linux-kernel - [PATCH v2 11/12] x86/jailhouse: Wire up IOAPIC for legacy UART ports

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Date:   Mon, 27 Nov 2017 09:11:53 +0100
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        jailhouse-dev@...glegroups.com
Subject: [PATCH v2 11/12] x86/jailhouse: Wire up IOAPIC for legacy UART ports

From: Jan Kiszka <jan.kiszka@...mens.com>

The typical I/O interrupts in non-root cells are MSI-based. However, the
platform UARTs do not support MSI. In order to run a non-root cell that
shall be use one of them, we need to register the standard IOAPIC and
set 1:1 routing for IRQ 3 and 4.

If an IOAPIC is not available, the boot loader clears standard_ioapic in
the setup data, and we skip the registration. If we should not be
allowed to use one of those pins, Jailhouse will simply ignore our
accesses.

Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
 arch/x86/kernel/jailhouse.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c
index c8ee638b6bce..8ff21e1534de 100644
--- a/arch/x86/kernel/jailhouse.c
+++ b/arch/x86/kernel/jailhouse.c
@@ -17,6 +17,7 @@
 #include <asm/cpu.h>
 #include <asm/hypervisor.h>
 #include <asm/i8259.h>
+#include <asm/irqdomain.h>
 #include <asm/reboot.h>
 #include <asm/setup.h>
 
@@ -54,6 +55,15 @@ static unsigned long jailhouse_get_tsc(void)
 
 static void __init jailhouse_get_smp_config(unsigned int early)
 {
+	struct ioapic_domain_cfg ioapic_cfg = {
+		.type = IOAPIC_DOMAIN_STRICT,
+		.ops = &mp_ioapic_irqdomain_ops,
+	};
+	struct mpc_intsrc mp_irq = {
+		.type = MP_INTSRC,
+		.irqtype = mp_INT,
+		.irqflag = MP_IRQPOL_ACTIVE_HIGH | MP_IRQTRIG_EDGE,
+	};
 	unsigned int cpu;
 
 	if (x2apic_enabled()) {
@@ -79,6 +89,17 @@ static void __init jailhouse_get_smp_config(unsigned int early)
 	}
 
 	smp_found_config = 1;
+
+	if (setup_data.standard_ioapic) {
+		mp_register_ioapic(0, 0xfec00000, gsi_top, &ioapic_cfg);
+
+		/* Register 1:1 mapping for legacy UART IRQs 3 and 4 */
+		mp_irq.srcbusirq = mp_irq.dstirq = 3;
+		mp_save_irq(&mp_irq);
+
+		mp_irq.srcbusirq = mp_irq.dstirq = 4;
+		mp_save_irq(&mp_irq);
+	}
 }
 
 static void jailhouse_no_restart(void)
-- 
2.12.3