From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756870AbdEHT7r (ORCPT ); Mon, 8 May 2017 15:59:47 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:34332 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754550AbdEHT7o (ORCPT ); Mon, 8 May 2017 15:59:44 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 5ECB56028F Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=tbaicar@codeaurora.org Subject: Re: [PATCH V15 06/11] acpi: apei: handle SEA notification type for ARMv8 To: James Morse Cc: christoffer.dall@linaro.org, marc.zyngier@arm.com, pbonzini@redhat.com, rkrcmar@redhat.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, rjw@rjwysocki.net, lenb@kernel.org, matt@codeblueprint.co.uk, robert.moore@intel.com, lv.zheng@intel.com, nkaje@codeaurora.org, zjzhang@codeaurora.org, mark.rutland@arm.com, akpm@linux-foundation.org, eun.taik.lee@samsung.com, sandeepa.s.prabhu@gmail.com, labbott@redhat.com, shijie.huang@arm.com, rruigrok@codeaurora.org, paul.gortmaker@windriver.com, tn@semihalf.com, fu.wei@linaro.org, rostedt@goodmis.org, bristot@redhat.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-efi@vger.kernel.org, devel@acpica.org, Suzuki.Poulose@arm.com, punit.agrawal@arm.com, astone@redhat.com, harba@codeaurora.org, hanjun.guo@linaro.org, john.garry@huawei.com, shiju.jose@huawei.com, joe@perches.com, bp@alien8.de, rafael@kernel.org, tony.luck@intel.com, gengdongjiu@huawei.com, xiexiuqi@huawei.com References: <1492556723-9189-1-git-send-email-tbaicar@codeaurora.org> <1492556723-9189-7-git-send-email-tbaicar@codeaurora.org> <5910AAB8.8070703@arm.com> From: "Baicar, Tyler" Message-ID: <9e26f779-5eae-2558-6045-10c1afde9bf2@codeaurora.org> Date: Mon, 8 May 2017 13:59:37 -0600 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <5910AAB8.8070703@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/8/2017 11:28 AM, James Morse wrote: > Hi Tyler, > > On 19/04/17 00:05, Tyler Baicar wrote: >> ARM APEI extension proposal added SEA (Synchronous External Abort) >> notification type for ARMv8. >> Add a new GHES error source handling function for SEA. If an error >> source's notification type is SEA, then this function can be registered >> into the SEA exception handler. That way GHES will parse and report >> SEA exceptions when they occur. >> An SEA can interrupt code that had interrupts masked and is treated as >> an NMI. To aid this the page of address space for mapping APEI buffers >> while in_nmi() is always reserved, and ghes_ioremap_pfn_nmi() is >> changed to use the helper methods to find the prot_t to map with in >> the same way as ghes_ioremap_pfn_irq(). >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index b74d8b7..10013ff 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -518,6 +520,17 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) >> pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n", >> inf->name, esr, addr); >> >> + /* >> + * Synchronous aborts may interrupt code which had interrupts masked. >> + * Before calling out into the wider kernel tell the interested >> + * subsystems. >> + */ >> + if (IS_ENABLED(CONFIG_ACPI_APEI_SEA)) { >> + nmi_enter(); >> + ghes_notify_sea(); >> + nmi_exit(); >> + } >> + >> info.si_signo = SIGBUS; >> info.si_errno = 0; >> info.si_code = 0; > > I was tidying up the masking/unmasking in entry.S, something I wasn't aware of > that leads to a bug: > entry.S will unmask interrupts for instruction/data aborts that came from a > context with interrupts enabled. This makes sense for get_user() and friends... > For do_sea() we pull nmi_enter() as this can interrupt interrupts-masked code, > such as APEI, but if we end up in here with interrupts unmasked we can take an > IRQ from this 'NMI' context, which will inherit the in_nmi() and could lead to > the deadlock we were originally trying to avoid. > > Teaching entry.S to spot external aborts is messy. I think the two choices are > to either mask interrupts when calling nmi_enter() (as these things should be > mutually exclusive), or to conditionally call nmi_enter() based on > interrupts_enabled(regs). I prefer the second one as it matches the notify_sea() > while interruptible that happens when KVM takes one of these. Hello James, So it would need to be like this? if(interrupts_enabled(regs)) nmi_enter(); ghes_notify_sea(); if(interrupts_enabled(regs)) nmi_exit(); Thanks, Tyler -- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.