Date:   Fri, 17 Mar 2023 14:18:54 +0800
From:   Yan Zhao <yan.y.zhao@intel.com>
To:     Sean Christopherson <seanjc@google.com>
CC:     Paolo Bonzini <pbonzini@redhat.com>,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Zhi Wang <zhi.a.wang@intel.com>, <kvm@vger.kernel.org>,
        <intel-gvt-dev@lists.freedesktop.org>,
        <intel-gfx@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH v2 06/27] drm/i915/gvt: Put the page reference obtained
 by KVM's gfn_to_pfn()
Message-ID: <ZBQGTjKqXJT4U7fj@yzhao56-desk.sh.intel.com>
Reply-To: Yan Zhao <yan.y.zhao@intel.com>
References: <20230311002258.852397-1-seanjc@google.com>
 <20230311002258.852397-7-seanjc@google.com>
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Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>

On Fri, Mar 10, 2023 at 04:22:37PM -0800, Sean Christopherson wrote:
> Put the struct page reference acquired by gfn_to_pfn(), KVM's API is that
> the caller is ultimately responsible for dropping any reference.
> 
> Note, kvm_release_pfn_clean() ensures the pfn is actually a refcounted
> struct page before trying to put any references.
> 
> Fixes: b901b252b6cf ("drm/i915/gvt: Add 2M huge gtt support")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  drivers/gpu/drm/i915/gvt/gtt.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index d59c7ab9d224..15848b041a0d 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -1160,6 +1160,7 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
>  	unsigned long gfn = ops->get_pfn(entry);
>  	kvm_pfn_t pfn;
>  	int max_level;
> +	int ret;
>  
>  	if (!HAS_PAGE_SIZES(vgpu->gvt->gt->i915, I915_GTT_PAGE_SIZE_2M))
>  		return 0;
> @@ -1179,7 +1180,9 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
>  	if (!pfn_valid(pfn))
>  		return -EINVAL;
>  
> -	return PageTransHuge(pfn_to_page(pfn));
> +	ret = PageTransHuge(pfn_to_page(pfn));
> +	kvm_release_pfn_clean(pfn);
> +	return ret;
>  }
>  
>  static int split_2MB_gtt_entry(struct intel_vgpu *vgpu,
> -- 
> 2.40.0.rc1.284.g88254d51c5-goog
>