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=-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 34E13C2D0D2 for ; Wed, 12 May 2021 17:02:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01CFC613BC for ; Wed, 12 May 2021 17:02:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238082AbhELRDd (ORCPT ); Wed, 12 May 2021 13:03:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:35834 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244287AbhELQmv (ORCPT ); Wed, 12 May 2021 12:42:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 58DC461D42; Wed, 12 May 2021 16:12:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620835937; bh=PWaRI9EWYhzIGjtpdkfvAHCGvfDcD6puNDKoN9z9ALc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bLH8ee7MuiqnutFrjX9AewsyyiPWoKUxb28C8dXOdk9ENpJTjBW0yFTjruGrupL3z RoDc5OJLn54NT78Ds42teYNaElOpik3XHZx0zC6jUD+kw2C5fUA33TFX9mDD2jFT9f ntfx4lDnLnxGZk8wqXTUvTTZ9KnjY6zojuMs0NvA= 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 5.12 544/677] KVM: PPC: Book3S HV P9: Restore host CTRL SPR after guest exit Date: Wed, 12 May 2021 16:49:50 +0200 Message-Id: <20210512144855.443743709@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210512144837.204217980@linuxfoundation.org> References: <20210512144837.204217980@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 13bad6bf4c95..208a053c9adf 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3728,7 +3728,10 @@ static 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); -- 2.30.2