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SubjectRe: [RFC -tip] x86: do_IRQ - send APIC EOI for x86-32 on irq without handler v3
[Ingo Molnar - Fri, Apr 10, 2009 at 04:00:23PM +0200]
|
| * Cyrill Gorcunov <gorcunov@gmail.com> wrote:
|
| > [Ingo Molnar - Fri, Apr 10, 2009 at 02:27:50PM +0200]
| > |
| > | * Cyrill Gorcunov <gorcunov@openvz.org> wrote:
| > |
| > | > Ingo, I've checked the sources and as far as I see
| > | > we could NOP'ify apic->write indeed but I have
| > | > an internal feeling that this will bring us more problem
| > | > in future (for example it could be the following scenario:
| > | > some screwed APIC would require cleaning of LVT's or
| > | > IRR after resume regardless if it was initialized
| > | > or not at all). Mostly I mean that the idea of making
| > | > apic->write NOP'ified is quite elegant indeed but
| > | > cut off the subset of apic operations (we need
| > | > apic->read anyway) somehow bothering me from inside :)
| > |
| > | it's as if assigned a special type of 'dummy apic' struct apic. It
| > | wont cause problems down the line: we use the new APIC driver
| > | infrastructure to abstract out quirks.
| >
| > Well, it's not that new actually :-)
|
| Yeah, i mean the new unified/modernized code in 2.6.30-to-be.
|
| > |
| > | one small detail:
| > |
| > | > +/* Ack APIC irq if it's enabled only */
| > | > +static inline void ack_APIC_irq_safe(void)
| > | > +{
| > | > +#ifdef CONFIG_X86_LOCAL_APIC
| > | > + if (cpu_has_apic)
| > | > + ack_APIC_irq();
| > | > +#endif
| > |
| > | we dont need the cpu_has_apic check there, do we? In the
| > | !cpu_has_apic the ->write method should be a dummy.
| >
| > Yes. In case you're talking about it'll not be needed
| > (we will find earlier whether cpu_has_apic or not).
|
| yeah.
|
| Ingo
|

Ingo,

I think you meant something like the patch below. It's
not finished yet -- I need to find out right place for
calling freshly introduced apic_disable_write_op.
Will continue tomorrow.

But even having it not completed yet I would like to
get some feedbackabout code structure in general.

Cyrill
---
arch/x86/include/asm/apic.h | 10 ++++++++++
arch/x86/kernel/apic/apic.c | 6 ++++++
arch/x86/kernel/irq.c | 10 ++--------
3 files changed, 18 insertions(+), 8 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
@@ -106,6 +106,7 @@ extern void native_apic_wait_icr_idle(vo
extern u32 native_safe_apic_wait_icr_idle(void);
extern void native_apic_icr_write(u32 low, u32 id);
extern u64 native_apic_icr_read(void);
+extern void native_apic_write_dummy(u32 reg, u32 v);

#define EIM_8BIT_APIC_ID 0
#define EIM_32BIT_APIC_ID 1
@@ -372,6 +373,15 @@ static inline void apic_write(u32 reg, u
apic->write(reg, val);
}

+/*
+ * right after this call apic->write doesn't do anything
+ * note that there is no restore operation it works one way
+ */
+static inline void apic_disable_write_op(void)
+{
+ apic->write = native_apic_write_dummy;
+}
+
static inline u64 apic_icr_read(void)
{
return apic->icr_read();
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
@@ -210,6 +210,12 @@ static int modern_apic(void)
return lapic_get_version() >= 0x14;
}

+/*
+ * bare function to substitute write operation
+ * and it's _that_ fast :)
+ */
+void native_apic_write_dummy(u32 reg, u32 v) { }
+
void native_apic_wait_icr_idle(void)
{
while (apic_read(APIC_ICR) & APIC_ICR_BUSY)
Index: linux-2.6.git/arch/x86/kernel/irq.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/irq.c
+++ linux-2.6.git/arch/x86/kernel/irq.c
@@ -27,7 +27,6 @@ void ack_bad_irq(unsigned int irq)
if (printk_ratelimit())
pr_err("unexpected IRQ trap at vector %02x\n", irq);

-#ifdef CONFIG_X86_LOCAL_APIC
/*
* Currently unexpected vectors happen only on SMP and APIC.
* We _must_ ack these because every local APIC has only N
@@ -37,9 +36,7 @@ void ack_bad_irq(unsigned int irq)
* completely.
* But only ack when the APIC is enabled -AK
*/
- if (cpu_has_apic)
- ack_APIC_irq();
-#endif
+ ack_APIC_irq();
}

#define irq_stats(x) (&per_cpu(irq_stat, x))
@@ -224,10 +221,7 @@ unsigned int __irq_entry do_IRQ(struct p
irq = __get_cpu_var(vector_irq)[vector];

if (!handle_irq(irq, regs)) {
-#ifdef CONFIG_X86_64
- if (!disable_apic)
- ack_APIC_irq();
-#endif
+ ack_APIC_irq();

if (printk_ratelimit())
pr_emerg("%s: %d.%d No irq handler for vector (irq %d)\n",

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