KVM: PPC: Book3S HV: Add support for guest Program Priority Register

POWER7 and later IBM server processors have a register called the
Program Priority Register (PPR), which controls the priority of
each hardware CPU SMT thread, and affects how fast it runs compared
to other SMT threads.  This priority can be controlled by writing to
the PPR or by use of a set of instructions of the form or rN,rN,rN
which are otherwise no-ops but have been defined to set the priority
to particular levels.

This adds code to context switch the PPR when entering and exiting
guests and to make the PPR value accessible through the SET/GET_ONE_REG
interface.  When entering the guest, we set the PPR as late as
possible, because if we are setting a low thread priority it will
make the code run slowly from that point on.  Similarly, the
first-level interrupt handlers save the PPR value in the PACA very
early on, and set the thread priority to the medium level, so that
the interrupt handling code runs at a reasonable speed.

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

Documentation/virtual/kvm/api.txt

@@ -1836,6 +1836,7 @@ registers, find a list below:
   PPC   | KVM_REG_PPC_ACOP	| 64
   PPC   | KVM_REG_PPC_VRSAVE	| 32
   PPC   | KVM_REG_PPC_LPCR	| 64
+  PPC   | KVM_REG_PPC_PPR	| 64
   PPC   | KVM_REG_PPC_TM_GPR0	| 64
           ...
   PPC   | KVM_REG_PPC_TM_GPR31	| 64

arch/powerpc/include/asm/exception-64s.h

@@ -204,6 +204,10 @@ do_kvm_##n:								\
 	ld	r10,area+EX_CFAR(r13);					\
 	std	r10,HSTATE_CFAR(r13);					\
 	END_FTR_SECTION_NESTED(CPU_FTR_CFAR,CPU_FTR_CFAR,947);		\
+	BEGIN_FTR_SECTION_NESTED(948)					\
+	ld	r10,area+EX_PPR(r13);					\
+	std	r10,HSTATE_PPR(r13);					\
+	END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948);	\
 	ld	r10,area+EX_R10(r13);					\
 	stw	r9,HSTATE_SCRATCH1(r13);				\
 	ld	r9,area+EX_R9(r13);					\
@@ -217,6 +221,10 @@ do_kvm_##n:								\
 	ld	r10,area+EX_R10(r13);					\
 	beq	89f;							\
 	stw	r9,HSTATE_SCRATCH1(r13);			\
+	BEGIN_FTR_SECTION_NESTED(948)					\
+	ld	r9,area+EX_PPR(r13);					\
+	std	r9,HSTATE_PPR(r13);					\
+	END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948);	\
 	ld	r9,area+EX_R9(r13);					\
 	std	r12,HSTATE_SCRATCH0(r13);			\
 	li	r12,n;							\

arch/powerpc/include/asm/kvm_book3s_asm.h

@@ -101,6 +101,7 @@ struct kvmppc_host_state {
 #endif
 #ifdef CONFIG_PPC_BOOK3S_64
 	u64 cfar;
+	u64 ppr;
 #endif
 };
 

arch/powerpc/include/asm/kvm_host.h

@@ -460,6 +460,7 @@ struct kvm_vcpu_arch {
 	u32 ctrl;
 	ulong dabr;
 	ulong cfar;
+	ulong ppr;
 #endif
 	u32 vrsave; /* also USPRG0 */
 	u32 mmucr;

arch/powerpc/include/uapi/asm/kvm.h

@@ -534,6 +534,7 @@ struct kvm_get_htab_header {
 
 #define KVM_REG_PPC_VRSAVE	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0xb4)
 #define KVM_REG_PPC_LPCR	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0xb5)
+#define KVM_REG_PPC_PPR		(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xb6)
 
 /* Transactional Memory checkpointed state:
  * This is all GPRs, all VSX regs and a subset of SPRs

arch/powerpc/kernel/asm-offsets.c

@@ -519,6 +519,7 @@ int main(void)
 	DEFINE(VCPU_TRAP, offsetof(struct kvm_vcpu, arch.trap));
 	DEFINE(VCPU_PTID, offsetof(struct kvm_vcpu, arch.ptid));
 	DEFINE(VCPU_CFAR, offsetof(struct kvm_vcpu, arch.cfar));
+	DEFINE(VCPU_PPR, offsetof(struct kvm_vcpu, arch.ppr));
 	DEFINE(VCORE_ENTRY_EXIT, offsetof(struct kvmppc_vcore, entry_exit_count));
 	DEFINE(VCORE_NAP_COUNT, offsetof(struct kvmppc_vcore, nap_count));
 	DEFINE(VCORE_IN_GUEST, offsetof(struct kvmppc_vcore, in_guest));
@@ -604,6 +605,7 @@ int main(void)
 
 #ifdef CONFIG_PPC_BOOK3S_64
 	HSTATE_FIELD(HSTATE_CFAR, cfar);
+	HSTATE_FIELD(HSTATE_PPR, ppr);
 #endif /* CONFIG_PPC_BOOK3S_64 */
 
 #else /* CONFIG_PPC_BOOK3S */

arch/powerpc/kvm/book3s_hv.c

@@ -823,6 +823,9 @@ int kvmppc_get_one_reg(struct kvm_vcpu *vcpu, u64 id, union kvmppc_one_reg *val)
 	case KVM_REG_PPC_LPCR:
 		*val = get_reg_val(id, vcpu->arch.vcore->lpcr);
 		break;
+	case KVM_REG_PPC_PPR:
+		*val = get_reg_val(id, vcpu->arch.ppr);
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -930,6 +933,9 @@ int kvmppc_set_one_reg(struct kvm_vcpu *vcpu, u64 id, union kvmppc_one_reg *val)
 	case KVM_REG_PPC_LPCR:
 		kvmppc_set_lpcr(vcpu, set_reg_val(id, *val));
 		break;
+	case KVM_REG_PPC_PPR:
+		vcpu->arch.ppr = set_reg_val(id, *val);
+		break;
 	default:
 		r = -EINVAL;
 		break;

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -717,13 +717,15 @@ BEGIN_FTR_SECTION
 	ld	r5, VCPU_CFAR(r4)
 	mtspr	SPRN_CFAR, r5
 END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
+BEGIN_FTR_SECTION
+	ld	r0, VCPU_PPR(r4)
+END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 
 	ld	r5, VCPU_LR(r4)
 	lwz	r6, VCPU_CR(r4)
 	mtlr	r5
 	mtcr	r6
 
-	ld	r0, VCPU_GPR(R0)(r4)
 	ld	r1, VCPU_GPR(R1)(r4)
 	ld	r2, VCPU_GPR(R2)(r4)
 	ld	r3, VCPU_GPR(R3)(r4)
@@ -737,6 +739,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 	ld	r12, VCPU_GPR(R12)(r4)
 	ld	r13, VCPU_GPR(R13)(r4)
 
+BEGIN_FTR_SECTION
+	mtspr	SPRN_PPR, r0
+END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
+	ld	r0, VCPU_GPR(R0)(r4)
 	ld	r4, VCPU_GPR(R4)(r4)
 
 	hrfid
@@ -787,6 +793,10 @@ BEGIN_FTR_SECTION
 	ld	r3, HSTATE_CFAR(r13)
 	std	r3, VCPU_CFAR(r9)
 END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
+BEGIN_FTR_SECTION
+	ld	r4, HSTATE_PPR(r13)
+	std	r4, VCPU_PPR(r9)
+END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 
 	/* Restore R1/R2 so we can handle faults */
 	ld	r1, HSTATE_HOST_R1(r13)