From patchwork Fri Sep 4 11:24:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andre Przywara X-Patchwork-Id: 264393 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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 C450BC43461 for ; Fri, 4 Sep 2020 11:30:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95F0B206B7 for ; Fri, 4 Sep 2020 11:30:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730157AbgIDLaq (ORCPT ); Fri, 4 Sep 2020 07:30:46 -0400 Received: from foss.arm.com ([217.140.110.172]:48822 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730155AbgIDLYr (ORCPT ); Fri, 4 Sep 2020 07:24:47 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C3C6712FC; Fri, 4 Sep 2020 04:24:45 -0700 (PDT) Received: from donnerap.arm.com (donnerap.cambridge.arm.com [10.1.195.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 01F1D3F71F; Fri, 4 Sep 2020 04:24:44 -0700 (PDT) From: Andre Przywara To: stable@vger.kernel.org Cc: James Morse , Marc Zyngier , Catalin Marinas Subject: [PATCH stable v4.14 2/4] KVM: arm64: Defer guest entry when an asynchronous exception is pending Date: Fri, 4 Sep 2020 12:24:35 +0100 Message-Id: <20200904112437.200212-3-andre.przywara@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200904112437.200212-1-andre.przywara@arm.com> References: <20200904112437.200212-1-andre.przywara@arm.com> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: James Morse commit 5dcd0fdbb492d49dac6bf21c436dfcb5ded0a895 upstream. SError that occur during world-switch's entry to the guest will be accounted to the guest, as the exception is masked until we enter the guest... but we want to attribute the SError as precisely as possible. Reading DISR_EL1 before guest entry requires free registers, and using ESB+DISR_EL1 to consume and read back the ESR would leave KVM holding a host SError... We would rather leave the SError pending and let the host take it once we exit world-switch. To do this, we need to defer guest-entry if an SError is pending. Read the ISR to see if SError (or an IRQ) is pending. If so fake an exit. Place this check between __guest_enter()'s save of the host registers, and restore of the guest's. SError that occur between here and the eret into the guest must have affected the guest's registers, which we can naturally attribute to the guest. The dsb is needed to ensure any previous writes have been done before we read ISR_EL1. On systems without the v8.2 RAS extensions this doesn't give us anything as we can't contain errors, and the ESR bits to describe the severity are all implementation-defined. Replace this with a nop for these systems. v4.14-backport: as this kernel version doesn't have the RAS support at all, remove the RAS alternative. Cc: stable@vger.kernel.org # v4.14 Signed-off-by: James Morse Signed-off-by: Marc Zyngier [ James: Removed v8.2 RAS related barriers ] Signed-off-by: James Morse Signed-off-by: Andre Przywara --- arch/arm64/kvm/hyp/entry.S | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index 76545f95f704..4e0eac361f87 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -17,6 +17,7 @@ #include +#include #include #include #include @@ -62,6 +63,15 @@ ENTRY(__guest_enter) // Store the host regs save_callee_saved_regs x1 + // Now the host state is stored if we have a pending RAS SError it must + // affect the host. If any asynchronous exception is pending we defer + // the guest entry. + mrs x1, isr_el1 + cbz x1, 1f + mov x0, #ARM_EXCEPTION_IRQ + ret + +1: add x18, x0, #VCPU_CONTEXT // Restore guest regs x0-x17