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Fri, 04 Jun 2021 13:54:49 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lpAHd-00Do8G-Bv for linux-arm-kernel@lists.infradead.org; Fri, 04 Jun 2021 13:54:46 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6F33F613F3; Fri, 4 Jun 2021 13:54:40 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lpAHV-005UZU-Tf; Fri, 04 Jun 2021 14:54:38 +0100 Date: Fri, 04 Jun 2021 14:54:37 +0100 Message-ID: <87sg1xzqea.wl-maz@kernel.org> From: Marc Zyngier To: Shameerali Kolothum Thodi Cc: "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.cs.columbia.edu" , "linux-kernel@vger.kernel.org" , "will@kernel.org" , "catalin.marinas@arm.com" , "james.morse@arm.com" , "julien.thierry.kdev@gmail.com" , "suzuki.poulose@arm.com" , "jean-philippe@linaro.org" , Alexandru Elisei , Linuxarm Subject: Re: [RFC PATCH 0/3] kvm/arm: New VMID allocator based on asid(2nd approach) In-Reply-To: References: <20210506165232.1969-1-shameerali.kolothum.thodi@huawei.com> 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: 62.31.163.78 X-SA-Exim-Rcpt-To: shameerali.kolothum.thodi@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, jean-philippe@linaro.org, Alexandru.Elisei@arm.com, linuxarm@huawei.com 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-20210604_065445_467864_618E3AD5 X-CRM114-Status: GOOD ( 26.57 ) 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 Fri, 04 Jun 2021 09:13:10 +0100, Shameerali Kolothum Thodi wrote: > > Hi, > > > -----Original Message----- > > From: Shameerali Kolothum Thodi > > Sent: 06 May 2021 17:52 > > To: linux-arm-kernel@lists.infradead.org; kvmarm@lists.cs.columbia.edu; > > linux-kernel@vger.kernel.org > > Cc: maz@kernel.org; will@kernel.org; catalin.marinas@arm.com; > > james.morse@arm.com; julien.thierry.kdev@gmail.com; > > suzuki.poulose@arm.com; jean-philippe@linaro.org; Linuxarm > > > > Subject: [RFC PATCH 0/3] kvm/arm: New VMID allocator based on asid(2nd > > approach) > > > > This is based on a suggestion from Will [0] to try out the asid > > based kvm vmid solution as a separate VMID allocator instead of > > the shared lib approach attempted in v4[1]. > > > > The idea is to compare both the approaches and see whether the > > shared lib solution with callbacks make sense or not. > > A gentle ping on this. Please take a look and let me know. I had a look and I don't overly dislike it. I'd like to see the code without the pinned stuff though, at least to ease the reviewing. I haven't tested it in anger, but I have pushed the rebased code at [1] as it really didn't apply to 5.13-rc4. One thing I'm a bit worried about is that we so far relied on VMID 0 never being allocated to a guest, which is now crucial for protected KVM. I can't really convince myself that this can never happen with this. Plus, I've found this nugget: What is this "- 2"? My hunch is that it should really be "- 1" as VMID 0 is reserved, and we have no equivalent of KPTI for S2. M. [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/mmu/vmid -- 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