Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
From:   Jan Kiszka <jan.kiszka@siemens.com>
Subject: x86: Spurious vectors not handled robustly
Message-ID: <e525108f-3749-4e1d-1ac2-0d0a2655f15f@siemens.com>
Date:   Mon, 24 Jun 2019 12:00:00 +0200
User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12)
 Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi all,

probably since "x86: Avoid building unused IRQ entry stubs" (2414e021ac8d), the 
kernel can no longer tell spurious IRQs by the APIC apart from spuriously 
triggered unused vectors. We've managed to trigger such a cause with the 
Jailhouse hypervisor (incorrectly injected MANAGED_IRQ_SHUTDOWN_VECTOR), and the 
result was not only a misreport of the vector number (0xff instead of 0xef - 
took me a while...), but also stalled interrupts of equal and lower priority 
because a spurious interrupt is not (and must not be) acknowledged.

How to address that best? I would say we should at least have separate entry 
paths for APIC interrupt vs. vectors, to improve robustness in the faulty case.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux