From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Baicar, Tyler" Subject: Re: [PATCH V15 06/11] acpi: apei: handle SEA notification type for ARMv8 Date: Mon, 8 May 2017 13:59:37 -0600 Message-ID: <9e26f779-5eae-2558-6045-10c1afde9bf2@codeaurora.org> References: <1492556723-9189-1-git-send-email-tbaicar@codeaurora.org> <1492556723-9189-7-git-send-email-tbaicar@codeaurora.org> <5910AAB8.8070703@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5910AAB8.8070703-5wv7dgnIgG8@public.gmane.org> Content-Language: en-US Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: James Morse Cc: christoffer.dall-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, marc.zyngier-5wv7dgnIgG8@public.gmane.org, pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, rkrcmar-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org, catalin.marinas-5wv7dgnIgG8@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org, lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org, robert.moore-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, lv.zheng-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, nkaje-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, zjzhang-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, mark.rutland-5wv7dgnIgG8@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, eun.taik.lee-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org, sandeepa.s.prabhu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, labbott-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, shijie.huang-5wv7dgnIgG8@public.gmane.org, rruigrok-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, paul.gortmaker-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org, tn-nYOzD4b6Jr9Wk0Htik3J/w@public.gmane.org, fu.wei-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, kvmarm-FPEHb7Xf0XXUo1n7N8X6UoWGPAHP3yOg@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devel-E0kO6a4B6psdnm+yROfE0A@public.gmane.org, Suzuki.Po List-Id: kvmarm@lists.cs.columbia.edu 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.