From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB0CD10798; Thu, 1 Dec 2022 23:14:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D45EC433D6; Thu, 1 Dec 2022 23:14:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669936489; bh=sW2w9vG53AsHMr88biNtK5xVlmmBmRvG3cpj2Bp8Jg4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rsthgWMx6bnE+lspTiwU+KDdWOou+nBiG3jBf5wj014VIwGxMiGdpV0oRwYMbTQhb ZL0lRC49+Aq+/cPwWa63O2wtLQlh6jnj1ogAw12hQA7fMVGdJAnuRdy49S75f786Ph zNF7ejF1U0y7fcmlqghsZZoMx57g/TNk6H2DSbzsWvuxke0S8psrF2s5eznardWAXR aaE11RfDe/Gsb0L3onC8e+fvwJ11mKK9LgoxzrDNMgv9xOau9QBaZx7PwiaTrLBe83 ICp/+PraeAlJ8qLbEftISRM3qylUs/D2MwvJ0tUJi71BOk9/SzCDLqD5JgBPWlRJbj ucGRYQH0OBf8A== Received: from 51-171-6-54-dynamic.agg9.chf.chf-qkr.eircom.net ([51.171.6.54] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1p0slT-009wHo-7n; Thu, 01 Dec 2022 23:14:47 +0000 Date: Thu, 01 Dec 2022 23:14:43 +0000 Message-ID: <87k03au36k.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton 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 In-Reply-To: References: <20221201104914.28944-1-akihiko.odaki@daynix.com> <867czbmlh1.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: asahi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 51.171.6.54 X-SA-Exim-Rcpt-To: oliver.upton@linux.dev, akihiko.odaki@daynix.com, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, mathieu.poirier@linaro.org, suzuki.poulose@arm.com, alexandru.elisei@arm.com, james.morse@arm.com, will@kernel.org, catalin.marinas@arm.com, asahi@lists.linux.dev, alyssa@rosenzweig.io, sven@svenpeter.dev, marcan@marcan.st X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Thu, 01 Dec 2022 18:29:51 +0000, Oliver Upton wrote: > > 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. That's their prerogative. It is idiotic, but I guess paying customers get this privilege ;-). > 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. I think this is *exactly* what I suggested. Any valid topology should be able to be restored, as we currently present the VM with any topology the host HW may have. This must be preserved. Eventually, we may even have to expose CCSIDRX, but let's cross that bridge when we get to it. Thanks, M. -- Without deviation from the norm, progress is not possible. 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 mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91308C4332F for ; Thu, 1 Dec 2022 23:14:56 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 328E44B248; Thu, 1 Dec 2022 18:14:56 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Z3Y2mr09BQDu; Thu, 1 Dec 2022 18:14:54 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E3D514A0D8; Thu, 1 Dec 2022 18:14:54 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 792524A0D8 for ; Thu, 1 Dec 2022 18:14:53 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id gapOFMwdm3w3 for ; Thu, 1 Dec 2022 18:14:52 -0500 (EST) Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 15E53403C4 for ; Thu, 1 Dec 2022 18:14:52 -0500 (EST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D3BC1B81F50; Thu, 1 Dec 2022 23:14:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D45EC433D6; Thu, 1 Dec 2022 23:14:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669936489; bh=sW2w9vG53AsHMr88biNtK5xVlmmBmRvG3cpj2Bp8Jg4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rsthgWMx6bnE+lspTiwU+KDdWOou+nBiG3jBf5wj014VIwGxMiGdpV0oRwYMbTQhb ZL0lRC49+Aq+/cPwWa63O2wtLQlh6jnj1ogAw12hQA7fMVGdJAnuRdy49S75f786Ph zNF7ejF1U0y7fcmlqghsZZoMx57g/TNk6H2DSbzsWvuxke0S8psrF2s5eznardWAXR aaE11RfDe/Gsb0L3onC8e+fvwJ11mKK9LgoxzrDNMgv9xOau9QBaZx7PwiaTrLBe83 ICp/+PraeAlJ8qLbEftISRM3qylUs/D2MwvJ0tUJi71BOk9/SzCDLqD5JgBPWlRJbj ucGRYQH0OBf8A== Received: from 51-171-6-54-dynamic.agg9.chf.chf-qkr.eircom.net ([51.171.6.54] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1p0slT-009wHo-7n; Thu, 01 Dec 2022 23:14:47 +0000 Date: Thu, 01 Dec 2022 23:14:43 +0000 Message-ID: <87k03au36k.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton Subject: Re: [PATCH 0/3] KVM: arm64: Handle CCSIDR associativity mismatches In-Reply-To: References: <20221201104914.28944-1-akihiko.odaki@daynix.com> <867czbmlh1.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 51.171.6.54 X-SA-Exim-Rcpt-To: oliver.upton@linux.dev, akihiko.odaki@daynix.com, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, mathieu.poirier@linaro.org, suzuki.poulose@arm.com, alexandru.elisei@arm.com, james.morse@arm.com, will@kernel.org, catalin.marinas@arm.com, asahi@lists.linux.dev, alyssa@rosenzweig.io, sven@svenpeter.dev, marcan@marcan.st X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: Alyssa Rosenzweig , Hector Martin , Akihiko Odaki , Mathieu Poirier , Will Deacon , Sven Peter , linux-kernel@vger.kernel.org, asahi@lists.linux.dev, Catalin Marinas , kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Thu, 01 Dec 2022 18:29:51 +0000, Oliver Upton wrote: > > 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. That's their prerogative. It is idiotic, but I guess paying customers get this privilege ;-). > 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. I think this is *exactly* what I suggested. Any valid topology should be able to be restored, as we currently present the VM with any topology the host HW may have. This must be preserved. Eventually, we may even have to expose CCSIDRX, but let's cross that bridge when we get to it. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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 EA419C4332F for ; Thu, 1 Dec 2022 23:47:47 +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:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; 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Thu, 1 Dec 2022 23:14:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D45EC433D6; Thu, 1 Dec 2022 23:14:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669936489; bh=sW2w9vG53AsHMr88biNtK5xVlmmBmRvG3cpj2Bp8Jg4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rsthgWMx6bnE+lspTiwU+KDdWOou+nBiG3jBf5wj014VIwGxMiGdpV0oRwYMbTQhb ZL0lRC49+Aq+/cPwWa63O2wtLQlh6jnj1ogAw12hQA7fMVGdJAnuRdy49S75f786Ph zNF7ejF1U0y7fcmlqghsZZoMx57g/TNk6H2DSbzsWvuxke0S8psrF2s5eznardWAXR aaE11RfDe/Gsb0L3onC8e+fvwJ11mKK9LgoxzrDNMgv9xOau9QBaZx7PwiaTrLBe83 ICp/+PraeAlJ8qLbEftISRM3qylUs/D2MwvJ0tUJi71BOk9/SzCDLqD5JgBPWlRJbj ucGRYQH0OBf8A== Received: from 51-171-6-54-dynamic.agg9.chf.chf-qkr.eircom.net ([51.171.6.54] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1p0slT-009wHo-7n; Thu, 01 Dec 2022 23:14:47 +0000 Date: Thu, 01 Dec 2022 23:14:43 +0000 Message-ID: <87k03au36k.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton 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 In-Reply-To: References: <20221201104914.28944-1-akihiko.odaki@daynix.com> <867czbmlh1.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 51.171.6.54 X-SA-Exim-Rcpt-To: oliver.upton@linux.dev, akihiko.odaki@daynix.com, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, mathieu.poirier@linaro.org, suzuki.poulose@arm.com, alexandru.elisei@arm.com, james.morse@arm.com, will@kernel.org, catalin.marinas@arm.com, asahi@lists.linux.dev, alyssa@rosenzweig.io, sven@svenpeter.dev, marcan@marcan.st X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221201_151452_634109_6D6DC4E5 X-CRM114-Status: GOOD ( 24.28 ) 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, 01 Dec 2022 18:29:51 +0000, Oliver Upton wrote: > > 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. That's their prerogative. It is idiotic, but I guess paying customers get this privilege ;-). > 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. I think this is *exactly* what I suggested. Any valid topology should be able to be restored, as we currently present the VM with any topology the host HW may have. This must be preserved. Eventually, we may even have to expose CCSIDRX, but let's cross that bridge when we get to it. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel