KVM: PPC: Book3S HV: Consolidate code that checks reason for wake from nap

Currently in book3s_hv_rmhandlers.S we have three places where we
have woken up from nap mode and we check the reason field in SRR1
to see what event woke us up.  This consolidates them into a new
function, kvmppc_check_wake_reason.  It looks at the wake reason
field in SRR1, and if it indicates that an external interrupt caused
the wakeup, calls kvmppc_read_intr to check what sort of interrupt
it was.

This also consolidates the two places where we synthesize an external
interrupt (0x500 vector) for the guest.  Now, if the guest exit code
finds that there was an external interrupt which has been handled
(i.e. it was an IPI indicating that there is now an interrupt pending
for the guest), it jumps to deliver_guest_interrupt, which is in the
last part of the guest entry code, where we synthesize guest external
and decrementer interrupts.  That code has been streamlined a little
and now clears LPCR[MER] when appropriate as well as setting it.

The extra clearing of any pending IPI on a secondary, offline CPU
thread before going back to nap mode has been removed.  It is no longer
necessary now that we have code to read and acknowledge IPIs in the
guest exit path.

This fixes a minor bug in the H_CEDE real-mode handling - previously,
if we found that other threads were already exiting the guest when we
were about to go to nap mode, we would branch to the cede wakeup path
and end up looking in SRR1 for a wakeup reason.  Now we branch to a
point after we have checked the wakeup reason.

This also fixes a minor bug in kvmppc_read_intr - previously it could
return 0xff rather than 1, in the case where we find that a host IPI
is pending after we have cleared the IPI.  Now it returns 1.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -193,8 +193,10 @@ kvm_novcpu_wakeup:
 	stb	r0, HSTATE_NAPPING(r13)
 	stb	r0, HSTATE_HWTHREAD_REQ(r13)
 
+	/* check the wake reason */
+	bl	kvmppc_check_wake_reason
+	
 	/* see if any other thread is already exiting */
-	li	r12, 0
 	lwz	r0, VCORE_ENTRY_EXIT(r5)
 	cmpwi	r0, 0x100
 	bge	kvm_novcpu_exit
@@ -204,23 +206,14 @@ kvm_novcpu_wakeup:
 	li	r0, 1
 	sld	r0, r0, r7
 	addi	r6, r5, VCORE_NAPPING_THREADS
-4:	lwarx	r3, 0, r6
-	andc	r3, r3, r0
-	stwcx.	r3, 0, r6
+4:	lwarx	r7, 0, r6
+	andc	r7, r7, r0
+	stwcx.	r7, 0, r6
 	bne	4b
 
-	/* Check the wake reason in SRR1 to see why we got here */
-	mfspr	r3, SPRN_SRR1
-	rlwinm	r3, r3, 44-31, 0x7	/* extract wake reason field */
-	cmpwi	r3, 4			/* was it an external interrupt? */
-	bne	kvm_novcpu_exit		/* if not, exit the guest */
-
-	/* extern interrupt - read and handle it */
-	li	r12, BOOK3S_INTERRUPT_EXTERNAL
-	bl	kvmppc_read_intr
+	/* See if the wake reason means we need to exit */
 	cmpdi	r3, 0
 	bge	kvm_novcpu_exit
-	li	r12, 0
 
 	/* Got an IPI but other vcpus aren't yet exiting, must be a latecomer */
 	ld	r4, HSTATE_KVM_VCPU(r13)
@@ -264,40 +257,16 @@ kvm_start_guest:
 	 */
 
 	/* Check the wake reason in SRR1 to see why we got here */
-	mfspr	r3,SPRN_SRR1
-	rlwinm	r3,r3,44-31,0x7		/* extract wake reason field */
-	cmpwi	r3,4			/* was it an external interrupt? */
-	bne	27f			/* if not */
-	ld	r5,HSTATE_XICS_PHYS(r13)
-	li	r7,XICS_XIRR		/* if it was an external interrupt, */
-	lwzcix	r8,r5,r7		/* get and ack the interrupt */
-	sync
-	clrldi.	r9,r8,40		/* get interrupt source ID. */
-	beq	28f			/* none there? */
-	cmpwi	r9,XICS_IPI		/* was it an IPI? */
-	bne	29f
-	li	r0,0xff
-	li	r6,XICS_MFRR
-	stbcix	r0,r5,r6		/* clear IPI */
-	stwcix	r8,r5,r7		/* EOI the interrupt */
-	sync				/* order loading of vcpu after that */
+	bl	kvmppc_check_wake_reason
+	cmpdi	r3, 0
+	bge	kvm_no_guest
 
 	/* get vcpu pointer, NULL if we have no vcpu to run */
 	ld	r4,HSTATE_KVM_VCPU(r13)
 	cmpdi	r4,0
 	/* if we have no vcpu to run, go back to sleep */
 	beq	kvm_no_guest
-	b	30f
 
-27:	/* XXX should handle hypervisor maintenance interrupts etc. here */
-	b	kvm_no_guest
-28:	/* SRR1 said external but ICP said nope?? */
-	b	kvm_no_guest
-29:	/* External non-IPI interrupt to offline secondary thread? help?? */
-	stw	r8,HSTATE_SAVED_XIRR(r13)
-	b	kvm_no_guest
-
-30:
 	/* Set HSTATE_DSCR(r13) to something sensible */
 	LOAD_REG_ADDR(r6, dscr_default)
 	ld	r6, 0(r6)
@@ -310,18 +279,6 @@ kvm_start_guest:
 	li	r0, 0
 	std	r0, HSTATE_KVM_VCPU(r13)
 	lwsync
-	/* Clear any pending IPI - we're an offline thread */
-	ld	r5, HSTATE_XICS_PHYS(r13)
-	li	r7, XICS_XIRR
-	lwzcix	r3, r5, r7		/* ack any pending interrupt */
-	rlwinm.	r0, r3, 0, 0xffffff	/* any pending? */
-	beq	37f
-	sync
-	li	r0, 0xff
-	li	r6, XICS_MFRR
-	stbcix	r0, r5, r6		/* clear the IPI */
-	stwcix	r3, r5, r7		/* EOI it */
-37:	sync
 
 	/* increment the nap count and then go to nap mode */
 	ld	r4, HSTATE_KVM_VCORE(r13)
@@ -818,47 +775,46 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
 	mtctr	r6
 	mtxer	r7
 
+kvmppc_cede_reentry:		/* r4 = vcpu, r13 = paca */
 	ld	r10, VCPU_PC(r4)
 	ld	r11, VCPU_MSR(r4)
-kvmppc_cede_reentry:		/* r4 = vcpu, r13 = paca */
 	ld	r6, VCPU_SRR0(r4)
 	ld	r7, VCPU_SRR1(r4)
+	mtspr	SPRN_SRR0, r6
+	mtspr	SPRN_SRR1, r7
 
+deliver_guest_interrupt:
 	/* r11 = vcpu->arch.msr & ~MSR_HV */
 	rldicl	r11, r11, 63 - MSR_HV_LG, 1
 	rotldi	r11, r11, 1 + MSR_HV_LG
 	ori	r11, r11, MSR_ME
 
 	/* Check if we can deliver an external or decrementer interrupt now */
-	ld	r0,VCPU_PENDING_EXC(r4)
-	lis	r8,(1 << BOOK3S_IRQPRIO_EXTERNAL_LEVEL)@h
-	and	r0,r0,r8
-	cmpdi	cr1,r0,0
-	andi.	r0,r11,MSR_EE
-	beq	cr1,11f
+	ld	r0, VCPU_PENDING_EXC(r4)
+	rldicl	r0, r0, 64 - BOOK3S_IRQPRIO_EXTERNAL_LEVEL, 63
+	cmpdi	cr1, r0, 0
+	andi.	r8, r11, MSR_EE
 BEGIN_FTR_SECTION
-	mfspr	r8,SPRN_LPCR
-	ori	r8,r8,LPCR_MER
-	mtspr	SPRN_LPCR,r8
+	mfspr	r8, SPRN_LPCR
+	/* Insert EXTERNAL_LEVEL bit into LPCR at the MER bit position */
+	rldimi	r8, r0, LPCR_MER_SH, 63 - LPCR_MER_SH
+	mtspr	SPRN_LPCR, r8
 	isync
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
 	beq	5f
-	li	r0,BOOK3S_INTERRUPT_EXTERNAL
-12:	mr	r6,r10
+	li	r0, BOOK3S_INTERRUPT_EXTERNAL
+	bne	cr1, 12f
+	mfspr	r0, SPRN_DEC
+	cmpwi	r0, 0
+	li	r0, BOOK3S_INTERRUPT_DECREMENTER
+	bge	5f
+
+12:	mtspr	SPRN_SRR0, r10
 	mr	r10,r0
-	mr	r7,r11
+	mtspr	SPRN_SRR1, r11
 	li	r11,(MSR_ME << 1) | 1	/* synthesize MSR_SF | MSR_ME */
 	rotldi	r11,r11,63
-	b	5f
-11:	beq	5f
-	mfspr	r0,SPRN_DEC
-	cmpwi	r0,0
-	li	r0,BOOK3S_INTERRUPT_DECREMENTER
-	blt	12b
-
-	/* Move SRR0 and SRR1 into the respective regs */
-5:	mtspr	SPRN_SRR0, r6
-	mtspr	SPRN_SRR1, r7
+5:
 
 /*
  * Required state:
@@ -1047,39 +1003,19 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_206)
 	/* External interrupt, first check for host_ipi. If this is
 	 * set, we know the host wants us out so let's do it now
 	 */
-do_ext_interrupt:
 	bl	kvmppc_read_intr
 	cmpdi	r3, 0
 	bgt	ext_interrupt_to_host
 
-	/* Allright, looks like an IPI for the guest, we need to set MER */
 	/* Check if any CPU is heading out to the host, if so head out too */
 	ld	r5, HSTATE_KVM_VCORE(r13)
 	lwz	r0, VCORE_ENTRY_EXIT(r5)
 	cmpwi	r0, 0x100
 	bge	ext_interrupt_to_host
 
-	/* See if there is a pending interrupt for the guest */
-	mfspr	r8, SPRN_LPCR
-	ld	r0, VCPU_PENDING_EXC(r9)
-	/* Insert EXTERNAL_LEVEL bit into LPCR at the MER bit position */
-	rldicl.	r0, r0, 64 - BOOK3S_IRQPRIO_EXTERNAL_LEVEL, 63
-	rldimi	r8, r0, LPCR_MER_SH, 63 - LPCR_MER_SH
-	beq	2f
-
-	/* And if the guest EE is set, we can deliver immediately, else
-	 * we return to the guest with MER set
-	 */
-	andi.	r0, r11, MSR_EE
-	beq	2f
-	mtspr	SPRN_SRR0, r10
-	mtspr	SPRN_SRR1, r11
-	li	r10, BOOK3S_INTERRUPT_EXTERNAL
-	li	r11, (MSR_ME << 1) | 1	/* synthesize MSR_SF | MSR_ME */
-	rotldi	r11, r11, 63
-2:	mr	r4, r9
-	mtspr	SPRN_LPCR, r8
-	b	fast_guest_return
+	/* Return to guest after delivering any pending interrupt */
+	mr	r4, r9
+	b	deliver_guest_interrupt
 
 ext_interrupt_to_host:
 
@@ -1887,7 +1823,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_206)
 	stb	r0,HSTATE_NAPPING(r13)
 	/* order napping_threads update vs testing entry_exit_count */
 	lwsync
-	mr	r4,r3
 	lwz	r7,VCORE_ENTRY_EXIT(r5)
 	cmpwi	r7,0x100
 	bge	33f		/* another thread already exiting */
@@ -1940,6 +1875,11 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_206)
 	nap
 	b	.
 
+33:	mr	r4, r3
+	li	r3, 0
+	li	r12, 0
+	b	34f
+
 kvm_end_cede:
 	/* get vcpu pointer */
 	ld	r4, HSTATE_KVM_VCPU(r13)
@@ -1969,12 +1909,15 @@ kvm_end_cede:
 	ld	r29, VCPU_GPR(R29)(r4)
 	ld	r30, VCPU_GPR(R30)(r4)
 	ld	r31, VCPU_GPR(R31)(r4)
+ 
+	/* Check the wake reason in SRR1 to see why we got here */
+	bl	kvmppc_check_wake_reason
 
 	/* clear our bit in vcore->napping_threads */
-33:	ld	r5,HSTATE_KVM_VCORE(r13)
-	lbz	r3,HSTATE_PTID(r13)
+34:	ld	r5,HSTATE_KVM_VCORE(r13)
+	lbz	r7,HSTATE_PTID(r13)
 	li	r0,1
-	sld	r0,r0,r3
+	sld	r0,r0,r7
 	addi	r6,r5,VCORE_NAPPING_THREADS
 32:	lwarx	r7,0,r6
 	andc	r7,r7,r0
@@ -1983,23 +1926,18 @@ kvm_end_cede:
 	li	r0,0
 	stb	r0,HSTATE_NAPPING(r13)
 
-	/* Check the wake reason in SRR1 to see why we got here */
-	mfspr	r3, SPRN_SRR1
-	rlwinm	r3, r3, 44-31, 0x7	/* extract wake reason field */
-	cmpwi	r3, 4			/* was it an external interrupt? */
-	li	r12, BOOK3S_INTERRUPT_EXTERNAL
+	/* See if the wake reason means we need to exit */
+	stw	r12, VCPU_TRAP(r4)
 	mr	r9, r4
-	ld	r10, VCPU_PC(r9)
-	ld	r11, VCPU_MSR(r9)
-	beq	do_ext_interrupt	/* if so */
+	cmpdi	r3, 0
+	bgt	guest_exit_cont
 
 	/* see if any other thread is already exiting */
 	lwz	r0,VCORE_ENTRY_EXIT(r5)
 	cmpwi	r0,0x100
-	blt	kvmppc_cede_reentry	/* if not go back to guest */
+	bge	guest_exit_cont
 
-	/* some threads are exiting, so go to the guest exit path */
-	b	hcall_real_fallback
+	b	kvmppc_cede_reentry	/* if not go back to guest */
 
 	/* cede when already previously prodded case */
 kvm_cede_prodded:
@@ -2029,6 +1967,29 @@ machine_check_realmode:
 	rotldi	r11, r11, 63
 	b	fast_interrupt_c_return
 
+/*
+ * Check the reason we woke from nap, and take appropriate action.
+ * Returns:
+ *	0 if nothing needs to be done
+ *	1 if something happened that needs to be handled by the host
+ *	-1 if there was a guest wakeup (IPI)
+ *
+ * Also sets r12 to the interrupt vector for any interrupt that needs
+ * to be handled now by the host (0x500 for external interrupt), or zero.
+ */
+kvmppc_check_wake_reason:
+	mfspr	r6, SPRN_SRR1
+	rlwinm	r6, r6, 44-31, 0x7	/* extract wake reason field */
+	cmpwi	r6, 4			/* was it an external interrupt? */
+	li	r12, BOOK3S_INTERRUPT_EXTERNAL
+	beq	kvmppc_read_intr	/* if so, see what it was */
+	li	r3, 0
+	li	r12, 0
+	cmpwi	r6, 6			/* was it the decrementer? */
+	beq	0f
+	li	r3, 1			/* anything else, return 1 */
+0:	blr
+
 /*
  * Determine what sort of external interrupt is pending (if any).
  * Returns:
@@ -2060,7 +2021,6 @@ kvmppc_read_intr:
 	 * interrupts directly to the guest
 	 */
 	cmpwi	r3, XICS_IPI		/* if there is, is it an IPI? */
-	li	r3, 1
 	bne	42f
 
 	/* It's an IPI, clear the MFRR and EOI it */
@@ -2086,12 +2046,14 @@ kvmppc_read_intr:
 	 * before exit, it will be picked up by the host ICP driver
 	 */
 	stw	r0, HSTATE_SAVED_XIRR(r13)
+	li	r3, 1
 	b	1b
 
 43:	/* We raced with the host, we need to resend that IPI, bummer */
 	li	r0, IPI_PRIORITY
 	stbcix	r0, r6, r8		/* set the IPI */
 	sync
+	li	r3, 1
 	b	1b
 
 /*