KVM: PPC: Book3S HV: Move interrupt delivery on guest entry to C code

This is based on a patch by Suraj Jitindar Singh.

This moves the code in book3s_hv_rmhandlers.S that generates an
external, decrementer or privileged doorbell interrupt just before
entering the guest to C code in book3s_hv_builtin.c.  This is to
make future maintenance and modification easier.  The algorithm
expressed in the C code is almost identical to the previous
algorithm.
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/kvm_ppc.h

@@ -650,6 +650,7 @@ int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
                     unsigned long mfrr);
 int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr);
 int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr);
+void kvmppc_guest_entry_inject_int(struct kvm_vcpu *vcpu);
 
 /*
  * Host-side operations we want to set up while running in real

arch/powerpc/kvm/book3s_hv.c

@@ -730,8 +730,7 @@ static bool kvmppc_doorbell_pending(struct kvm_vcpu *vcpu)
 	/*
 	 * Ensure that the read of vcore->dpdes comes after the read
 	 * of vcpu->doorbell_request.  This barrier matches the
-	 * lwsync in book3s_hv_rmhandlers.S just before the
-	 * fast_guest_return label.
+	 * smb_wmb() in kvmppc_guest_entry_inject().
 	 */
 	smp_rmb();
 	vc = vcpu->arch.vcore;

arch/powerpc/kvm/book3s_hv_builtin.c

@@ -729,3 +729,51 @@ void kvmhv_p9_restore_lpcr(struct kvm_split_mode *sip)
 	smp_mb();
 	local_paca->kvm_hstate.kvm_split_mode = NULL;
 }
+
+/*
+ * Is there a PRIV_DOORBELL pending for the guest (on POWER9)?
+ * Can we inject a Decrementer or a External interrupt?
+ */
+void kvmppc_guest_entry_inject_int(struct kvm_vcpu *vcpu)
+{
+	int ext;
+	unsigned long vec = 0;
+	unsigned long lpcr;
+
+	/* Insert EXTERNAL bit into LPCR at the MER bit position */
+	ext = (vcpu->arch.pending_exceptions >> BOOK3S_IRQPRIO_EXTERNAL) & 1;
+	lpcr = mfspr(SPRN_LPCR);
+	lpcr |= ext << LPCR_MER_SH;
+	mtspr(SPRN_LPCR, lpcr);
+	isync();
+
+	if (vcpu->arch.shregs.msr & MSR_EE) {
+		if (ext) {
+			vec = BOOK3S_INTERRUPT_EXTERNAL;
+		} else {
+			long int dec = mfspr(SPRN_DEC);
+			if (!(lpcr & LPCR_LD))
+				dec = (int) dec;
+			if (dec < 0)
+				vec = BOOK3S_INTERRUPT_DECREMENTER;
+		}
+	}
+	if (vec) {
+		unsigned long msr, old_msr = vcpu->arch.shregs.msr;
+
+		kvmppc_set_srr0(vcpu, kvmppc_get_pc(vcpu));
+		kvmppc_set_srr1(vcpu, old_msr);
+		kvmppc_set_pc(vcpu, vec);
+		msr = vcpu->arch.intr_msr;
+		if (MSR_TM_ACTIVE(old_msr))
+			msr |= MSR_TS_S;
+		vcpu->arch.shregs.msr = msr;
+	}
+
+	if (vcpu->arch.doorbell_request) {
+		mtspr(SPRN_DPDES, 1);
+		vcpu->arch.vcore->dpdes = 1;
+		smp_wmb();
+		vcpu->arch.doorbell_request = 0;
+	}
+}

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -1101,13 +1101,20 @@ no_xive:
 #endif /* CONFIG_KVM_XICS */
 
 deliver_guest_interrupt:
-	ld	r6, VCPU_CTR(r4)
-	ld	r7, VCPU_XER(r4)
-
-	mtctr	r6
-	mtxer	r7
-
 kvmppc_cede_reentry:		/* r4 = vcpu, r13 = paca */
+	/* Check if we can deliver an external or decrementer interrupt now */
+	ld	r0, VCPU_PENDING_EXC(r4)
+BEGIN_FTR_SECTION
+	/* On POWER9, also check for emulated doorbell interrupt */
+	lbz	r3, VCPU_DBELL_REQ(r4)
+	or	r0, r0, r3
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
+	cmpdi	r0, 0
+	beq	71f
+	mr	r3, r4
+	bl	kvmppc_guest_entry_inject_int
+	ld	r4, HSTATE_KVM_VCPU(r13)
+71:
 	ld	r10, VCPU_PC(r4)
 	ld	r11, VCPU_MSR(r4)
 	ld	r6, VCPU_SRR0(r4)
@@ -1120,53 +1127,10 @@ kvmppc_cede_reentry:		/* r4 = vcpu, r13 = paca */
 	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)
-	rldicl	r0, r0, 64 - BOOK3S_IRQPRIO_EXTERNAL, 63
-	cmpdi	cr1, r0, 0
-	andi.	r8, r11, MSR_EE
-	mfspr	r8, SPRN_LPCR
-	/* Insert EXTERNAL bit into LPCR at the MER bit position */
-	rldimi	r8, r0, LPCR_MER_SH, 63 - LPCR_MER_SH
-	mtspr	SPRN_LPCR, r8
-	isync
-	beq	5f
-	li	r0, BOOK3S_INTERRUPT_EXTERNAL
-	bne	cr1, 12f
-	mfspr	r0, SPRN_DEC
-BEGIN_FTR_SECTION
-	/* On POWER9 check whether the guest has large decrementer enabled */
-	andis.	r8, r8, LPCR_LD@h
-	bne	15f
-END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
-	extsw	r0, r0
-15:	cmpdi	r0, 0
-	li	r0, BOOK3S_INTERRUPT_DECREMENTER
-	bge	5f
-
-12:	mtspr	SPRN_SRR0, r10
-	mr	r10,r0
-	mtspr	SPRN_SRR1, r11
-	mr	r9, r4
-	bl	kvmppc_msr_interrupt
-5:
-BEGIN_FTR_SECTION
-	b	fast_guest_return
-END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
-	/* On POWER9, check for pending doorbell requests */
-	lbz	r0, VCPU_DBELL_REQ(r4)
-	cmpwi	r0, 0
-	beq	fast_guest_return
-	ld	r5, HSTATE_KVM_VCORE(r13)
-	/* Set DPDES register so the CPU will take a doorbell interrupt */
-	li	r0, 1
-	mtspr	SPRN_DPDES, r0
-	std	r0, VCORE_DPDES(r5)
-	/* Make sure other cpus see vcore->dpdes set before dbell req clear */
-	lwsync
-	/* Clear the pending doorbell request */
-	li	r0, 0
-	stb	r0, VCPU_DBELL_REQ(r4)
+	ld	r6, VCPU_CTR(r4)
+	ld	r7, VCPU_XER(r4)
+	mtctr	r6
+	mtxer	r7
 
 /*
  * Required state: