From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 465A2C433EF for ; Tue, 17 May 2022 16:49:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:Cc:To:Subject:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=LwQ8IcZNzkdlF1dJOLE4UMO95+n30870zBoRuUBG0Do=; b=Z7glauchvT7i8kSerDD8QYoMNl 2RFL1bJHczez31FUrDCIL/C0ZZwDlRUgISBkgvmXxDspCfzHK9fOU/Co5oIvxWvHm6oNwxz5ou/d5 bIig9Ro/OY3tA+Lh3uOxLlSDZjhGEHcvKkEaqfTBWJdCX4lY4x6+pG5IXbENjFKg3pmyusrNzXwik YJ8yh+dyHEU8ThAcm8QxJ/9zZ4+yyEkn3YiPvZRBxfFG+k35T5Nwfx8HlNC0oSKlOVWG1VvWnTx9u 6GvtdnZdOC02dB/pm5XvvmY1m2fHzdOCYzZVVJdZB3mRR/TSTJ15At3cG4rdR3atZxMBLuyV0RwnK HA1A5NIw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nr0Mt-00EuQb-QW; Tue, 17 May 2022 16:48:19 +0000 Received: from outgoing-stata.csail.mit.edu ([128.30.2.210]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nr0Mq-00EuNz-Cy for linux-arm-kernel@lists.infradead.org; Tue, 17 May 2022 16:48:18 +0000 Received: from c-24-16-96-21.hsd1.wa.comcast.net ([24.16.96.21] helo=srivatsab-a02.vmware.com) by outgoing-stata.csail.mit.edu with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1nr0Md-000E5Y-3n; Tue, 17 May 2022 12:48:03 -0400 Subject: Re: [PATCH v3] arm64: paravirt: Use RCU read locks to guard stolen_time To: Will Deacon Cc: Elliot Berman , Juergen Gross , Alexey Makhalov , Catalin Marinas , Prakruthi Deepak Heragu , virtualization@lists.linux-foundation.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Murali Nalajala References: <20220513174654.362169-1-quic_eberman@quicinc.com> <20220517085418.GA3169@willie-the-truck> From: "Srivatsa S. Bhat" Message-ID: <1dc10835-e302-8ae7-c256-efb0c420f35a@csail.mit.edu> Date: Tue, 17 May 2022 09:48:00 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20220517085418.GA3169@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220517_094816_552676_854CEDD6 X-CRM114-Status: GOOD ( 12.53 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/17/22 1:54 AM, Will Deacon wrote: > On Fri, May 13, 2022 at 04:32:53PM -0700, Srivatsa S. Bhat wrote: >> On 5/13/22 10:46 AM, Elliot Berman wrote: >>> From: Prakruthi Deepak Heragu >>> [...] >>> static int stolen_time_cpu_down_prepare(unsigned int cpu) >>> { >>> + struct pvclock_vcpu_stolen_time *kaddr = NULL; >>> struct pv_time_stolen_time_region *reg; >>> >>> reg = this_cpu_ptr(&stolen_time_region); >>> if (!reg->kaddr) >>> return 0; >>> >>> - memunmap(reg->kaddr); >>> - memset(reg, 0, sizeof(*reg)); >>> + kaddr = rcu_replace_pointer(reg->kaddr, NULL, true); >>> + synchronize_rcu(); >>> + memunmap(kaddr); >>> >> >> The original code used to memset the stolen time region, but this >> patch seems to drop it. Was that change intentional? > > 'struct pv_time_stolen_time_region' only has one field ('kaddr'), which > we're now clearing with rcu_replace_pointer() so the memset doesn't make > sense. > Ah right, never mind :) Thank you! Regards, Srivatsa _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel