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David Alan Gilbert" , Markus Armbruster References: <20201126151734.743849-1-andrey.gruzdev@virtuozzo.com> <20201126151734.743849-3-andrey.gruzdev@virtuozzo.com> <20201127210400.GF6573@xz-x1> <20201130153419.GA3277@xz-x1> From: Andrey Gruzdev Message-ID: Date: Mon, 30 Nov 2020 21:41:44 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 In-Reply-To: <20201130153419.GA3277@xz-x1> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [95.165.26.68] X-ClientProxiedBy: AM0PR08CA0035.eurprd08.prod.outlook.com (2603:10a6:208:d2::48) To VI1PR0802MB2510.eurprd08.prod.outlook.com (2603:10a6:800:ad::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.64] (95.165.26.68) by AM0PR08CA0035.eurprd08.prod.outlook.com (2603:10a6:208:d2::48) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3611.20 via Frontend Transport; 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envelope-from=andrey.gruzdev@virtuozzo.com; helo=EUR05-VI1-obe.outbound.protection.outlook.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 30.11.2020 18:34, Peter Xu wrote: > On Sun, Nov 29, 2020 at 11:12:10PM +0300, Andrey Gruzdev wrote: >>>> +void ram_write_tracking_stop(void) >>>> +{ >>>> +#ifdef CONFIG_LINUX >>>> + RAMState *rs = ram_state; >>>> + RAMBlock *bs; >>>> + assert(rs->uffdio_fd >= 0); >>> >>> Maybe too harsh - we can return if it's invalid. >>> >>> Meanwhile, better rcu_read_lock(), as well? >>> >> >> Yep, RCU lock, I'll add. Why too harsh? Just a debug assertion. > > I was afraid some special path could trigger ram_write_tracking_stop() being > called before ram_write_tracking_start(), then vm could crash. If we can > guarantee that not happening, then it's also ok with assert(). > > [...] > It can't really happen, but I agree that assert() is a bit excessive here. >>>> +/** >>>> + * uffd_poll_events: poll UFFD file descriptor for read >>>> + * >>>> + * Returns true if events are available for read, false otherwise >>>> + * >>>> + * @uffd: UFFD file descriptor >>>> + * @tmo: timeout in milliseconds, 0 for non-blocking operation, >>>> + * negative value for infinite wait >>>> + */ >>>> +bool uffd_poll_events(int uffd, int tmo) >>> >>> Shall we spell "tmo" out? >> In the comment? I think it's ok. > > I'd suggest to spell it out everywhere, especially in the codes. But feel free > to take your own preference. Thanks, > Thanks, -- Andrey Gruzdev, Principal Engineer Virtuozzo GmbH +7-903-247-6397 virtuzzo.com