[RFC PATCH v5 08/38] KVM: arm64: Unlock memslots after stage 2 tables are freed

[Reiji Watanabe]

Hi Alex,

On 11/17/21 7:38 AM, Alexandru Elisei wrote:
> Unpin the backing pages mapped at stage 2 after the stage 2 translation
> tables are destroyed.
> 
> Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
> ---
>   arch/arm64/kvm/mmu.c | 23 ++++++++++++++++++-----
>   1 file changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index cd6f1bc7842d..072e2aba371f 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1627,11 +1627,19 @@ int kvm_mmu_lock_memslot(struct kvm *kvm, u64 slot, u64 flags)
>   	return ret;
>   }
>   
> -static void unlock_memslot(struct kvm *kvm, struct kvm_memory_slot *memslot)
> +static void __unlock_memslot(struct kvm *kvm, struct kvm_memory_slot *memslot)
>   {
>   	bool writable = memslot->arch.flags & KVM_MEMSLOT_LOCK_WRITE;
>   	unsigned long npages = memslot->npages;
>   
> +	unpin_memslot_pages(memslot, writable);
> +	account_locked_vm(current->mm, npages, false);
> +
> +	memslot->arch.flags &= ~KVM_MEMSLOT_LOCK_MASK;
> +}
> +
> +static void unlock_memslot(struct kvm *kvm, struct kvm_memory_slot *memslot)
> +{
>   	/*
>   	 * MMU maintenace operations aren't performed on an unlocked memslot.
>   	 * Unmap it from stage 2 so the abort handler performs the necessary
> @@ -1640,10 +1648,7 @@ static void unlock_memslot(struct kvm *kvm, struct kvm_memory_slot *memslot)
>   	if (kvm_mmu_has_pending_ops(kvm))
>   		kvm_arch_flush_shadow_memslot(kvm, memslot);
>   
> -	unpin_memslot_pages(memslot, writable);
> -	account_locked_vm(current->mm, npages, false);
> -
> -	memslot->arch.flags &= ~KVM_MEMSLOT_LOCK_MASK;
> +	__unlock_memslot(kvm, memslot);
>   }
>   
>   int kvm_mmu_unlock_memslot(struct kvm *kvm, u64 slot, u64 flags)
> @@ -1951,7 +1956,15 @@ void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
>   
>   void kvm_arch_flush_shadow_all(struct kvm *kvm)
>   {
> +	struct kvm_memory_slot *memslot;
> +
>   	kvm_free_stage2_pgd(&kvm->arch.mmu);
> +
> +	kvm_for_each_memslot(memslot, kvm_memslots(kvm)) {
> +		if (!memslot_is_locked(memslot))
> +			continue;
> +		__unlock_memslot(kvm, memslot);
> +	}
>   }

Perhaps it might be useful to manage the number of locked memslots ?
(can be used in the fix for kvm_mmu_unlock_memslot in the patch-7 as well)
                                                  
Thanks,
Reiji


>   
>   void kvm_arch_flush_shadow_memslot(struct kvm *kvm,