linux-kernel - [RFC PATCH 06/23] x86/ioapic: Add support for IRQCHIP_CAN_DELIVER_AS

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Message-Id: <1528851463-21140-7-git-send-email-ricardo.neri-calderon@linux.intel.com>
Date:   Tue, 12 Jun 2018 17:57:26 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Andi Kleen <andi.kleen@...el.com>, Ashok Raj <ashok.raj@...el.com>,
        Borislav Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>, x86@...nel.org,
        sparclinux@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...el.com>,
        Juergen Gross <jgross@...e.com>, Baoquan He <bhe@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Dou Liyang <douly.fnst@...fujitsu.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        iommu@...ts.linux-foundation.org
Subject: [RFC PATCH 06/23] x86/ioapic: Add support for IRQCHIP_CAN_DELIVER_AS_NMI with interrupt remapping

Even though there is a delivery mode field at the entries of an IO APIC's
redirection table, the documentation of the majority of the IO APICs
explicitly states that interrupt delivery as non-maskable is not supported.
Thus,

However, when using an IO APIC in combination with the Intel VT-d interrupt
remapping functionality, the delivery of the interrupt to the CPU is
handled by the remapping hardware. In such a case, the interrupt can be
delivered as non maskable.

Thus, add the IRQCHIP_CAN_DELIVER_AS_NMI flag only when used in combination
with interrupt remapping.

Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Andi Kleen <andi.kleen@...el.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Jacob Pan <jacob.jun.pan@...el.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Baoquan He <bhe@...hat.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Dou Liyang <douly.fnst@...fujitsu.com>
Cc: Jan Kiszka <jan.kiszka@...mens.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@...el.com>
Cc: x86@...nel.org
Cc: iommu@...ts.linux-foundation.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
---
 arch/x86/kernel/apic/io_apic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 10a20f8..39de91b 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1911,7 +1911,8 @@ static struct irq_chip ioapic_ir_chip __read_mostly = {
 	.irq_eoi		= ioapic_ir_ack_level,
 	.irq_set_affinity	= ioapic_set_affinity,
 	.irq_retrigger		= irq_chip_retrigger_hierarchy,
-	.flags			= IRQCHIP_SKIP_SET_WAKE,
+	.flags			= IRQCHIP_SKIP_SET_WAKE |
+				  IRQCHIP_CAN_DELIVER_AS_NMI,
 };
 
 static inline void init_IO_APIC_traps(void)
-- 
2.7.4