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Tue, 4 Sep 2018 01:12:02 -0700 Received: from shsmsx102.ccr.corp.intel.com ([169.254.2.226]) by SHSMSX104.ccr.corp.intel.com ([169.254.5.143]) with mapi id 14.03.0319.002; Tue, 4 Sep 2018 16:12:01 +0800 From: "Peng, DongX" To: Nikita Leshenko , "Wu, Fengguang" CC: Andrew Morton , Linux Memory Management List , "Liu, Jingqi" , "Dong, Eddie" , "Hansen, Dave" , "Huang, Ying" , Brendan Gregg , "kvm@vger.kernel.org" , LKML Subject: RE: [RFC][PATCH 3/5] [PATCH 3/5] kvm-ept-idle: HVA indexed EPT read Thread-Topic: [RFC][PATCH 3/5] [PATCH 3/5] kvm-ept-idle: HVA indexed EPT read Thread-Index: AQHUQmOmnZsRsVJTp0KJvY5txETrBqTfPtWAgACKFLA= Date: Tue, 4 Sep 2018 08:12:00 +0000 Message-ID: <5249147EF0246348BBCB3713DC3757BF8D0D0C@shsmsx102.ccr.corp.intel.com> References: <20180901112818.126790961@intel.com> <20180901124811.591511876@intel.com> <37B30FD3-7955-4C0B-AAB5-544359F4D157@oracle.com> In-Reply-To: <37B30FD3-7955-4C0B-AAB5-544359F4D157@oracle.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ctpclassification: CTP_NT x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiYmJiODY5MWYtYjYyNC00NzBiLTljOWUtMGE3ODE0OTEzNGZmIiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX05UIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE3LjEwLjE4MDQuNDkiLCJUcnVzdGVkTGFiZWxIYXNoIjoiZW9YMk4zUHhSU0pUcHdVR0daMkRvcmNSZytOYUh0VWZabW1XODBUUzNrWE93OTllQndaTGdLTDRyUnozNjZSaiJ9 dlp-product: dlpe-windows dlp-version: 11.0.400.15 dlp-reaction: no-action x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kvm_get_kvm() kvm_put_kvm() -----Original Message----- From: Nikita Leshenko [mailto:nikita.leshchenko@oracle.com] Sent: Tuesday, September 4, 2018 3:57 PM To: Wu, Fengguang Cc: Andrew Morton ; Linux Memory Management List ; Peng, DongX ; Liu, Jingqi ; Dong, Eddie ; Hansen, Dave ; Huang, Ying ; Brendan Gregg ; kvm@vger.kernel.org; LKML Subject: Re: [RFC][PATCH 3/5] [PATCH 3/5] kvm-ept-idle: HVA indexed EPT read On 1 Sep 2018, at 13:28, Fengguang Wu wrote: > +static ssize_t ept_idle_read(struct file *file, char *buf, > + size_t count, loff_t *ppos) > +{ > + struct task_struct *task = file->private_data; > + struct ept_idle_ctrl *eic; > + unsigned long hva_start = *ppos << BITMAP_BYTE2PVA_SHIFT; > + unsigned long hva_end = hva_start + (count << BITMAP_BYTE2PVA_SHIFT); > + int ret; > + > + if (*ppos % IDLE_BITMAP_CHUNK_SIZE || > + count % IDLE_BITMAP_CHUNK_SIZE) > + return -EINVAL; > + > + eic = kzalloc(sizeof(*eic), GFP_KERNEL); > + if (!eic) > + return -EBUSY; > + > + eic->buf = buf; > + eic->buf_size = count; > + eic->kvm = task_kvm(task); > + if (!eic->kvm) { > + ret = -EINVAL; > + goto out_free; > + } I think you need to increment the refcount while using kvm, otherwise kvm can be destroyed from another thread while you're walking it. -Nikita > + > + ret = ept_idle_walk_hva_range(eic, hva_start, hva_end); > + if (ret) > + goto out_free; > + > + ret = eic->bytes_copied; > + *ppos += ret; > +out_free: > + kfree(eic); > + > + return ret; > +}