From patchwork Wed May 12 14:49:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 437149 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 20F93C43460 for ; Wed, 12 May 2021 15:05:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8AB461948 for ; Wed, 12 May 2021 15:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232876AbhELPGg (ORCPT ); Wed, 12 May 2021 11:06:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:59144 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233408AbhELPFT (ORCPT ); Wed, 12 May 2021 11:05:19 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B51676147F; Wed, 12 May 2021 15:00:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620831619; bh=XwWBhPlLfnjVQSgw2YhUE0NKT+8PxLOb/ix8XFTYz8Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c5jtfmpQ/g3Ac/G4z1r1tYdk16FaHQOUeqicgTsRBqZcpizQXnM+dw7md6ob2QKCx qo0dydTs2LbWbtBOahoR/aQhT3y7fKZFXw+5p6Z7bexgBkDAHYkFQG8x1/SPY83S2C 5SdW1j0PNhCPxbf9LCSVeikaDyK6tjmIQqeLz7uU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nicholas Piggin , Michael Ellerman , Sasha Levin Subject: [PATCH 5.4 191/244] KVM: PPC: Book3S HV P9: Restore host CTRL SPR after guest exit Date: Wed, 12 May 2021 16:49:22 +0200 Message-Id: <20210512144749.110034404@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210512144743.039977287@linuxfoundation.org> References: <20210512144743.039977287@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Nicholas Piggin [ Upstream commit 5088eb4092df12d701af8e0e92860b7186365279 ] The host CTRL (runlatch) value is not restored after guest exit. The host CTRL should always be 1 except in CPU idle code, so this can result in the host running with runlatch clear, and potentially switching to a different vCPU which then runs with runlatch clear as well. This has little effect on P9 machines, CTRL is only responsible for some PMU counter logic in the host and so other than corner cases of software relying on that, or explicitly reading the runlatch value (Linux does not appear to be affected but it's possible non-Linux guests could be), there should be no execution correctness problem, though it could be used as a covert channel between guests. There may be microcontrollers, firmware or monitoring tools that sample the runlatch value out-of-band, however since the register is writable by guests, these values would (should) not be relied upon for correct operation of the host, so suboptimal performance or incorrect reporting should be the worst problem. Fixes: 95a6432ce9038 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests") Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210412014845.1517916-2-npiggin@gmail.com Signed-off-by: Sasha Levin --- arch/powerpc/kvm/book3s_hv.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index dd9b19b1f459..6938b793a015 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3638,7 +3638,10 @@ int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, vcpu->arch.dec_expires = dec + tb; vcpu->cpu = -1; vcpu->arch.thread_cpu = -1; + /* Save guest CTRL register, set runlatch to 1 */ vcpu->arch.ctrl = mfspr(SPRN_CTRLF); + if (!(vcpu->arch.ctrl & 1)) + mtspr(SPRN_CTRLT, vcpu->arch.ctrl | 1); vcpu->arch.iamr = mfspr(SPRN_IAMR); vcpu->arch.pspb = mfspr(SPRN_PSPB);