linux-kernel - Re: [PATCH v4 05/29] drm/i915/gvt: Put the page reference obtained by KVM's gfn_to

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Date:   Tue, 1 Aug 2023 14:25:49 +0300
From:   "Wang, Zhi A" <zhi.a.wang@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>
CC:     <kvm@...r.kernel.org>, <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Yan Zhao <yan.y.zhao@...el.com>,
        Yongwei Ma <yongwei.ma@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v4 05/29] drm/i915/gvt: Put the page reference obtained by
 KVM's gfn_to_pfn()

On 7/29/2023 4:35 AM, 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")
> Reviewed-by: Yan Zhao <yan.y.zhao@...el.com>
> Tested-by: Yongwei Ma <yongwei.ma@...el.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.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 f30922c55a0c..5426a27c1b71 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -1158,6 +1158,7 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
>   {
>   	const struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
>   	kvm_pfn_t pfn;
> +	int ret;
>   
>   	if (!HAS_PAGE_SIZES(vgpu->gvt->gt->i915, I915_GTT_PAGE_SIZE_2M))
>   		return 0;
> @@ -1171,7 +1172,9 @@ 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,

Reviewed-by: Zhi Wang <zhi.a.wang@...el.com>