On 2014/9/17 1:47, Thomas Gleixner wrote:

On Thu, 11 Sep 2014, Jiang Liu wrote:

quoted

Cache destination CPU APIC ID into struct irq_cfg when assigning vector
for interrupt. Upper layer just needs to read the cached APIC ID instead
of calling apic->cpu_mask_to_apicid_and(), it helps to hide APIC driver
details from IOAPIC/HPET/MSI drivers..

Signed-off-by: Jiang Liu <redacted>
---
 arch/x86/include/asm/hw_irq.h |    1 +
 arch/x86/kernel/apic/vector.c |    4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 7624fffc2822..3d51d74d6c01 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h

@@ -116,6 +116,7 @@ struct irq_data;
 struct irq_cfg {
 	cpumask_var_t		domain;
 	cpumask_var_t		old_domain;
+	unsigned int		dest_apicid;
 	u8			vector;
 	u8			move_in_progress : 1;
 #ifdef CONFIG_IRQ_REMAP

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 7562cb15b3bd..287ae4e8d500 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c

@@ -188,6 +188,10 @@ next:
 	}
 	free_cpumask_var(tmp_mask);

Lacks a comment what this call is actually doing.

How about this?
/* cache destination APIC IDs into cfg->dest_apicid */
Regards!
Gerry

quoted

+	if (!err)
+		err = apic->cpu_mask_to_apicid_and(mask, cfg->domain,
+						   &cfg->dest_apicid);
+

Thanks,

	tglx