powerpc/64s: Keep AMOR SPR a constant ~0 at runtime

This register controls supervisor SPR modifications, and as such is only
relevant for KVM. KVM always sets AMOR to ~0 on guest entry, and never
restores it coming back out to the host, so it can be kept constant and
avoid the mtSPR in KVM guest entry.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-10-npiggin@gmail.com

arch/powerpc/kernel/cpu_setup_power.c

@@ -137,6 +137,7 @@ void __setup_cpu_power7(unsigned long offset, struct cpu_spec *t)
 		return;
 
 	mtspr(SPRN_LPID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA206(mfspr(SPRN_LPCR), LPCR_LPES1 >> LPCR_LPES_SH);
 }
@@ -150,6 +151,7 @@ void __restore_cpu_power7(void)
 		return;
 
 	mtspr(SPRN_LPID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA206(mfspr(SPRN_LPCR), LPCR_LPES1 >> LPCR_LPES_SH);
 }
@@ -164,6 +166,7 @@ void __setup_cpu_power8(unsigned long offset, struct cpu_spec *t)
 		return;
 
 	mtspr(SPRN_LPID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA206(mfspr(SPRN_LPCR) | LPCR_PECEDH, 0); /* LPES = 0 */
 	init_HFSCR();
@@ -184,6 +187,7 @@ void __restore_cpu_power8(void)
 		return;
 
 	mtspr(SPRN_LPID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA206(mfspr(SPRN_LPCR) | LPCR_PECEDH, 0); /* LPES = 0 */
 	init_HFSCR();
@@ -202,6 +206,7 @@ void __setup_cpu_power9(unsigned long offset, struct cpu_spec *t)
 	mtspr(SPRN_PSSCR, 0);
 	mtspr(SPRN_LPID, 0);
 	mtspr(SPRN_PID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA300((mfspr(SPRN_LPCR) | LPCR_PECEDH | LPCR_PECE_HVEE |\
 			 LPCR_HVICE | LPCR_HEIC) & ~(LPCR_UPRT | LPCR_HR), 0);
@@ -223,6 +228,7 @@ void __restore_cpu_power9(void)
 	mtspr(SPRN_PSSCR, 0);
 	mtspr(SPRN_LPID, 0);
 	mtspr(SPRN_PID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA300((mfspr(SPRN_LPCR) | LPCR_PECEDH | LPCR_PECE_HVEE |\
 			 LPCR_HVICE | LPCR_HEIC) & ~(LPCR_UPRT | LPCR_HR), 0);
@@ -242,6 +248,7 @@ void __setup_cpu_power10(unsigned long offset, struct cpu_spec *t)
 	mtspr(SPRN_PSSCR, 0);
 	mtspr(SPRN_LPID, 0);
 	mtspr(SPRN_PID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA300((mfspr(SPRN_LPCR) | LPCR_PECEDH | LPCR_PECE_HVEE |\
 			 LPCR_HVICE | LPCR_HEIC) & ~(LPCR_UPRT | LPCR_HR), 0);
@@ -264,6 +271,7 @@ void __restore_cpu_power10(void)
 	mtspr(SPRN_PSSCR, 0);
 	mtspr(SPRN_LPID, 0);
 	mtspr(SPRN_PID, 0);
+	mtspr(SPRN_AMOR, ~0);
 	mtspr(SPRN_PCR, PCR_MASK);
 	init_LPCR_ISA300((mfspr(SPRN_LPCR) | LPCR_PECEDH | LPCR_PECE_HVEE |\
 			 LPCR_HVICE | LPCR_HEIC) & ~(LPCR_UPRT | LPCR_HR), 0);

arch/powerpc/kernel/dt_cpu_ftrs.c

@@ -80,6 +80,7 @@ static void __restore_cpu_cpufeatures(void)
 	mtspr(SPRN_LPCR, system_registers.lpcr);
 	if (hv_mode) {
 		mtspr(SPRN_LPID, 0);
+		mtspr(SPRN_AMOR, ~0);
 		mtspr(SPRN_HFSCR, system_registers.hfscr);
 		mtspr(SPRN_PCR, system_registers.pcr);
 	}
@@ -216,6 +217,7 @@ static int __init feat_enable_hv(struct dt_cpu_feature *f)
 	}
 
 	mtspr(SPRN_LPID, 0);
+	mtspr(SPRN_AMOR, ~0);
 
 	lpcr = mfspr(SPRN_LPCR);
 	lpcr &=  ~LPCR_LPES0; /* HV external interrupts */

arch/powerpc/kvm/book3s_hv_p9_entry.c

@@ -286,8 +286,6 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
 	mtspr(SPRN_SPRG2, vcpu->arch.shregs.sprg2);
 	mtspr(SPRN_SPRG3, vcpu->arch.shregs.sprg3);
 
-	mtspr(SPRN_AMOR, ~0UL);
-
 	local_paca->kvm_hstate.in_guest = KVM_GUEST_MODE_HV_P9;
 
 	/*

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -778,10 +778,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 	/* Restore AMR and UAMOR, set AMOR to all 1s */
 	ld	r5,VCPU_AMR(r4)
 	ld	r6,VCPU_UAMOR(r4)
-	li	r7,-1
 	mtspr	SPRN_AMR,r5
 	mtspr	SPRN_UAMOR,r6
-	mtspr	SPRN_AMOR,r7
 
 	/* Restore state of CTRL run bit; assume 1 on entry */
 	lwz	r5,VCPU_CTRL(r4)

arch/powerpc/mm/book3s64/radix_pgtable.c

@@ -572,18 +572,6 @@ void __init radix__early_init_devtree(void)
 	return;
 }
 
-static void radix_init_amor(void)
-{
-	/*
-	* In HV mode, we init AMOR (Authority Mask Override Register) so that
-	* the hypervisor and guest can setup IAMR (Instruction Authority Mask
-	* Register), enable key 0 and set it to 1.
-	*
-	* AMOR = 0b1100 .... 0000 (Mask for key 0 is 11)
-	*/
-	mtspr(SPRN_AMOR, (3ul << 62));
-}
-
 void __init radix__early_init_mmu(void)
 {
 	unsigned long lpcr;
@@ -644,7 +632,6 @@ void __init radix__early_init_mmu(void)
 		lpcr = mfspr(SPRN_LPCR);
 		mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);
 		radix_init_partition_table();
-		radix_init_amor();
 	} else {
 		radix_init_pseries();
 	}
@@ -668,8 +655,6 @@ void radix__early_init_mmu_secondary(void)
 
 		set_ptcr_when_no_uv(__pa(partition_tb) |
 				    (PATB_SIZE_SHIFT - 12));
-
-		radix_init_amor();
 	}
 
 	radix__switch_mmu_context(NULL, &init_mm);

arch/powerpc/platforms/powernv/idle.c

@@ -306,8 +306,8 @@ struct p7_sprs {
 	/* per thread SPRs that get lost in shallow states */
 	u64 amr;
 	u64 iamr;
-	u64 amor;
 	u64 uamor;
+	/* amor is restored to constant ~0 */
 };
 
 static unsigned long power7_idle_insn(unsigned long type)
@@ -378,7 +378,6 @@ static unsigned long power7_idle_insn(unsigned long type)
 	if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
 		sprs.amr	= mfspr(SPRN_AMR);
 		sprs.iamr	= mfspr(SPRN_IAMR);
-		sprs.amor	= mfspr(SPRN_AMOR);
 		sprs.uamor	= mfspr(SPRN_UAMOR);
 	}
 
@@ -397,7 +396,7 @@ static unsigned long power7_idle_insn(unsigned long type)
 			 */
 			mtspr(SPRN_AMR,		sprs.amr);
 			mtspr(SPRN_IAMR,	sprs.iamr);
-			mtspr(SPRN_AMOR,	sprs.amor);
+			mtspr(SPRN_AMOR,	~0);
 			mtspr(SPRN_UAMOR,	sprs.uamor);
 		}
 	}
@@ -686,7 +685,6 @@ static unsigned long power9_idle_stop(unsigned long psscr)
 
 	sprs.amr	= mfspr(SPRN_AMR);
 	sprs.iamr	= mfspr(SPRN_IAMR);
-	sprs.amor	= mfspr(SPRN_AMOR);
 	sprs.uamor	= mfspr(SPRN_UAMOR);
 
 	srr1 = isa300_idle_stop_mayloss(psscr);		/* go idle */
@@ -707,7 +705,7 @@ static unsigned long power9_idle_stop(unsigned long psscr)
 		 */
 		mtspr(SPRN_AMR,		sprs.amr);
 		mtspr(SPRN_IAMR,	sprs.iamr);
-		mtspr(SPRN_AMOR,	sprs.amor);
+		mtspr(SPRN_AMOR,	~0);
 		mtspr(SPRN_UAMOR,	sprs.uamor);
 
 		/*