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Fri, 17 Sep 2021 17:50:56 +0000 Subject: Re: [PATCH] xen/x86: fix PV trap handling on secondary processors To: Juergen Gross , Jan Beulich Cc: Stefano Stabellini , lkml , "xen-devel@lists.xenproject.org" References: <34898e9c-5883-a978-98ee-b81b22d8caed@suse.com> <823f4ef4-f9e5-68cb-d6e9-d079483c1e21@oracle.com> <0afce6e8-3c8a-e5ae-cd54-0fd598276506@suse.com> <62ccf5b7-b903-e604-d113-67c7633278cd@suse.com> <2c4549c8-bdeb-3584-95c4-7076b7cf79bb@suse.com> <35835650-bbbb-7dbd-061b-693f39f9453e@suse.com> From: Boris Ostrovsky Message-ID: <1bdda8a5-4748-6791-58a9-b1e342281b01@oracle.com> Date: Fri, 17 Sep 2021 13:50:54 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 In-Reply-To: <35835650-bbbb-7dbd-061b-693f39f9453e@suse.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-ClientProxiedBy: BL1PR13CA0201.namprd13.prod.outlook.com (2603:10b6:208:2be::26) To BLAPR10MB5009.namprd10.prod.outlook.com (2603:10b6:208:321::10) MIME-Version: 1.0 Received: from [10.74.115.10] (138.3.201.10) by BL1PR13CA0201.namprd13.prod.outlook.com (2603:10b6:208:2be::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4544.6 via Frontend Transport; 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>>>>>> +    unsigned i, count = (desc->size + 1) / sizeof(gate_desc); >>>>>>    -    xen_convert_trap_info(desc, traps); >>>>> >>>>> >>>>> Can you instead add a boolean parameter to xen_convert_trap_info() to indicate whether to skip empty entries? That will avoid (almost) duplicating the code. >>>> >>>> I can, sure, but I specifically didn't, as the result is going to be less >>>> readable imo. Instead I was considering to fold xen_convert_trap_info() >>>> into its only remaining caller. Yet if you're convinced adding the >>>> parameter is the way to do, I will go that route. But please confirm. Yes, that would be my preference. No preference on where to set the sentinel. Thanks. -boris >>> >>> I don't think the result will be very hard to read. All you need is the >>> new parameter and extending the if statement in xen_convert_trap_info() >>> to increment out always if no entry is to be skipped. >> >> And skip writing the sentinel. > > Maybe it would be even better then to let xen_convert_trap_info() return > the number of entries written and to write the sentinel in > xen_load_idt() instead, as this is the only place where it is needed. > > > Juergen