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 X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F5C7C43219 for ; Fri, 24 Sep 2021 08:25:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 657AA61214 for ; Fri, 24 Sep 2021 08:25:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244633AbhIXI1b (ORCPT ); Fri, 24 Sep 2021 04:27:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:34316 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244734AbhIXI10 (ORCPT ); Fri, 24 Sep 2021 04:27:26 -0400 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 589C861241; Fri, 24 Sep 2021 08:25:53 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.lan) 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 1mTgWl-00ChmL-Nu; Fri, 24 Sep 2021 09:25:51 +0100 From: Marc Zyngier To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: James Morse , Suzuki K Poulose , Alexandru Elisei , Eric Auger , Christoffer Dall , kernel-team@android.com Subject: [PATCH 2/5] KVM: arm64: Work around GICv3 locally generated SErrors Date: Fri, 24 Sep 2021 09:25:39 +0100 Message-Id: <20210924082542.2766170-3-maz@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210924082542.2766170-1-maz@kernel.org> References: <20210924082542.2766170-1-maz@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, suzuki.poulose@arm.com, alexandru.elisei@arm.com, eric.auger@redhat.com, christoffer.dall@arm.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The infamous M1 has a feature nobody else ever implemented, in the form of the "GIC locally generated SError interrupts", also known as SEIS for short. These SErrors are generated when a guest does something that violates the GIC state machine. It would have been simpler to just *ignore* the damned thing, but that's not what this HW does. Oh well. This part of of the architecture is also amazingly under-specified. There is a whole 10 lines that describe the feature in a spec that is 930 pages long, and some of these lines are factually wrong. Oh, and it is deprecated, so the insentive to clarify it is low. Now, the spec says that this should be a *virtual* SError when HCR_EL2.AMO is set. As it turns out, that's not always the case on this CPU, and the SError sometimes fires on the host as a physical SError. Goodbye, cruel world. This clearly is a HW bug, and it means that a guest can easily take the host down, on demand. Thankfully, we have seen systems that were just as broken in the past, and we have the perfect vaccine for it. Apple M1, please meet the Cavium ThunderX workaround. All your GIC accesses will be trapped, sanitised, and emulated. Only the signalling aspect of the HW will be used. It won't be super speedy, but it will at least be safe. You're most welcome. Given that this has only ever been seen on this single implementation, that the spec is unclear at best and that we cannot trust it to ever be implemented correctly, gate the workaround solely on ICH_VTR_EL2.SEIS being set. Signed-off-by: Marc Zyngier --- arch/arm64/kvm/vgic/vgic-v3.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c index 21a6207fb2ee..ae59e2580bf5 100644 --- a/arch/arm64/kvm/vgic/vgic-v3.c +++ b/arch/arm64/kvm/vgic/vgic-v3.c @@ -671,6 +671,14 @@ int vgic_v3_probe(const struct gic_kvm_info *info) group1_trap = true; } + if (kvm_vgic_global_state.ich_vtr_el2 & ICH_VTR_SEIS_MASK) { + kvm_info("GICv3 with locally generated SEI\n"); + + group0_trap = true; + group1_trap = true; + common_trap = true; + } + if (group0_trap || group1_trap || common_trap) { kvm_info("GICv3 sysreg trapping enabled ([%s%s%s], reduced performance)\n", group0_trap ? "G0" : "", -- 2.30.2