genirq: Implement bitmap matrix allocator

Implement the infrastructure for a simple bitmap based allocator, which
will replace the x86 vector allocator. It's in the core code as other
architectures might be able to reuse/extend it. For now it only implements
allocations for single CPUs, but it's simple to add multi CPU allocation
support if required.

The concept is rather simple:

 Global information:
 	system_vector bitmap
	global accounting

 PerCPU information:
 	allocation bitmap
	managed allocation bitmap
	local accounting

The system vector bitmap is used to exclude vectors system wide from the
allocation space.

The allocation bitmap is used to keep track of per cpu used vectors.

The managed allocation bitmap is used to reserve vectors for managed
interrupts.

When a regular (non managed) interrupt allocation happens then the
following rule applies:

      tmpmap = system_map | alloc_map | managed_map
      find_zero_bit(tmpmap)

Oring the bitmaps together gives the real available space. The same rule
applies for reserving a managed interrupt vector. But contrary to the
regular interrupts the reservation only marks the bit in the managed map
and therefor excludes it from the regular allocations. The managed map is
only cleaned out when the a managed interrupt is completely released and it
stays alive accross CPU offline/online operations.

For managed interrupt allocations the rule is:

      tmpmap = managed_map & ~alloc_map
      find_first_bit(tmpmap)

This returns the first bit which is in the managed map, but not yet
allocated in the allocation map. The allocation marks it in the allocation
map and hands it back to the caller for use.

The rest of the code are helper functions to handle the various
requirements and the accounting which are necessary to replace the x86
vector allocation code. The result is a single patch as the evolution of
this infrastructure cannot be represented in bits and pieces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Yu Chen <yu.c.chen@intel.com>
Acked-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rui Zhang <rui.zhang@intel.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Len Brown <lenb@kernel.org>
Link: https://lkml.kernel.org/r/20170913213153.185437174@linutronix.de

include/linux/irq.h

@@ -1113,6 +1113,28 @@ static inline u32 irq_reg_readl(struct irq_chip_generic *gc,
 		return readl(gc->reg_base + reg_offset);
 }
 
+struct irq_matrix;
+struct irq_matrix *irq_alloc_matrix(unsigned int matrix_bits,
+				    unsigned int alloc_start,
+				    unsigned int alloc_end);
+void irq_matrix_online(struct irq_matrix *m);
+void irq_matrix_offline(struct irq_matrix *m);
+void irq_matrix_assign_system(struct irq_matrix *m, unsigned int bit, bool replace);
+int irq_matrix_reserve_managed(struct irq_matrix *m, const struct cpumask *msk);
+void irq_matrix_remove_managed(struct irq_matrix *m, const struct cpumask *msk);
+int irq_matrix_alloc_managed(struct irq_matrix *m, unsigned int cpu);
+void irq_matrix_reserve(struct irq_matrix *m);
+void irq_matrix_remove_reserved(struct irq_matrix *m);
+int irq_matrix_alloc(struct irq_matrix *m, const struct cpumask *msk,
+		     bool reserved, unsigned int *mapped_cpu);
+void irq_matrix_free(struct irq_matrix *m, unsigned int cpu,
+		     unsigned int bit, bool managed);
+void irq_matrix_assign(struct irq_matrix *m, unsigned int bit);
+unsigned int irq_matrix_available(struct irq_matrix *m, bool cpudown);
+unsigned int irq_matrix_allocated(struct irq_matrix *m);
+unsigned int irq_matrix_reserved(struct irq_matrix *m);
+void irq_matrix_debug_show(struct seq_file *sf, struct irq_matrix *m, int ind);
+
 /* Contrary to Linux irqs, for hardware irqs the irq number 0 is valid */
 #define INVALID_HWIRQ	(~0UL)
 irq_hw_number_t ipi_get_hwirq(unsigned int irq, unsigned int cpu);

kernel/irq/Kconfig

@@ -97,6 +97,9 @@ config HANDLE_DOMAIN_IRQ
 config IRQ_TIMINGS
 	bool
 
+config GENERIC_IRQ_MATRIX_ALLOCATOR
+	bool
+
 config IRQ_DOMAIN_DEBUG
 	bool "Expose hardware/virtual IRQ mapping via debugfs"
 	depends on IRQ_DOMAIN && DEBUG_FS

kernel/irq/Makefile

@@ -13,3 +13,4 @@ obj-$(CONFIG_GENERIC_MSI_IRQ) += msi.o
 obj-$(CONFIG_GENERIC_IRQ_IPI) += ipi.o
 obj-$(CONFIG_SMP) += affinity.o
 obj-$(CONFIG_GENERIC_IRQ_DEBUGFS) += debugfs.o
+obj-$(CONFIG_GENERIC_IRQ_MATRIX_ALLOCATOR) += matrix.o