From patchwork Wed Mar 11 14:44:38 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Hogan X-Patchwork-Id: 5986071 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id C91879F380 for ; Wed, 11 Mar 2015 14:48:21 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id DD2552041F for ; Wed, 11 Mar 2015 14:48:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D900A20377 for ; Wed, 11 Mar 2015 14:48:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753418AbbCKOsM (ORCPT ); Wed, 11 Mar 2015 10:48:12 -0400 Received: from mailapp01.imgtec.com ([195.59.15.196]:22609 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752907AbbCKOsH (ORCPT ); Wed, 11 Mar 2015 10:48:07 -0400 Received: from KLMAIL01.kl.imgtec.org (unknown [192.168.5.35]) by Websense Email Security Gateway with ESMTPS id 190723FDFAEE0; Wed, 11 Mar 2015 14:48:03 +0000 (GMT) Received: from LEMAIL01.le.imgtec.org (192.168.152.62) by KLMAIL01.kl.imgtec.org (192.168.5.35) with Microsoft SMTP Server (TLS) id 14.3.195.1; Wed, 11 Mar 2015 14:48:05 +0000 Received: from jhogan-linux.le.imgtec.org (192.168.154.110) by LEMAIL01.le.imgtec.org (192.168.152.62) with Microsoft SMTP Server (TLS) id 14.3.210.2; Wed, 11 Mar 2015 14:48:04 +0000 From: James Hogan To: Paolo Bonzini , , CC: James Hogan , Ralf Baechle , Paul Burton , Gleb Natapov Subject: [PATCH 02/20] MIPS: Clear [MSA]FPE CSR.Cause after notify_die() Date: Wed, 11 Mar 2015 14:44:38 +0000 Message-ID: <1426085096-12932-3-git-send-email-james.hogan@imgtec.com> X-Mailer: git-send-email 2.0.5 In-Reply-To: <1426085096-12932-1-git-send-email-james.hogan@imgtec.com> References: <1426085096-12932-1-git-send-email-james.hogan@imgtec.com> MIME-Version: 1.0 X-Originating-IP: [192.168.154.110] Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When handling floating point exceptions (FPEs) and MSA FPEs the Cause bits of the appropriate control and status register (FCSR for FPEs and MSACSR for MSA FPEs) are read and cleared before enabling interrupts, presumably so that it doesn't have to go through the pain of restoring those bits if the process is pre-empted, since writing those bits would cause another immediate exception while still in the kernel. The bits aren't normally ever restored again, since userland never expects to see them set. However for virtualisation it is necessary for the kernel to be able to restore these Cause bits, as the guest may have been interrupted in an FP exception handler but before it could read the Cause bits. This can be done by registering a die notifier, to get notified of the exception when such a value is restored, and if the PC was at the instruction which is used to restore the guest state, the handler can step over it and continue execution. The Cause bits can then remain set without causing further exceptions. For this to work safely a few changes are made: - __build_clear_fpe and __build_clear_msa_fpe no longer clear the Cause bits, and now return from exception level with interrupts disabled instead of enabled. - do_fpe() now clears the Cause bits and enables interrupts after notify_die() is called, so that the notifier can chose to return from exception without this happening. - do_msa_fpe() acts similarly, but now actually makes use of the second argument (msacsr) and calls notify_die() with the new DIE_MSAFP, allowing die notifiers to be informed of MSA FPEs too. Signed-off-by: James Hogan Cc: Ralf Baechle Cc: Paul Burton Cc: Paolo Bonzini Cc: Gleb Natapov Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Acked-by: Ralf Baechle --- arch/mips/include/asm/kdebug.h | 3 ++- arch/mips/kernel/genex.S | 14 ++++---------- arch/mips/kernel/traps.c | 16 +++++++++++++++- 3 files changed, 21 insertions(+), 12 deletions(-) diff --git a/arch/mips/include/asm/kdebug.h b/arch/mips/include/asm/kdebug.h index 6a9af5fcb5d7..cba22ab7ad4d 100644 --- a/arch/mips/include/asm/kdebug.h +++ b/arch/mips/include/asm/kdebug.h @@ -10,7 +10,8 @@ enum die_val { DIE_RI, DIE_PAGE_FAULT, DIE_BREAK, - DIE_SSTEPBP + DIE_SSTEPBP, + DIE_MSAFP }; #endif /* _ASM_MIPS_KDEBUG_H */ diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S index 86e22422d08c..af42e7003f12 100644 --- a/arch/mips/kernel/genex.S +++ b/arch/mips/kernel/genex.S @@ -360,21 +360,15 @@ NESTED(nmi_handler, PT_SIZE, sp) .set mips1 SET_HARDFLOAT cfc1 a1, fcr31 - li a2, ~(0x3f << 12) - and a2, a1 - ctc1 a2, fcr31 .set pop - TRACE_IRQS_ON - STI + CLI + TRACE_IRQS_OFF .endm .macro __build_clear_msa_fpe _cfcmsa a1, MSA_CSR - li a2, ~(0x3f << 12) - and a1, a1, a2 - _ctcmsa MSA_CSR, a1 - TRACE_IRQS_ON - STI + CLI + TRACE_IRQS_OFF .endm .macro __build_clear_ade diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index 8943ebe4d154..5b4d711f878d 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -788,6 +788,11 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31) if (notify_die(DIE_FP, "FP exception", regs, 0, regs_to_trapnr(regs), SIGFPE) == NOTIFY_STOP) goto out; + + /* Clear FCSR.Cause before enabling interrupts */ + write_32bit_cp1_register(CP1_STATUS, fcr31 & ~FPU_CSR_ALL_X); + local_irq_enable(); + die_if_kernel("FP exception in kernel code", regs); if (fcr31 & FPU_CSR_UNI_X) { @@ -1393,13 +1398,22 @@ out: exception_exit(prev_state); } -asmlinkage void do_msa_fpe(struct pt_regs *regs) +asmlinkage void do_msa_fpe(struct pt_regs *regs, unsigned int msacsr) { enum ctx_state prev_state; prev_state = exception_enter(); + if (notify_die(DIE_MSAFP, "MSA FP exception", regs, 0, + regs_to_trapnr(regs), SIGFPE) == NOTIFY_STOP) + goto out; + + /* Clear MSACSR.Cause before enabling interrupts */ + write_msa_csr(msacsr & ~MSA_CSR_CAUSEF); + local_irq_enable(); + die_if_kernel("do_msa_fpe invoked from kernel context!", regs); force_sig(SIGFPE, current); +out: exception_exit(prev_state); }