KVM: PPC: Book3S HV P9: Fixes for TM softpatch interrupt NIP

The softpatch interrupt sets HSRR0 to the faulting instruction +4, so
it should subtract 4 for the faulting instruction address in the case
it is a TM softpatch interrupt (the instruction was not executed) and
it was not emulated.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210811160134.904987-4-npiggin@gmail.com

arch/powerpc/kvm/book3s_hv_tm.c

@@ -46,6 +46,15 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 	u64 newmsr, bescr;
 	int ra, rs;
 
+	/*
+	 * The TM softpatch interrupt sets NIP to the instruction following
+	 * the faulting instruction, which is not executed. Rewind nip to the
+	 * faulting instruction so it looks like a normal synchronous
+	 * interrupt, then update nip in the places where the instruction is
+	 * emulated.
+	 */
+	vcpu->arch.regs.nip -= 4;
+
 	/*
 	 * rfid, rfebb, and mtmsrd encode bit 31 = 0 since it's a reserved bit
 	 * in these instructions, so masking bit 31 out doesn't change these
@@ -67,7 +76,7 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 			       (newmsr & MSR_TM)));
 		newmsr = sanitize_msr(newmsr);
 		vcpu->arch.shregs.msr = newmsr;
-		vcpu->arch.cfar = vcpu->arch.regs.nip - 4;
+		vcpu->arch.cfar = vcpu->arch.regs.nip;
 		vcpu->arch.regs.nip = vcpu->arch.shregs.srr0;
 		return RESUME_GUEST;
 
@@ -100,7 +109,7 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 		vcpu->arch.bescr = bescr;
 		msr = (msr & ~MSR_TS_MASK) | MSR_TS_T;
 		vcpu->arch.shregs.msr = msr;
-		vcpu->arch.cfar = vcpu->arch.regs.nip - 4;
+		vcpu->arch.cfar = vcpu->arch.regs.nip;
 		vcpu->arch.regs.nip = vcpu->arch.ebbrr;
 		return RESUME_GUEST;
 
@@ -116,6 +125,7 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 		newmsr = (newmsr & ~MSR_LE) | (msr & MSR_LE);
 		newmsr = sanitize_msr(newmsr);
 		vcpu->arch.shregs.msr = newmsr;
+		vcpu->arch.regs.nip += 4;
 		return RESUME_GUEST;
 
 	/* ignore bit 31, see comment above */
@@ -152,6 +162,7 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 				msr = (msr & ~MSR_TS_MASK) | MSR_TS_S;
 		}
 		vcpu->arch.shregs.msr = msr;
+		vcpu->arch.regs.nip += 4;
 		return RESUME_GUEST;
 
 	/* ignore bit 31, see comment above */
@@ -189,6 +200,7 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 		vcpu->arch.regs.ccr = (vcpu->arch.regs.ccr & 0x0fffffff) |
 			(((msr & MSR_TS_MASK) >> MSR_TS_S_LG) << 29);
 		vcpu->arch.shregs.msr &= ~MSR_TS_MASK;
+		vcpu->arch.regs.nip += 4;
 		return RESUME_GUEST;
 
 	/* ignore bit 31, see comment above */
@@ -220,6 +232,7 @@ int kvmhv_p9_tm_emulation(struct kvm_vcpu *vcpu)
 		vcpu->arch.regs.ccr = (vcpu->arch.regs.ccr & 0x0fffffff) |
 			(((msr & MSR_TS_MASK) >> MSR_TS_S_LG) << 29);
 		vcpu->arch.shregs.msr = msr | MSR_TS_S;
+		vcpu->arch.regs.nip += 4;
 		return RESUME_GUEST;
 	}