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 8DF68C4332F for ; Thu, 1 Dec 2022 23:11:51 +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:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ztysB5ccJvaw4eBiFeI2dmGQt3RampHPPPoM+Zrht9g=; b=gim9y5Nriah+et dNG/FhEyB5Nl38c1eJehzlA2tCsruT/AGMuQcLAMFDxem13qhH7oqdPcf4xT0O92C9+LxnnUzFXYe EqVo65iRRsuBIJYtgPpODaLvdaW+6blhcfs+khTWffzJ/P2c2TqGzXSROsKUQJoWEh+kLlA3lARcu DgXoV7FHIUdRDerXuTno7IGDFfNudy5VtK2pf7+DRWGsE83AxyPwwetLfvF1zXmd3OoSaeKDXvhYs +kzXotrkzYYKgUgduffwSNeJRCDyJ4xV5XWJIQaIRE08yLvLbUjjSGuJgiaQ6/I5tmNC5hO7y0/w5 FLtJEte4/cBWrVYkfQdw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p0shb-00BYqO-Uq; Thu, 01 Dec 2022 23:10:48 +0000 Received: from out2.migadu.com ([2001:41d0:2:aacc::]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1p0oJr-009fC8-BH for linux-arm-kernel@lists.infradead.org; Thu, 01 Dec 2022 18:30:01 +0000 Date: Thu, 1 Dec 2022 18:29:51 +0000 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Marc Zyngier Cc: Akihiko Odaki , linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Mathieu Poirier , Suzuki K Poulose , Alexandru Elisei , James Morse , Will Deacon , Catalin Marinas , asahi@lists.linux.dev, Alyssa Rosenzweig , Sven Peter , Hector Martin Subject: Re: [PATCH 0/3] KVM: arm64: Handle CCSIDR associativity mismatches Message-ID: References: <20221201104914.28944-1-akihiko.odaki@daynix.com> <867czbmlh1.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <867czbmlh1.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221201_102959_797184_BDECEEDC X-CRM114-Status: GOOD ( 11.42 ) 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 Thu, Dec 01, 2022 at 11:06:50AM +0000, Marc Zyngier wrote: [...] > It would be a lot better to expose a virtual topology > (one set, one way, one level). It would also save us from the CCSIDRX > silliness. > > The only complexity would be to still accept different topologies from > userspace so that we can restore a VM saved before this virtual > topology. I generally agree that the reported topology is meaningless to non-secure software. However, with the cloud vendor hat on, I'm worried that inevitably some customer will inspect the cache topology of the VM we've provided them and complain. Could we extend your suggestion about accepting different topologies to effectively tolerate _any_ topology provided by userspace? KVM can default to the virtual topology, but a well-informed userspace could still provide different values to its guest. No point in trying to babyproofing the UAPI further, IMO. -- Thanks, Oliver _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel