct file *filp,

virt/kvm/kvm_main.c

+5 −2
Original line number Diff line number Diff line
@@ -610,7 +610,7 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn, 
	kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn);

}



static void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,

void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,

				   unsigned long end)

{

	/*
@@ -638,6 +638,7 @@ static void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start, 
			max(kvm->mmu_notifier_range_end, end);

	}

}

EXPORT_SYMBOL_GPL(kvm_inc_notifier_count);



static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,

					const struct mmu_notifier_range *range)
@@ -672,7 +673,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, 
	return 0;

}



static void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,

void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,

				   unsigned long end)

{

	/*
@@ -689,6 +690,8 @@ static void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start, 
	 */

	kvm->mmu_notifier_count--;

}

EXPORT_SYMBOL_GPL(kvm_dec_notifier_count);





static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,

					const struct mmu_notifier_range *range)