Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <a1d56c78-fff2-0c98-48dd-e4d66b1437e5@intel.com>
Date:   Tue, 1 Aug 2023 14:25:49 +0300
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.13.0
Subject: Re: [PATCH v4 05/29] drm/i915/gvt: Put the page reference obtained by
 KVM's gfn_to_pfn()
Content-Language: en-US
To:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Zhenyu Wang <zhenyuw@linux.intel.com>
CC:     <kvm@vger.kernel.org>, <intel-gvt-dev@lists.freedesktop.org>,
        <intel-gfx@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        Yan Zhao <yan.y.zhao@intel.com>,
        Yongwei Ma <yongwei.ma@intel.com>,
        Ben Gardon <bgardon@google.com>
References: <20230729013535.1070024-1-seanjc@google.com>
 <20230729013535.1070024-6-seanjc@google.com>
From:   "Wang, Zhi A" <zhi.a.wang@intel.com>
In-Reply-To: <20230729013535.1070024-6-seanjc@google.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?K3JnSW83VHl3emhwUkx5VnBXMGdmS1hpM2NkaWRydkFRNmNWdkZLTDFxL3hN?=
 =?utf-8?B?UnpBQVJZR3Aycmh1amhlQjRuZ0JQOUFzc1NQRkVLb25GcnFPYVN0Nkc2Yy8v?=
 =?utf-8?B?eWJwUVNNeU1YVXVxd054SGowWVNxcHQrTXIwVU1UODJKZTF5RTE5RDl3RFB4?=
 =?utf-8?B?YjFZdG9mREFSTk11cDFrY0c4bnlqZzlhY2xqcU1Sbzl1Nm5lZFB2UCt0QUFm?=
 =?utf-8?B?VXlneDZ4a3NwejVXcHMyd3FZdnhXWGFFZUdGU1dsOU1qcU9DajdKVVlIakpa?=
 =?utf-8?B?WlQwci82YjVmWnVsRU4vN0VjbFNCM3RhYWJ5aVhZMEpMRFV2VkNkc2RmMk9B?=
 =?utf-8?B?bDV2QlhVaE9zVHorQ2pZYXUzWGpVeWptZ3B4UEpReEt5MnZhcGNwK3RMdWZz?=
 =?utf-8?B?YjBkS0J0VjJ3YzF0Q0pBdUtqaWdwOE85K3RnaTl4dHcwTTlTS05RRlZWRzNC?=
 =?utf-8?B?RVR2aFhTTzlQSVAybUhFOW5kRzA5aWtBN2dEdHRPWEVKcTc0NXJLVTk2bDh5?=
 =?utf-8?B?THdCSnlndENId3poM3Uzb2kycnoyRGx6UHB4TWZNVVJuNjZIbnpseUVuWXIy?=
 =?utf-8?B?d0VOdmNNK1hmblVFS0FVaVFlM0xDOFFUK1lHTnpkWUMrbnlTV2FaVWNZU0dm?=
 =?utf-8?B?bVkybStxb0UvK2JmU0NOVjh5ZlZYVU1td1FVSC9zd3BiQVYzb3Z2dmFJN3B5?=
 =?utf-8?B?V3lRQ1lXeUZjUXRqeUVsbC91SnE3N0txWHB2RVp1b1kzUHZqSkpzUmo2SDl2?=
 =?utf-8?B?WmtwQ0xnU3pkTklEUnV5ZVBlcVJmd3hZdnZHMkt1QnVtSzZ1SlArSWRrdGg5?=
 =?utf-8?B?c2xsV1NqVExoSGJRUC9DQzJwWTdaeFlUMHlSMTB5YmpzUFFIb2tZTnExN05y?=
 =?utf-8?B?dTh3WlQzTU9JSnhrV1FVTStJNVJXb09GajJiL3RoNEROTzMwa3pLQmxMR0lO?=
 =?utf-8?B?SjdKQnl4UHd0K1lWVzFWbWtFVUViazlvTXB2T3NiTzRUQWpLS3oyZytBK29h?=
 =?utf-8?B?Kzl1cHl1clZYQVVlcVM4V3pIbFBNT1YxVFdXamF5RWRJa3dmZjBjdS9GZnhh?=
 =?utf-8?B?L2ZhT3JiQUVHejZlTGZYZVpPUzNOd3I5bVFBT2JkeVJhL1FQQWpNdzU2OExY?=
 =?utf-8?B?eVNxRGc5OExTR3J2NC8zTjhFWVRVR3p1UThwcWVjQmRJYXA5WHVlYll3aXJa?=
 =?utf-8?B?RWNhQTlITytlZkladnAyY3ltVU9WU0ZNTWlZSUR0UTBQS1BvWEltMnp3V01Y?=
 =?utf-8?B?VGptdFZla2IzTGlHZXFVWUtxOS8rWTc3YkZFcitoUFpHWU40UXUvK3NwcUVL?=
 =?utf-8?B?cmhIRFkxaHI4dXA5UjJKY3l0VFJqOVJWWDZsZ1hwOFpNeFJuSlh6VFRkeDRJ?=
 =?utf-8?B?K2ZqUW1QNHpTS1A5cHJkemJiRU1uQzNjSXN4emhJSHBPc1Z3YVN3eldpenVx?=
 =?utf-8?B?d1JaTnVMdlhIZDlYR0lORzFSRTBrMlgxbmw5bmVWcWcvMVBSMFBFSmxQY2Zs?=
 =?utf-8?B?ZGR0SVpabm84b3dDOEMzVEIxZUEySWp1dG1wUld2U0dZK3pyM0pBdS9MR3JE?=
 =?utf-8?B?M1hDY2VpeG9KS0Z2YzllOWhvYmVnbFFEV2NtOVZ5dis4R1V5djZTZzd4L3dE?=
 =?utf-8?B?QWZQRzFLa1U1MU5NQmZmbzBNdEdvQTRMZWxVZWZSVytPc1JHUzZna2tYNVl5?=
 =?utf-8?B?Z2NDa0pkUmhmSE8xOXo4cjZhTGpNNWtkdVpuY3Nyek11TUdBQ1p3UGlaZUY0?=
 =?utf-8?B?Rzhtc3A5akc5RUxMS2pmYVVoMENuaEJob1NGbFVCWE5CTi9hemJRclBQd1Rm?=
 =?utf-8?B?RzBHZTVHNVRoWUc0NjBQNGNvemlDQ1FpWW1kSm5PTExqM1NzamVlc2NLZ2ZB?=
 =?utf-8?B?OTNxYWo5RWZDNG5PTU5Hdk9MNHFDa0ZRVWl3ekJJaTh3QzQ4MzA1TE9pcCtG?=
 =?utf-8?B?OWNaUnlDNWg3SUJINVcxVXIzM2x0RFJoejJ1Mkg3WWNtZjZ0Y1JpaDYwWnM3?=
 =?utf-8?B?TWZ6WlZLd01qa01mamMyTjM3c1NsZUhVbTRQSEtPRFl3Z0VDOUZWT0hSOENZ?=
 =?utf-8?B?STVkSlJjbXlmZVJQZ2J5SVE0WnRBeHFxeDdxS1Zvby9va0M4SEdoQi9VczBY?=
 =?utf-8?Q?PKEwnt/AdHDdsMPl0iiIHdqrp?=
X-MS-Exchange-CrossTenant-Network-Message-Id: eafc120c-94be-4187-f369-08db9282125c
X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB5549.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Aug 2023 11:25:55.6758
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: Iei5C2hBbzIgLuBCw4aW2yZJsmDGwBLm1hHLrJOSgpAq4tVjKhOh+AtwLWI4ZTG+5FIxRIBuhnJ+SzphzeGAOg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR11MB7204
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,
        RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no
        version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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@intel.com>
> Tested-by: Yongwei Ma <yongwei.ma@intel.com>
> 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 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@intel.com>