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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQof1-0003iJ-TU; Fri, 09 Oct 2020 09:26:00 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 73EC9301A42; Fri, 9 Oct 2020 11:25:59 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5C16229E7878A; Fri, 9 Oct 2020 11:25:59 +0200 (CEST) Date: Fri, 9 Oct 2020 11:25:59 +0200 From: Peter Zijlstra To: Morten Rasmussen Subject: Re: [RFC PATCH 3/3] arm64: Handle AArch32 tasks running on non AArch32 cpu Message-ID: <20201009092559.GE2628@hirez.programming.kicks-ass.net> References: <20201008181641.32767-1-qais.yousef@arm.com> <20201008181641.32767-4-qais.yousef@arm.com> <20201009072943.GD2628@hirez.programming.kicks-ass.net> <20201009081312.GA8004@e123083-lin> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201009081312.GA8004@e123083-lin> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Catalin Marinas , Marc Zyngier , Linus Torvalds , Greg Kroah-Hartman , Will Deacon , Qais Yousef , linux-arm-kernel@lists.infradead.org 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 Fri, Oct 09, 2020 at 10:13:12AM +0200, Morten Rasmussen wrote: > On Fri, Oct 09, 2020 at 09:29:43AM +0200, Peter Zijlstra wrote: > > Fundamentally, you're not supposed to change the userspace provided > > affinity mask. If we want to do something like this, we'll have to teach > > the scheduler about this second mask such that it can compute an > > effective mask as the intersection between the 'feature' and user mask. > > I agree that we shouldn't mess wit the user-space mask directly. Would it > be unthinkable to go down the route of maintaining a new mask which is > the intersection of the feature mask (controlled and updated by arch > code) and the user-space mask? > > It shouldn't add overhead in the scheduler as it would use the > intersection mask instead of the user-space mask, the main complexity > would be around making sure the intersection mask is updated correctly > (cpusets, hotplug, ...). IFF we _need_ to go there, then yes that was the plan, compose the intersection when either the (arch) feature(set) mask or the userspace mask changes. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel