From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753442AbcADUlj (ORCPT ); Mon, 4 Jan 2016 15:41:39 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:51547 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751431AbcADUlf (ORCPT ); Mon, 4 Jan 2016 15:41:35 -0500 From: Joao Martins Subject: Re: [PATCH RFC 2/3] x86/xen/time: setup vcpu 0 time info page To: Boris Ostrovsky , linux-kernel@vger.kernel.org, xen-devel@lists.xen.org References: <1451339557-24473-1-git-send-email-joao.m.martins@oracle.com> <1451339557-24473-3-git-send-email-joao.m.martins@oracle.com> <568A98D9.9090501@oracle.com> Cc: Konrad Rzeszutek Wilk , David Vrabel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org Message-ID: <568AD8F3.2050600@oracle.com> Date: Mon, 4 Jan 2016 20:41:23 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.4.0 MIME-Version: 1.0 In-Reply-To: <568A98D9.9090501@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/04/2016 04:07 PM, Boris Ostrovsky wrote: > On 12/28/2015 04:52 PM, Joao Martins wrote: >> + >> +static int xen_setup_vsyscall_time_info(int cpu) >> +{ >> + struct pvclock_vsyscall_time_info *ti; >> + struct vcpu_register_time_memory_area t; >> + struct pvclock_vcpu_time_info *pvti; >> + unsigned long mem; >> + int ret, size; >> + u8 flags; >> + >> + ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, >> + cpu, NULL); >> + if (ret == -ENOSYS) { >> + pr_debug("xen: vcpu_time_info placement not supported\n"); >> + return -ENOTSUPP; >> + } > > I don't think this is necessary. > OK, I will remove it. >> + >> + size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)); >> + mem = memblock_alloc(size, PAGE_SIZE); >> + if (!mem) >> + return -ENOMEM; >> + >> + ti = __va(mem); >> + memset(ti, 0, size); > > Can you just use get_zeroed_page()? (struct pvclock_vsyscall_time_info > is always less than a page, isn't it?). Yeah, I can use get_zeroed_page() (struct pvclock_vsyscall_time_info is always less than a page). Additionally perhaps this region shouldn't be freed if PVCLOCK_TSC_STABLE_BIT isn't supported, because otherwise I would end up corrupting data elsewhere since the pvti would still be periodically updated by Xen, right? > > > -boris >