linux-kernel - Re: [PATCH v9 4/6] KVM: Migrate kvm_vcpu_map to __kvm_follow

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Date:   Tue, 03 Oct 2023 19:54:40 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     David Stevens <stevensd@...omium.org>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v9 4/6] KVM: Migrate kvm_vcpu_map to __kvm_follow_pfn

У пн, 2023-09-11 у 11:16 +0900, David Stevens пише:
> From: David Stevens <stevensd@...omium.org>
> 
> Migrate kvm_vcpu_map to __kvm_follow_pfn. Track is_refcounted_page so
> that kvm_vcpu_unmap know whether or not it needs to release the page.
> 
> Signed-off-by: David Stevens <stevensd@...omium.org>
> ---
>  include/linux/kvm_host.h |  2 +-
>  virt/kvm/kvm_main.c      | 24 ++++++++++++++----------
>  2 files changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2ed08ae1a9be..b95c79b7833b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -294,6 +294,7 @@ struct kvm_host_map {
>  	void *hva;
>  	kvm_pfn_t pfn;
>  	kvm_pfn_t gfn;
> +	bool is_refcounted_page;
>  };
>  
>  /*
> @@ -1228,7 +1229,6 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn);
>  void kvm_set_pfn_dirty(kvm_pfn_t pfn);
>  void kvm_set_pfn_accessed(kvm_pfn_t pfn);
>  
> -void kvm_release_pfn(kvm_pfn_t pfn, bool dirty);
>  int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
>  			int len);
>  int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 235c5cb3fdac..913de4e86d9d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2886,24 +2886,22 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
>  }
>  EXPORT_SYMBOL_GPL(gfn_to_page);
>  
> -void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
> -{
> -	if (dirty)
> -		kvm_release_pfn_dirty(pfn);
> -	else
> -		kvm_release_pfn_clean(pfn);
> -}
> -
>  int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
>  {
>  	kvm_pfn_t pfn;
>  	void *hva = NULL;
>  	struct page *page = KVM_UNMAPPED_PAGE;
> +	struct kvm_follow_pfn foll = {
> +		.slot = gfn_to_memslot(vcpu->kvm, gfn),
> +		.gfn = gfn,
> +		.flags = FOLL_WRITE,
> +		.allow_non_refcounted_struct_page = true,
> +	};
>  
>  	if (!map)
>  		return -EINVAL;
>  
> -	pfn = gfn_to_pfn(vcpu->kvm, gfn);
> +	pfn = __kvm_follow_pfn(&foll);
>  	if (is_error_noslot_pfn(pfn))
>  		return -EINVAL;
>  
> @@ -2923,6 +2921,7 @@ int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
>  	map->hva = hva;
>  	map->pfn = pfn;
>  	map->gfn = gfn;
> +	map->is_refcounted_page = foll.is_refcounted_page;
>  
>  	return 0;
>  }
> @@ -2946,7 +2945,12 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
>  	if (dirty)
>  		kvm_vcpu_mark_page_dirty(vcpu, map->gfn);
>  
> -	kvm_release_pfn(map->pfn, dirty);
> +	if (map->is_refcounted_page) {
> +		if (dirty)
> +			kvm_release_page_dirty(map->page);
> +		else
> +			kvm_release_page_clean(map->page);
> +	}
>  
>  	map->hva = NULL;
>  	map->page = NULL;

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky