[RFC -tip] apic NOOP driver

[Cyrill Gorcunov]

Ingo,

here is what implemented at moment. Did you mean something like that?
Note that it's quite early RFC not for any kind of inclusion.

Actually compiled driver eats about ~1.3K of memory so perhaps
the better option would be to just implement noop read/write and IPI calls
leaving all other calls NULLified -- it'll cause NULL deref but the
fact is that the former operations are called that deep in
apic/io-apic code where they shouldn't be touched at all and
even issue warning (as noop does) should be substituted with panic
I think (though I tried to put return values for noop operations more
or less sane here).

What else... NOOP_FUNC macros looks fishy but can't imagine at moment
anything more elegant instead of open coded functions.

Anyway, I would appreciate any comments (negative comments too of course :)

	-- Cyrill
---
x86,apic: introduce NOOP apic driver

Introduce NOOP APIC driver. We use it in case if apic was disabled
due to hardware of software/firmware problems (including user requested
to disable it case).

The driver is attempting to catch any inappropriate apic operation
call with warning issue.

Also it is possible to use some apic operation like IPI calls, read/write
without checking for apic presence which should make callers code easier.

Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
---
 arch/x86/include/asm/apic.h      |    2 
 arch/x86/kernel/apic/Makefile    |    2 
 arch/x86/kernel/apic/apic.c      |   22 ----
 arch/x86/kernel/apic/apic_noop.c |  194 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 200 insertions(+), 20 deletions(-)

Index: linux-2.6.git/arch/x86/include/asm/apic.h
=====================================================================
--- linux-2.6.git.orig/arch/x86/include/asm/apic.h
+++ linux-2.6.git/arch/x86/include/asm/apic.h
@@ -488,6 +488,8 @@ static inline unsigned int read_apic_id(
 
 extern void default_setup_apic_routing(void);
 
+extern struct apic apic_noop;
+
 #ifdef CONFIG_X86_32
 
 extern struct apic apic_default;
Index: linux-2.6.git/arch/x86/kernel/apic/Makefile
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/Makefile
+++ linux-2.6.git/arch/x86/kernel/apic/Makefile
@@ -2,7 +2,7 @@
 # Makefile for local APIC drivers and for the IO-APIC code
 #
 
-obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o probe_$(BITS).o ipi.o nmi.o
+obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o apic_noop.o probe_$(BITS).o ipi.o nmi.o
 obj-$(CONFIG_X86_IO_APIC)	+= io_apic.o
 obj-$(CONFIG_SMP)		+= ipi.o
 
Index: linux-2.6.git/arch/x86/kernel/apic/apic.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6.git/arch/x86/kernel/apic/apic.c
@@ -241,28 +241,12 @@ static int modern_apic(void)
 }
 
 /*
- * bare function to substitute write operation
- * and it's _that_ fast :)
- */
-static void native_apic_write_dummy(u32 reg, u32 v)
-{
-	WARN_ON_ONCE((cpu_has_apic || !disable_apic));
-}
-
-static u32 native_apic_read_dummy(u32 reg)
-{
-	WARN_ON_ONCE((cpu_has_apic && !disable_apic));
-	return 0;
-}
-
-/*
- * right after this call apic->write/read doesn't do anything
- * note that there is no restore operation it works one way
+ * right after this call apic become NOOP driven
+ * so apic->write/read doesn't do anything
  */
 void apic_disable(void)
 {
-	apic->read = native_apic_read_dummy;
-	apic->write = native_apic_write_dummy;
+	apic = &apic_noop;
 }
 
 void native_apic_wait_icr_idle(void)
Index: linux-2.6.git/arch/x86/kernel/apic/apic_noop.c
=====================================================================
--- /dev/null
+++ linux-2.6.git/arch/x86/kernel/apic/apic_noop.c
@@ -0,0 +1,194 @@
+/*
+ * NOOP APIC driver.
+ *
+ * Does almost nothing and should be substituted by a real apic driver via
+ * probe routine. Though in case if apic is disabled (for some reason) we try
+ * to not uglify the caller's code and allow to call (some) apic routines
+ * like self-ipi, etc... and issue a warning if an operation is not allowed
+ *
+ */
+
+#include <linux/threads.h>
+#include <linux/cpumask.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <asm/fixmap.h>
+#include <asm/mpspec.h>
+#include <asm/apicdef.h>
+#include <asm/apic.h>
+#include <asm/setup.h>
+
+#include <linux/smp.h>
+#include <asm/ipi.h>
+
+#include <linux/interrupt.h>
+#include <asm/acpi.h>
+#include <asm/e820.h>
+
+/*
+ * some operations should never be reached with
+ * noop apic if it's not turned off, this mostly
+ * means the caller forgot to disable apic (or
+ * check the apic presence) before doing a call
+ */
+static void warn_apic_enabled(void)
+{
+	WARN_ONCE((cpu_has_apic || !disable_apic),
+		"APIC: Called for NOOP operation with apic enabled\n");
+}
+
+/*
+ * To check operations but do not bloat source code
+ */
+#define NOOP_FUNC(func)			func { warn_apic_enabled(); }
+#define NOOP_FUNC_RET(func, ret)	func { warn_apic_enabled(); return ret; }
+
+NOOP_FUNC(static void noop_init_apic_ldr(void));
+NOOP_FUNC(static void noop_send_IPI_mask(const struct cpumask *cpumask, int vector));
+NOOP_FUNC(static void noop_send_IPI_mask_allbutself(const struct cpumask *cpumask, int vector));
+NOOP_FUNC(static void noop_send_IPI_allbutself(int vector));
+NOOP_FUNC(static void noop_send_IPI_all(int vector));
+NOOP_FUNC(static void noop_send_IPI_self(int vector));
+NOOP_FUNC_RET(static int noop_wakeup_secondary_cpu(int apicid, unsigned long start_eip), -1);
+NOOP_FUNC(static void noop_apic_write(u32 reg, u32 v));
+NOOP_FUNC(void noop_apic_wait_icr_idle(void));
+NOOP_FUNC_RET(static u32 noop_safe_apic_wait_icr_idle(void), 0);
+NOOP_FUNC_RET(static u64 noop_apic_icr_read(void), 0);
+NOOP_FUNC(static void noop_apic_icr_write(u32 low, u32 id));
+NOOP_FUNC_RET(static physid_mask_t noop_ioapic_phys_id_map(physid_mask_t phys_map), phys_map);
+NOOP_FUNC_RET(static int noop_cpu_to_logical_apicid(int cpu), 1);
+NOOP_FUNC_RET(static int noop_default_phys_pkg_id(int cpuid_apic, int index_msb), 0);
+NOOP_FUNC_RET(static unsigned int noop_get_apic_id(unsigned long x), 0);
+
+static int noop_probe(void)
+{
+	/* should not ever be enabled this way */
+	return 0;
+}
+
+static int noop_apic_id_registered(void)
+{
+	warn_apic_enabled();
+
+	return physid_isset(read_apic_id(), phys_cpu_present_map);
+}
+
+static const struct cpumask *noop_target_cpus(void)
+{
+	warn_apic_enabled();
+
+	/* only BSP here */
+	return cpumask_of(0);
+}
+
+static unsigned long noop_check_apicid_used(physid_mask_t bitmap, int apicid)
+{
+	warn_apic_enabled();
+	return physid_isset(apicid, bitmap);
+}
+
+static unsigned long noop_check_apicid_present(int bit)
+{
+	warn_apic_enabled();
+	return physid_isset(bit, phys_cpu_present_map);
+}
+
+static void noop_vector_allocation_domain(int cpu, struct cpumask *retmask)
+{
+	warn_apic_enabled();
+	if (cpu != 0)
+		pr_warning("APIC: Vector allocated for non-BSP cpu\n");
+	cpumask_clear(retmask);
+	cpumask_set_cpu(cpu, retmask);
+}
+
+int noop_apicid_to_node(int logical_apicid)
+{
+	warn_apic_enabled();
+
+	/* we're always on node 0 */
+	return 0;
+}
+
+static u32 noop_apic_read(u32 reg)
+{
+	/*
+	 * noop-read is always safe until we have
+	 * non-disabled unit
+	 */
+	WARN_ON_ONCE((cpu_has_apic && !disable_apic));
+	return 0;
+}
+
+struct apic apic_noop = {
+	.name				= "noop",
+	.probe				= noop_probe,
+	.acpi_madt_oem_check		= NULL,
+
+	.apic_id_registered		= noop_apic_id_registered,
+
+	.irq_delivery_mode		= dest_LowestPrio,
+	/* logical delivery broadcast to all CPUs: */
+	.irq_dest_mode			= 1,
+
+	.target_cpus			= noop_target_cpus,
+	.disable_esr			= 0,
+	.dest_logical			= APIC_DEST_LOGICAL,
+	.check_apicid_used		= noop_check_apicid_used,
+	.check_apicid_present		= noop_check_apicid_present,
+
+	.vector_allocation_domain	= noop_vector_allocation_domain,
+	.init_apic_ldr			= noop_init_apic_ldr,
+
+	.ioapic_phys_id_map		= noop_ioapic_phys_id_map,
+	.setup_apic_routing		= NULL,
+	.multi_timer_check		= NULL,
+	.apicid_to_node			= noop_apicid_to_node,
+
+	.cpu_to_logical_apicid		= noop_cpu_to_logical_apicid,
+	.cpu_present_to_apicid		= default_cpu_present_to_apicid,
+	.apicid_to_cpu_present		= default_apicid_to_cpu_present,
+
+	.setup_portio_remap		= NULL,
+	.check_phys_apicid_present	= default_check_phys_apicid_present,
+	.enable_apic_mode		= NULL,
+
+	.phys_pkg_id			= noop_default_phys_pkg_id,
+
+	.mps_oem_check			= NULL,
+
+	.get_apic_id			= noop_get_apic_id,
+	.set_apic_id			= NULL,
+	.apic_id_mask			= 0x0F << 24,
+
+	.cpu_mask_to_apicid		= default_cpu_mask_to_apicid,
+	.cpu_mask_to_apicid_and		= default_cpu_mask_to_apicid_and,
+
+	.send_IPI_mask			= noop_send_IPI_mask,
+	.send_IPI_mask_allbutself	= noop_send_IPI_mask_allbutself,
+	.send_IPI_allbutself		= noop_send_IPI_allbutself,
+	.send_IPI_all			= noop_send_IPI_all,
+	.send_IPI_self			= noop_send_IPI_self,
+
+	.wakeup_secondary_cpu		= noop_wakeup_secondary_cpu,
+
+	/* should be safe */
+	.trampoline_phys_low		= DEFAULT_TRAMPOLINE_PHYS_LOW,
+	.trampoline_phys_high		= DEFAULT_TRAMPOLINE_PHYS_HIGH,
+
+	.wait_for_init_deassert		= NULL,
+
+	.smp_callin_clear_local_apic	= NULL,
+	.inquire_remote_apic		= NULL,
+
+	.read				= noop_apic_read,
+	.write				= noop_apic_write,
+	.icr_read			= noop_apic_icr_read,
+	.icr_write			= noop_apic_icr_write,
+	.wait_icr_idle			= noop_apic_wait_icr_idle,
+	.safe_wait_icr_idle		= noop_safe_apic_wait_icr_idle,
+};
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/