From patchwork Fri Jul 24 14:35:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 11683445 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7379C138A for ; Fri, 24 Jul 2020 14:37:07 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4C5DB2065C for ; Fri, 24 Jul 2020 14:37:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ewbOQhBB"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="qTwSG62o" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C5DB2065C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5OhbQfPrG2FH6g2arANm0h0RHflD1Mjy7qBMLmWGj6Y=; b=ewbOQhBBPAjLDACSxdqB5O8X9 bOYepC/wcbg1MBqbagiRR5C6X6cwkJqDfDL1hjMVbjIkbt5mpYGRmbyi6fHQTGsXCDFJGwqjOcQQV iYH7g3cTMfvGEmoUih6jAWWGkR+PfBsZJeXvKsZLa2DaCu1khRLHP2cuR6uEAFTloLqbVemSnPEIM UIiVbfvvelRU+hpXa87on1sDYhzUkP0gDnXONlgHQuZY7kGPnKRro0lWMK51fiWw5d6o6xd0HDQwa rMzZPpXGU9eL4iYmi9T87MdZQl4OpRS21znrwlkv3OVx8GdE8UuwtIxVTAH3/E7hoWyQrCDZDx80u TWgUOmNbQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyynB-0003Dl-En; Fri, 24 Jul 2020 14:35:21 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyyn5-0003Be-8J for linux-arm-kernel@lists.infradead.org; Fri, 24 Jul 2020 14:35:16 +0000 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5157D20714; Fri, 24 Jul 2020 14:35:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595601314; bh=4LRg3VE6PVsumxNfed/x5MvUvbAKTRm7x3AQ3dM6Qg4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qTwSG62oN3ulpiaV7VULoi7GrB5vYx5E5xCY7JiMyiyzb30N5XwIu7vTD8ZMuAH0d 366XqaLlIoadq6EhNgruHzbVUEdQ6YdC7fD2gWZrXXlZKOixKxhumcND6ubHwOE+N1 srXcPf6RyLdsYDOgQKoPnGZ0L62tPtAjHt+vDjQs= From: Will Deacon To: kvmarm@lists.cs.columbia.edu Subject: [PATCH 1/7] KVM: arm64: Update comment when skipping guest MMIO access instruction Date: Fri, 24 Jul 2020 15:35:00 +0100 Message-Id: <20200724143506.17772-2-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200724143506.17772-1-will@kernel.org> References: <20200724143506.17772-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200724_103515_395827_DA4FC14A X-CRM114-Status: GOOD ( 12.03 ) X-Spam-Score: -5.2 (-----) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-5.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Quentin Perret , kernel-team@android.com, Suzuki Poulose , James Morse , Marc Zyngier , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org If a 32-bit guest accesses MMIO using a 16-bit Thumb-2 instruction that is reported to the hypervisor without a valid syndrom (for example, because of the addressing mode), then we may hand off the fault to userspace. When resuming the guest, we unconditionally advance the PC by 4 bytes, since ESR_EL2.IL is always 1 for data aborts generated without a valid syndrome. This is a bit rubbish, but it's also difficult to see how we can fix it without potentially introducing regressions in userspace MMIO fault handling. Update the comment when skipping a guest MMIO access instruction so that this corner case is at least written down. Cc: Marc Zyngier Cc: Quentin Perret Signed-off-by: Will Deacon --- arch/arm64/kvm/mmio.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c index 4e0366759726..b54ea5aa6c06 100644 --- a/arch/arm64/kvm/mmio.c +++ b/arch/arm64/kvm/mmio.c @@ -113,6 +113,13 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run) /* * The MMIO instruction is emulated and should not be re-executed * in the guest. + * + * Note: If user space handled the emulation because the abort + * symdrome information was not valid (ISV set in the ESR), then + * this will assume that the faulting instruction was 32-bit. + * If the faulting instruction was a 16-bit Thumb instruction, + * then userspace would need to rewind the PC by 2 bytes prior to + * resuming the vCPU (yuck!). */ kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));