powerpc: Rework lazy-interrupt handling
The current implementation of lazy interrupts handling has some
issues that this tries to address.
We don't do the various workarounds we need to do when re-enabling
interrupts in some cases such as when returning from an interrupt
and thus we may still lose or get delayed decrementer or doorbell
interrupts.
The current scheme also makes it much harder to handle the external
"edge" interrupts provided by some BookE processors when using the
EPR facility (External Proxy) and the Freescale Hypervisor.
Additionally, we tend to keep interrupts hard disabled in a number
of cases, such as decrementer interrupts, external interrupts, or
when a masked decrementer interrupt is pending. This is sub-optimal.
This is an attempt at fixing it all in one go by reworking the way
we do the lazy interrupt disabling from the ground up.
The base idea is to replace the "hard_enabled" field with a
"irq_happened" field in which we store a bit mask of what interrupt
occurred while soft-disabled.
When re-enabling, either via arch_local_irq_restore() or when returning
from an interrupt, we can now decide what to do by testing bits in that
field.
We then implement replaying of the missed interrupts either by
re-using the existing exception frame (in exception exit case) or via
the creation of a new one from an assembly trampoline (in the
arch_local_irq_enable case).
This removes the need to play with the decrementer to try to create
fake interrupts, among others.
In addition, this adds a few refinements:
- We no longer hard disable decrementer interrupts that occur
while soft-disabled. We now simply bump the decrementer back to max
(on BookS) or leave it stopped (on BookE) and continue with hard interrupts
enabled, which means that we'll potentially get better sample quality from
performance monitor interrupts.
- Timer, decrementer and doorbell interrupts now hard-enable
shortly after removing the source of the interrupt, which means
they no longer run entirely hard disabled. Again, this will improve
perf sample quality.
- On Book3E 64-bit, we now make the performance monitor interrupt
act as an NMI like Book3S (the necessary C code for that to work
appear to already be present in the FSL perf code, notably calling
nmi_enter instead of irq_enter). (This also fixes a bug where BookE
perfmon interrupts could clobber r14 ... oops)
- We could make "masked" decrementer interrupts act as NMIs when doing
timer-based perf sampling to improve the sample quality.
Signed-off-by-yet: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
v2:
- Add hard-enable to decrementer, timer and doorbells
- Fix CR clobber in masked irq handling on BookE
- Make embedded perf interrupt act as an NMI
- Add a PACA_HAPPENED_EE_EDGE for use by FSL if they want
to retrigger an interrupt without preventing hard-enable
v3:
- Fix or vs. ori bug on Book3E
- Fix enabling of interrupts for some exceptions on Book3E
v4:
- Fix resend of doorbells on return from interrupt on Book3E
v5:
- Rebased on top of my latest series, which involves some significant
rework of some aspects of the patch.
v6:
- 32-bit compile fix
- more compile fixes with various .config combos
- factor out the asm code to soft-disable interrupts
- remove the C wrapper around preempt_schedule_irq
v7:
- Fix a bug with hard irq state tracking on native power7
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 02448ea..2d0868a 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -12,6 +12,7 @@
*
*/
+#include <asm/hw_irq.h>
#include <asm/exception-64s.h>
#include <asm/ptrace.h>
@@ -356,34 +357,60 @@
KVM_HANDLER_PR(PACA_EXGEN, EXC_STD, 0xf40)
/*
- * An interrupt came in while soft-disabled; clear EE in SRR1,
- * clear paca->hard_enabled and return.
+ * An interrupt came in while soft-disabled. We set paca->irq_happened,
+ * then, if it was a decrementer interrupt, we bump the dec to max and
+ * and return, else we hard disable and return. This is called with
+ * r10 containing the value to OR to the paca field.
*/
-masked_interrupt:
- stb r10,PACAHARDIRQEN(r13)
- mtcrf 0x80,r9
- ld r9,PACA_EXGEN+EX_R9(r13)
- mfspr r10,SPRN_SRR1
- rldicl r10,r10,48,1 /* clear MSR_EE */
- rotldi r10,r10,16
- mtspr SPRN_SRR1,r10
- ld r10,PACA_EXGEN+EX_R10(r13)
- GET_SCRATCH0(r13)
- rfid
+#define MASKED_INTERRUPT(_H) \
+masked_##_H##interrupt: \
+ std r11,PACA_EXGEN+EX_R11(r13); \
+ lbz r11,PACAIRQHAPPENED(r13); \
+ or r11,r11,r10; \
+ stb r11,PACAIRQHAPPENED(r13); \
+ andi. r10,r10,PACA_IRQ_DEC; \
+ beq 1f; \
+ lis r10,0x7fff; \
+ ori r10,r10,0xffff; \
+ mtspr SPRN_DEC,r10; \
+ b 2f; \
+1: mfspr r10,SPRN_##_H##SRR1; \
+ rldicl r10,r10,48,1; /* clear MSR_EE */ \
+ rotldi r10,r10,16; \
+ mtspr SPRN_##_H##SRR1,r10; \
+2: mtcrf 0x80,r9; \
+ ld r9,PACA_EXGEN+EX_R9(r13); \
+ ld r10,PACA_EXGEN+EX_R10(r13); \
+ ld r11,PACA_EXGEN+EX_R11(r13); \
+ GET_SCRATCH0(r13); \
+ ##_H##rfid; \
b .
+
+ MASKED_INTERRUPT()
+ MASKED_INTERRUPT(H)
-masked_Hinterrupt:
- stb r10,PACAHARDIRQEN(r13)
- mtcrf 0x80,r9
- ld r9,PACA_EXGEN+EX_R9(r13)
- mfspr r10,SPRN_HSRR1
- rldicl r10,r10,48,1 /* clear MSR_EE */
- rotldi r10,r10,16
- mtspr SPRN_HSRR1,r10
- ld r10,PACA_EXGEN+EX_R10(r13)
- GET_SCRATCH0(r13)
- hrfid
- b .
+/*
+ * Called from arch_local_irq_enable when an interrupt needs
+ * to be resent. r3 contains 0x500 or 0x900 to indicate which
+ * kind of interrupt. MSR:EE is already off. We generate a
+ * stackframe like if a real interrupt had happened.
+ *
+ * Note: While MSR:EE is off, we need to make sure that _MSR
+ * in the generated frame has EE set to 1 or the exception
+ * handler will not properly re-enable them.
+ */
+_GLOBAL(__replay_interrupt)
+ /* We are going to jump to the exception common code which
+ * will retrieve various register values from the PACA which
+ * we don't give a damn about, so we don't bother storing them.
+ */
+ mfmsr r12
+ mflr r11
+ mfcr r9
+ ori r12,r12,MSR_EE
+ andi. r3,r3,0x0800
+ bne decrementer_common
+ b hardware_interrupt_common
#ifdef CONFIG_PPC_PSERIES
/*
@@ -793,7 +820,8 @@
EXCEPTION_PROLOG_COMMON(0xf40, PACA_EXGEN)
#ifdef CONFIG_VSX
BEGIN_FTR_SECTION
- bne .load_up_vsx
+ beq 1f
+ b .load_up_vsx
1:
END_FTR_SECTION_IFSET(CPU_FTR_VSX)
#endif
@@ -808,65 +836,6 @@
__end_handlers:
/*
- * Return from an exception with minimal checks.
- * The caller is assumed to have done EXCEPTION_PROLOG_COMMON.
- * If interrupts have been enabled, or anything has been
- * done that might have changed the scheduling status of
- * any task or sent any task a signal, you should use
- * ret_from_except or ret_from_except_lite instead of this.
- */
-fast_exc_return_irq: /* restores irq state too */
- ld r3,SOFTE(r1)
- TRACE_AND_RESTORE_IRQ(r3);
- ld r12,_MSR(r1)
- rldicl r4,r12,49,63 /* get MSR_EE to LSB */
- stb r4,PACAHARDIRQEN(r13) /* restore paca->hard_enabled */
- b 1f
-
- .globl fast_exception_return
-fast_exception_return:
- ld r12,_MSR(r1)
-1: ld r11,_NIP(r1)
- andi. r3,r12,MSR_RI /* check if RI is set */
- beq- unrecov_fer
-
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING
- andi. r3,r12,MSR_PR
- beq 2f
- ACCOUNT_CPU_USER_EXIT(r3, r4)
-2:
-#endif
-
- ld r3,_CCR(r1)
- ld r4,_LINK(r1)
- ld r5,_CTR(r1)
- ld r6,_XER(r1)
- mtcr r3
- mtlr r4
- mtctr r5
- mtxer r6
- REST_GPR(0, r1)
- REST_8GPRS(2, r1)
-
- ld r10,PACAKMSR(r13)
- clrrdi r10,r10,2 /* clear RI */
- mtmsrd r10,1
-
- mtspr SPRN_SRR1,r12
- mtspr SPRN_SRR0,r11
- REST_4GPRS(10, r1)
- ld r1,GPR1(r1)
- rfid
- b . /* prevent speculative execution */
-
-unrecov_fer:
- bl .save_nvgprs
-1: addi r3,r1,STACK_FRAME_OVERHEAD
- bl .unrecoverable_exception
- b 1b
-
-
-/*
* Hash table stuff
*/
.align 7
@@ -905,19 +874,16 @@
* r4 contains the required access permissions
* r5 contains the trap number
*
- * at return r3 = 0 for success
+ * at return r3 = 0 for success, 1 for page fault, negative for error
*/
bl .hash_page /* build HPTE if possible */
cmpdi r3,0 /* see if hash_page succeeded */
- /*
- * Here we have interrupts hard-disabled, so it is sufficient
- * to restore paca->{soft,hard}_enable and get out.
- */
+ /* Success */
beq fast_exc_return_irq /* Return from exception on success */
- /* For a hash failure, we don't bother re-enabling interrupts */
- ble- 13f
+ /* Error */
+ blt- 13f
/* Here we have a page fault that hash_page can't handle. */
handle_page_fault: