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Thu, 23 Sep 2021 13:11:24 +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 1mTOVU-00BXaa-Cy for linux-arm-kernel@lists.infradead.org; Thu, 23 Sep 2021 13:11:21 +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 0F0786103D; Thu, 23 Sep 2021 13:11:20 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] 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 1mTOVS-00CXQj-2g; Thu, 23 Sep 2021 14:11:18 +0100 Date: Thu, 23 Sep 2021 14:11:17 +0100 Message-ID: <87y27ntp1m.wl-maz@kernel.org> From: Marc Zyngier To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, Quentin Perret , Catalin Marinas , Alexandru Elisei , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH 5/5] KVM: arm64: Disable privileged hypercalls after pKVM finalisation In-Reply-To: <20210923130211.GB15934@willie-the-truck> References: <20210923112256.15767-1-will@kernel.org> <20210923112256.15767-6-will@kernel.org> <87zgs3tpqi.wl-maz@kernel.org> <20210923130211.GB15934@willie-the-truck> 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: 185.219.108.64 X-SA-Exim-Rcpt-To: will@kernel.org, linux-arm-kernel@lists.infradead.org, qperret@google.com, catalin.marinas@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, kvmarm@lists.cs.columbia.edu 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-20210923_061120_500223_DFCFD976 X-CRM114-Status: GOOD ( 24.58 ) 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, 23 Sep 2021 14:02:11 +0100, Will Deacon wrote: > > On Thu, Sep 23, 2021 at 01:56:21PM +0100, Marc Zyngier wrote: > > On Thu, 23 Sep 2021 12:22:56 +0100, > > Will Deacon wrote: [...] > > > static void handle_host_hcall(struct kvm_cpu_context *host_ctxt) > > > { > > > DECLARE_REG(unsigned long, id, host_ctxt, 0); > > > + unsigned long hcall_min = 0; > > > hcall_t hfn; > > > > > > + if (static_branch_unlikely(&kvm_protected_mode_initialized)) > > > + hcall_min = __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize; > > > + > > > id -= KVM_HOST_SMCCC_ID(0); > > > > > > - if (unlikely(id >= ARRAY_SIZE(host_hcall))) > > > + if (unlikely(id < hcall_min || id >= ARRAY_SIZE(host_hcall))) > > > > So I can still issue a pkvm_prot_finalize after finalisation? Seems > > odd. As hcall_min has to be inclusive, you probably want it to be set > > to __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp once protected. > > Yeah, I ended up addresing that one in the previous patch. The problem is > that we need to allow pkvm_prot_finalize to be called on each CPU, so I > think we'd end up having an extra "really finalize damnit!" call to be > issued _once_ after each CPU is done with the finalisation if we want > to lock it down. > > The approach I took instead is to make pkvm_prot_finalize return -EBUSY > if it's called on a CPU where it's already been called. Ah, I see. Serves me right for reading patches out of order. Finalise is of course per-CPU, and the static key global. Epic fail. Probably deserves a comment, because I'm surely going to jump at that again in three months. 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