[PATCH 3/4] x86: Add Numachip IPI optimisations

From: Daniel J Blueman
Date: Sun Sep 20 2015 - 13:17:18 EST


When sending IPIs, first check if the non-local part of the source and
destination APIC IDs match; if so, send via the local APIC for efficiency.

Secondly, since the AMD BIOS-kernel developer guide states IPI delivery
will occur invarient of prior deliver status, avoid polling the delivery
status bit for efficiency.

Signed-off-by: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
Acked-by: Steffen Persvold <sp@xxxxxxxxxxxxx>
---
arch/x86/include/asm/numachip/numachip_csr.h | 1 +
arch/x86/kernel/apic/apic_numachip.c | 36 ++++++++++++++++++++++++----
2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/numachip/numachip_csr.h b/arch/x86/include/asm/numachip/numachip_csr.h
index c7efc25..75379f6 100644
--- a/arch/x86/include/asm/numachip/numachip_csr.h
+++ b/arch/x86/include/asm/numachip/numachip_csr.h
@@ -34,6 +34,7 @@
#define NUMACHIP_LCSR_BASE 0x3ffffe000000ULL
#define NUMACHIP_LCSR_LIM 0x3fffffffffffULL
#define NUMACHIP_LCSR_SIZE (NUMACHIP_LCSR_LIM - NUMACHIP_LCSR_BASE + 1)
+#define NUMACHIP_LAPIC_BITS 8

static inline void *lcsr_address(unsigned long offset)
{
diff --git a/arch/x86/kernel/apic/apic_numachip.c b/arch/x86/kernel/apic/apic_numachip.c
index dfe2b1c..81bc216 100644
--- a/arch/x86/kernel/apic/apic_numachip.c
+++ b/arch/x86/kernel/apic/apic_numachip.c
@@ -95,9 +95,25 @@ static int numachip_wakeup_secondary(int phys_apicid, unsigned long start_rip)

static void numachip_send_IPI_one(int cpu, int vector)
{
- int apicid = per_cpu(x86_cpu_to_apicid, cpu);
+ int local_apicid, apicid = per_cpu(x86_cpu_to_apicid, cpu);
unsigned int dmode;

+ preempt_disable();
+ local_apicid = __this_cpu_read(x86_cpu_to_apicid);
+
+ /* Send via local APIC where non-local part matches */
+ if (!((apicid ^ local_apicid) >> NUMACHIP_LAPIC_BITS)) {
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __default_send_IPI_dest_field(apicid, vector,
+ APIC_DEST_PHYSICAL);
+ local_irq_restore(flags);
+ preempt_enable();
+ return;
+ }
+ preempt_enable();
+
dmode = (vector == NMI_VECTOR) ? APIC_DM_NMI : APIC_DM_FIXED;
numachip_apic_icr_write(apicid, dmode | vector);
}
@@ -217,6 +232,17 @@ static int numachip2_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
return 1;
}

+/* APIC IPIs are queued */
+static void numachip_apic_wait_icr_idle(void)
+{
+}
+
+/* APIC NMI IPIs are queued */
+static u32 numachip_safe_apic_wait_icr_idle(void)
+{
+ return 0;
+}
+
static const struct apic apic_numachip1 __refconst = {
.name = "NumaConnect system",
.probe = numachip1_probe,
@@ -262,8 +288,8 @@ static const struct apic apic_numachip1 __refconst = {
.eoi_write = native_apic_mem_write,
.icr_read = native_apic_icr_read,
.icr_write = native_apic_icr_write,
- .wait_icr_idle = native_apic_wait_icr_idle,
- .safe_wait_icr_idle = native_safe_apic_wait_icr_idle,
+ .wait_icr_idle = numachip_apic_wait_icr_idle,
+ .safe_wait_icr_idle = numachip_safe_apic_wait_icr_idle,
};

apic_driver(apic_numachip1);
@@ -313,8 +339,8 @@ static const struct apic apic_numachip2 __refconst = {
.eoi_write = native_apic_mem_write,
.icr_read = native_apic_icr_read,
.icr_write = native_apic_icr_write,
- .wait_icr_idle = native_apic_wait_icr_idle,
- .safe_wait_icr_idle = native_safe_apic_wait_icr_idle,
+ .wait_icr_idle = numachip_apic_wait_icr_idle,
+ .safe_wait_icr_idle = numachip_safe_apic_wait_icr_idle,
};

apic_driver(apic_numachip2);
--
2.5.0

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