Introduce paravirq irq_domain for interrupts injected by the hypervisor
using Intel VT-x technology. Paravirq irq_domain allows registering
IRQ handlers for these interrupts and avoid emulating an MSI-capable
PCI device by the hypervisor.
Signed-off-by: Alexander Popov <alex.popov@xxxxxxxxx>
---
arch/x86/Kconfig | 8 +++
arch/x86/include/asm/irqdomain.h | 6 ++
arch/x86/include/asm/paravirq.h | 9 +++
arch/x86/kernel/apic/Makefile | 2 +
arch/x86/kernel/apic/paravirq.c | 128 +++++++++++++++++++++++++++++++++++++++
arch/x86/kernel/apic/vector.c | 1 +
6 files changed, 154 insertions(+)
create mode 100644 arch/x86/include/asm/paravirq.h
create mode 100644 arch/x86/kernel/apic/paravirq.c
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5c6e747..209bd88 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -760,6 +760,14 @@ config PARAVIRT_TIME_ACCOUNTING
If in doubt, say N here.
+config X86_PARAVIRQ
+ bool "Enable paravirq irq_domain"
+ depends on PARAVIRT && X86_LOCAL_APIC
+ default n
+ ---help---
+ This option enables paravirq irq_domain for interrupts injected
+ by the hypervisor using Intel VT-x technology.
+
config PARAVIRT_CLOCK
bool
diff --git a/arch/x86/include/asm/irqdomain.h b/arch/x86/include/asm/irqdomain.h
index d26075b..e3192f6 100644
--- a/arch/x86/include/asm/irqdomain.h
+++ b/arch/x86/include/asm/irqdomain.h
@@ -60,4 +60,10 @@ extern void arch_init_htirq_domain(struct irq_domain *domain);
static inline void arch_init_htirq_domain(struct irq_domain *domain) { }
#endif
+#ifdef CONFIG_X86_PARAVIRQ
+extern void arch_init_paravirq_domain(struct irq_domain *domain);
+#else
+static inline void arch_init_paravirq_domain(struct irq_domain *domain) { }
+#endif
+
#endif
diff --git a/arch/x86/include/asm/paravirq.h b/arch/x86/include/asm/paravirq.h
new file mode 100644
index 0000000..a137de2
--- /dev/null
+++ b/arch/x86/include/asm/paravirq.h
@@ -0,0 +1,9 @@
+#ifndef _ASM_X86_PARAVIRQ_H
+#define _ASM_X86_PARAVIRQ_H
+
+int paravirq_init_chip(void (*irq_mask)(struct irq_data *data),
+ void (*irq_unmask)(struct irq_data *data));
+int paravirq_alloc_irq(void);
+void paravirq_free_irq(unsigned int irq);
+
+#endif /* _ASM_X86_PARAVIRQ_H */
diff --git a/arch/x86/kernel/apic/Makefile b/arch/x86/kernel/apic/Makefile
index 8e63ebd..84f9ce0 100644
--- a/arch/x86/kernel/apic/Makefile
+++ b/arch/x86/kernel/apic/Makefile
@@ -28,3 +28,5 @@ obj-$(CONFIG_X86_BIGSMP) += bigsmp_32.o
# For 32bit, probe_32 need to be listed last
obj-$(CONFIG_X86_LOCAL_APIC) += probe_$(BITS).o
+
+obj-$(CONFIG_X86_PARAVIRQ) += paravirq.o
diff --git a/arch/x86/kernel/apic/paravirq.c b/arch/x86/kernel/apic/paravirq.c
new file mode 100644
index 0000000..430b819
--- /dev/null
+++ b/arch/x86/kernel/apic/paravirq.c
@@ -0,0 +1,128 @@
+/*
+ * An irq_domain for interrupts injected by the hypervisor using
+ * Intel VT-x technology.
+ *
+ * Copyright (C) 2016 Alexander Popov <alex.popov@xxxxxxxxx>.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <asm/irqdomain.h>
+#include <asm/paravirq.h>
+
+static struct irq_domain *paravirq_domain;
+
+static struct irq_chip paravirq_chip = {
+ .name = "PARAVIRQ",
+ .irq_ack = irq_chip_ack_parent,
+};
+
+static int paravirq_domain_alloc(struct irq_domain *domain,
+ unsigned int virq, unsigned int nr_irqs, void *arg)
+{
+ int ret = 0;
+
+ BUG_ON(domain != paravirq_domain);
+
+ if (nr_irqs != 1)
+ return -EINVAL;
+
+ ret = irq_domain_set_hwirq_and_chip(paravirq_domain,
+ virq, virq, ¶virq_chip, NULL);
+ if (ret) {
+ pr_warn("setting chip, hwirq for irq %u failed\n", virq);
+ return ret;
+ }
+
+ __irq_set_handler(virq, handle_edge_irq, 0, "edge");
+
+ return 0;
+}
+
+static void paravirq_domain_free(struct irq_domain *domain,
+ unsigned int virq, unsigned int nr_irqs)
+{
+ struct irq_data *irq_data;
+
+ BUG_ON(domain != paravirq_domain);
+ BUG_ON(nr_irqs != 1);
+
+ irq_data = irq_domain_get_irq_data(paravirq_domain, virq);
+ if (irq_data)
+ irq_domain_reset_irq_data(irq_data);
+ else
+ pr_warn("irq %u is not in paravirq irq_domain\n", virq);
+}
+
+static const struct irq_domain_ops paravirq_domain_ops = {
+ .alloc = paravirq_domain_alloc,
+ .free = paravirq_domain_free,
+};
+
+int paravirq_alloc_irq(void)
+{
+ struct irq_alloc_info info;
+
+ if (!paravirq_domain)
+ return -ENODEV;
+
+ if (!paravirq_chip.irq_mask || !paravirq_chip.irq_unmask)
+ return -EINVAL;
+
+ init_irq_alloc_info(&info, NULL);
+
+ return irq_domain_alloc_irqs(paravirq_domain, 1, NUMA_NO_NODE, &info);
+}
+EXPORT_SYMBOL(paravirq_alloc_irq);
+
+void paravirq_free_irq(unsigned int virq)
+{
+ struct irq_data *irq_data;
+
+ if (!paravirq_domain) {
+ pr_warn("paravirq irq_domain is not initialized\n");
+ return;
+ }
+
+ irq_data = irq_domain_get_irq_data(paravirq_domain, virq);
+ if (irq_data)
+ irq_domain_free_irqs(virq, 1);
+ else
+ pr_warn("irq %u is not in paravirq irq_domain\n", virq);
+}
+EXPORT_SYMBOL(paravirq_free_irq);
+
+int paravirq_init_chip(void (*irq_mask)(struct irq_data *data),
+ void (*irq_unmask)(struct irq_data *data))
+{
+ if (!paravirq_domain)
+ return -ENODEV;
+
+ if (paravirq_chip.irq_mask || paravirq_chip.irq_unmask)
+ return -EEXIST;
+
+ if (!irq_mask || !irq_unmask)
+ return -EINVAL;
+
+ paravirq_chip.irq_mask = irq_mask;
+ paravirq_chip.irq_unmask = irq_unmask;
+
+ return 0;
+}
+EXPORT_SYMBOL(paravirq_init_chip);
+
+void arch_init_paravirq_domain(struct irq_domain *parent)
+{
+ paravirq_domain = irq_domain_add_tree(NULL, ¶virq_domain_ops, NULL);
+ if (!paravirq_domain) {
+ pr_warn("failed to initialize paravirq irq_domain\n");
+ return;
+ }
+
+ paravirq_domain->name = paravirq_chip.name;
+ paravirq_domain->parent = parent;
+ paravirq_domain->flags |= IRQ_DOMAIN_FLAG_AUTO_RECURSIVE;
+}
+
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 6066d94..878b440 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -438,6 +438,7 @@ int __init arch_early_irq_init(void)
arch_init_msi_domain(x86_vector_domain);
arch_init_htirq_domain(x86_vector_domain);
+ arch_init_paravirq_domain(x86_vector_domain);
BUG_ON(!alloc_cpumask_var(&vector_cpumask, GFP_KERNEL));
BUG_ON(!alloc_cpumask_var(&vector_searchmask, GFP_KERNEL));
--
2.5.5
--
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