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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB5DFC77B76 for ; Wed, 12 Apr 2023 08:40:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230400AbjDLIku (ORCPT ); Wed, 12 Apr 2023 04:40:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230150AbjDLIjn (ORCPT ); Wed, 12 Apr 2023 04:39:43 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3024E65 for ; Wed, 12 Apr 2023 01:38:58 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1B3B36300A for ; Wed, 12 Apr 2023 08:37:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C9E5C433EF; Wed, 12 Apr 2023 08:37:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1681288645; bh=Iaujq5ZepP0bJdDw1IZo/f6laXPJ0p0ecE72PG18934=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tKiFjYoZWwtCwiN0DLde9EPobIDvwE4gIZNCOH+O6W1lRR4IJ0qYXU58FyGrgN0C5 FoAncWCrqO0sxVq1EkCtIXJUHiXysSx9Fv8xtQ2s5TppCBfPsQX6aPn8z0zIk+48Zw GZnqsdTn5ePenRLKX6+xi1aelP1izlQRPn7d/4ec= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nico Boehr , Janosch Frank , Christian Borntraeger , Sasha Levin Subject: [PATCH 5.15 27/93] KVM: s390: pv: fix external interruption loop not always detected Date: Wed, 12 Apr 2023 10:33:28 +0200 Message-Id: <20230412082824.213300033@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230412082823.045155996@linuxfoundation.org> References: <20230412082823.045155996@linuxfoundation.org> User-Agent: quilt/0.67 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: Nico Boehr [ Upstream commit 21f27df854008b86349a203bf97fef79bb11f53e ] To determine whether the guest has caused an external interruption loop upon code 20 (external interrupt) intercepts, the ext_new_psw needs to be inspected to see whether external interrupts are enabled. Under non-PV, ext_new_psw can simply be taken from guest lowcore. Under PV, KVM can only access the encrypted guest lowcore and hence the ext_new_psw must not be taken from guest lowcore. handle_external_interrupt() incorrectly did that and hence was not able to reliably tell whether an external interruption loop is happening or not. False negatives cause spurious failures of my kvm-unit-test for extint loops[1] under PV. Since code 20 is only caused under PV if and only if the guest's ext_new_psw is enabled for external interrupts, false positive detection of a external interruption loop can not happen. Fix this issue by instead looking at the guest PSW in the state description. Since the PSW swap for external interrupt is done by the ultravisor before the intercept is caused, this reliably tells whether the guest is enabled for external interrupts in the ext_new_psw. Also update the comments to explain better what is happening. [1] https://lore.kernel.org/kvm/20220812062151.1980937-4-nrb@linux.ibm.com/ Signed-off-by: Nico Boehr Reviewed-by: Janosch Frank Reviewed-by: Christian Borntraeger Fixes: 201ae986ead7 ("KVM: s390: protvirt: Implement interrupt injection") Link: https://lore.kernel.org/r/20230213085520.100756-2-nrb@linux.ibm.com Message-Id: <20230213085520.100756-2-nrb@linux.ibm.com> Signed-off-by: Janosch Frank Signed-off-by: Sasha Levin --- arch/s390/kvm/intercept.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c index 8ca301f49b305..aeb0e0865e890 100644 --- a/arch/s390/kvm/intercept.c +++ b/arch/s390/kvm/intercept.c @@ -271,10 +271,18 @@ static int handle_prog(struct kvm_vcpu *vcpu) * handle_external_interrupt - used for external interruption interceptions * @vcpu: virtual cpu * - * This interception only occurs if the CPUSTAT_EXT_INT bit was set, or if - * the new PSW does not have external interrupts disabled. In the first case, - * we've got to deliver the interrupt manually, and in the second case, we - * drop to userspace to handle the situation there. + * This interception occurs if: + * - the CPUSTAT_EXT_INT bit was already set when the external interrupt + * occurred. In this case, the interrupt needs to be injected manually to + * preserve interrupt priority. + * - the external new PSW has external interrupts enabled, which will cause an + * interruption loop. We drop to userspace in this case. + * + * The latter case can be detected by inspecting the external mask bit in the + * external new psw. + * + * Under PV, only the latter case can occur, since interrupt priorities are + * handled in the ultravisor. */ static int handle_external_interrupt(struct kvm_vcpu *vcpu) { @@ -285,10 +293,18 @@ static int handle_external_interrupt(struct kvm_vcpu *vcpu) vcpu->stat.exit_external_interrupt++; - rc = read_guest_lc(vcpu, __LC_EXT_NEW_PSW, &newpsw, sizeof(psw_t)); - if (rc) - return rc; - /* We can not handle clock comparator or timer interrupt with bad PSW */ + if (kvm_s390_pv_cpu_is_protected(vcpu)) { + newpsw = vcpu->arch.sie_block->gpsw; + } else { + rc = read_guest_lc(vcpu, __LC_EXT_NEW_PSW, &newpsw, sizeof(psw_t)); + if (rc) + return rc; + } + + /* + * Clock comparator or timer interrupt with external interrupt enabled + * will cause interrupt loop. Drop to userspace. + */ if ((eic == EXT_IRQ_CLK_COMP || eic == EXT_IRQ_CPU_TIMER) && (newpsw.mask & PSW_MASK_EXT)) return -EOPNOTSUPP; -- 2.39.2