From patchwork Tue Jul 21 18:37:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: WANG Xuerui X-Patchwork-Id: 11676411 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 F347F13B6 for ; Tue, 21 Jul 2020 18:37:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D780620717 for ; Tue, 21 Jul 2020 18:37:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=xen0n.name header.i=@xen0n.name header.b="VSvHqnaO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730010AbgGUShr (ORCPT ); Tue, 21 Jul 2020 14:37:47 -0400 Received: from [115.28.160.31] ([115.28.160.31]:56240 "EHLO mailbox.box.xen0n.name" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1726658AbgGUShr (ORCPT ); Tue, 21 Jul 2020 14:37:47 -0400 Received: from ld50.lan (unknown [112.65.61.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mailbox.box.xen0n.name (Postfix) with ESMTPSA id A0EAE60132; Wed, 22 Jul 2020 02:37:44 +0800 (CST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=xen0n.name; s=mail; t=1595356664; bh=y5RvLkZ8FlzIOqJPqiqctLeMfbvKvirMnauCtWlPXoM=; h=From:To:Cc:Subject:Date:From; b=VSvHqnaOt0BoUOjnvG9GZNXCQhaHe3aywWWMUT3OLe0V5n/aJ/nAom0U9brH9A0WZ OQE53u67vboYZqe4jjYqkvJnCDvfG+YnzqlF6yWhCazvmtsejykO2rANGhwSdVWn7a vWpk9/umvMOAUBD2kyaWG08v8biiPbHxgObU+0gg= From: WANG Xuerui To: linux-mips@vger.kernel.org Cc: WANG Xuerui Subject: [PATCH v2 0/3] Refactor FTLBPar exception handling and add GSExc handler Date: Wed, 22 Jul 2020 02:37:36 +0800 Message-Id: <20200721183739.1410221-1-git@xen0n.name> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org It was found that some undocumented unprivileged instructions could crash the kernel with a "FTLB parity error" on Loongson-3A4000, but the error registers were garbage: [ 896.970419] FTLB error exception, cp0_ecc=0x00000002: [ 896.975446] cp0_errorepc == ffffffffffffffff [ 896.979755] c0_cacheerr == 00000000 [ 896.983277] Decoded c0_cacheerr: primary cache fault in insn reference. [ 896.989963] Cache error exception: [ 896.993396] cp0_errorepc == ffffffffffffffff [ 896.997707] c0_cacheerr == 00000000 [ 897.001228] Decoded c0_cacheerr: primary cache fault in insn reference. [ 897.007916] Error bits: [ 897.010467] IDX: 0x00000000 [ 897.013284] Kernel panic - not syncing: Can't handle the cache error! [ 897.019807] ---[ end Kernel panic - not syncing: Can't handle the cache error! ]--- Turns out the FTLBPar exception code is actually implementation-specific. On Loongson cores the exception is "GSExc" instead, and is non-fatal in Loongson's linux-3.10 fork. So we dynamically register the correct handler for the exception, and do not panic on the specific undocumented case. P.S. There is not much space left in the cpuinfo_mips.options flag. We should consider moving to something like x86's feature flags that is extensible. v2: - Removed stray GSExc logic in cpu_probe_legacy, pointed out by Huacai WANG Xuerui (3): MIPS: only register FTLBPar exception handler for supported models MIPS: add definitions for Loongson-specific CP0.Diag1 register MIPS: handle Loongson-specific GSExc exception arch/mips/include/asm/cpu-features.h | 10 ++++++++ arch/mips/include/asm/cpu.h | 2 ++ arch/mips/include/asm/mipsregs.h | 11 ++++++++ arch/mips/kernel/cpu-probe.c | 16 ++++++++++++ arch/mips/kernel/genex.S | 7 +++++ arch/mips/kernel/traps.c | 38 +++++++++++++++++++++++++++- 6 files changed, 83 insertions(+), 1 deletion(-)