From nobody Wed Feb 11 02:33:17 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1511326312527408.21284192048165; Tue, 21 Nov 2017 20:51:52 -0800 (PST) Received: from localhost ([::1]:37845 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eHN0k-0000I9-UH for importer@patchew.org; Tue, 21 Nov 2017 23:51:46 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60343) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eHMxU-0005vS-1R for qemu-devel@nongnu.org; Tue, 21 Nov 2017 23:48:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eHMxT-00038A-3p for qemu-devel@nongnu.org; Tue, 21 Nov 2017 23:48:24 -0500 Received: from ozlabs.org ([2401:3900:2:1::2]:34049) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eHMxS-000363-CI; Tue, 21 Nov 2017 23:48:22 -0500 Received: by ozlabs.org (Postfix, from userid 1007) id 3yhVMP0wpRz9s1h; Wed, 22 Nov 2017 15:48:17 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1511326097; bh=qQlepJEM+GBW2holShDqfC7t/cG2e7LcsVCIUbr63cg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cMJAQ9cKhsPgprfqjVUq0gph06iwnKb8xww30xPOmwrn3kUX/tYD1IstM9/zdQIZ9 ERj2WKGQYILeZpijDwwkOrb6w0zQRzDwRzN+qsKZFhqYxwvDjyteySqGljtk+058nx vRMUfwnkHYCiFDcD2cGwGNkTJhhG0EbP8cnejPhU= From: David Gibson To: peter.maydell@linaro.org Date: Wed, 22 Nov 2017 15:48:14 +1100 Message-Id: <20171122044814.3001-4-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20171122044814.3001-1-david@gibson.dropbear.id.au> References: <20171122044814.3001-1-david@gibson.dropbear.id.au> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2401:3900:2:1::2 Subject: [Qemu-devel] [PULL 3/3] ppc: fix VTB migration X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: lvivier@redhat.com, qemu-devel@nongnu.org, agraf@suse.de, groug@kaod.org, qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Laurent Vivier Migration of a system under stress (for example, with "stress-ng --numa 2") triggers on the destination some kernel watchdog messages like: NMI watchdog: BUG: soft lockup - CPU#0 stuck for 3489660870s! NMI watchdog: BUG: soft lockup - CPU#1 stuck for 3489660884s! This problem appears with the changes introduced by 42043e4 spapr: clock should count only if vm is running I think this commit only triggers the problem. Kernel computes the soft lockup duration using the Virtual Timebase register (VTB), not using the Timebase Register (TBR, the one 42043e4 stops). It appears VTB is not migrated, so this patch adds it in the list of the SPRs to migrate, and fixes the problem. For the migration, I've tested a migration from qemu-2.8.0 and pseries-2.8.0 to a patched master (qemu-2.11.0-rc1). The received VTB is 0 (as is it not initialized by qemu-2.8.0), but the value seems to be ignored by KVM and a non zero VTB is used by the kernel. I have no explanation for that, but as the original problem appears only with SMP system under stress I suspect some problems in KVM (I think because VTB is shared by all threads of a core). Signed-off-by: Laurent Vivier Signed-off-by: David Gibson --- target/ppc/translate_init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c index b9c49c22f2..4e11e6f489 100644 --- a/target/ppc/translate_init.c +++ b/target/ppc/translate_init.c @@ -8081,10 +8081,10 @@ static void gen_spr_power8_ebb(CPUPPCState *env) /* Virtual Time Base */ static void gen_spr_vtb(CPUPPCState *env) { - spr_register(env, SPR_VTB, "VTB", + spr_register_kvm(env, SPR_VTB, "VTB", SPR_NOACCESS, SPR_NOACCESS, &spr_read_tbl, SPR_NOACCESS, - 0x00000000); + KVM_REG_PPC_VTB, 0x00000000); } =20 static void gen_spr_power8_fscr(CPUPPCState *env) --=20 2.14.3