Revert "KVM: PPC: Book3S HV: POWER9 does not require secondary thread management"

This reverts commit 94a04bc2.

In order to run HPT guests on a radix POWER9 host, we will have to run
the host in single-threaded mode, because POWER9 processors do not
currently support running some threads of a core in HPT mode while
others are in radix mode ("mixed mode").

That means that we will need the same mechanisms that are used on
POWER8 to make the secondary threads available to KVM, which were
disabled on POWER9 by commit 94a04bc2.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/kvm_book3s_asm.h

@@ -104,10 +104,6 @@ struct kvmppc_host_state {
 	u8 napping;
 
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-	/*
-	 * hwthread_req/hwthread_state pair is used to pull sibling threads
-	 * out of guest on pre-ISAv3.0B CPUs where threads share MMU.
-	 */
 	u8 hwthread_req;
 	u8 hwthread_state;
 	u8 host_ipi;

arch/powerpc/kernel/idle_book3s.S

@@ -319,20 +319,13 @@ enter_winkle:
 /*
  * r3 - PSSCR value corresponding to the requested stop state.
  */
+power_enter_stop:
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-power_enter_stop_kvm_rm:
-	/*
-	 * This is currently unused because POWER9 KVM does not have to
-	 * gather secondary threads into sibling mode, but the code is
-	 * here in case that function is required.
-	 *
-	 * Tell KVM we're entering idle.
-	 */
+	/* Tell KVM we're entering idle */
 	li	r4,KVM_HWTHREAD_IN_IDLE
 	/* DO THIS IN REAL MODE!  See comment above. */
 	stb	r4,HSTATE_HWTHREAD_STATE(r13)
 #endif
-power_enter_stop:
 /*
  * Check if we are executing the lite variant with ESL=EC=0
  */
@@ -496,18 +489,6 @@ pnv_powersave_wakeup_mce:
 
 	b	pnv_powersave_wakeup
 
-#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-kvm_start_guest_check:
-	li	r0,KVM_HWTHREAD_IN_KERNEL
-	stb	r0,HSTATE_HWTHREAD_STATE(r13)
-	/* Order setting hwthread_state vs. testing hwthread_req */
-	sync
-	lbz	r0,HSTATE_HWTHREAD_REQ(r13)
-	cmpwi	r0,0
-	beqlr
-	b	kvm_start_guest
-#endif
-
 /*
  * Called from reset vector for powersave wakeups.
  * cr3 - set to gt if waking up with partial/complete hypervisor state loss
@@ -532,9 +513,15 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
 	mr	r3,r12
 
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-BEGIN_FTR_SECTION
-	bl	kvm_start_guest_check
-END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
+	li	r0,KVM_HWTHREAD_IN_KERNEL
+	stb	r0,HSTATE_HWTHREAD_STATE(r13)
+	/* Order setting hwthread_state vs. testing hwthread_req */
+	sync
+	lbz	r0,HSTATE_HWTHREAD_REQ(r13)
+	cmpwi	r0,0
+	beq	1f
+	b	kvm_start_guest
+1:
 #endif
 
 	/* Return SRR1 from power7_nap() */

arch/powerpc/kvm/book3s_hv.c

@@ -2117,15 +2117,6 @@ static int kvmppc_grab_hwthread(int cpu)
 	struct paca_struct *tpaca;
 	long timeout = 10000;
 
-	/*
-	 * ISA v3.0 idle routines do not set hwthread_state or test
-	 * hwthread_req, so they can not grab idle threads.
-	 */
-	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
-		WARN(1, "KVM: can not control sibling threads\n");
-		return -EBUSY;
-	}
-
 	tpaca = &paca[cpu];
 
 	/* Ensure the thread won't go into the kernel if it wakes */
@@ -2160,12 +2151,10 @@ static void kvmppc_release_hwthread(int cpu)
 	struct paca_struct *tpaca;
 
 	tpaca = &paca[cpu];
+	tpaca->kvm_hstate.hwthread_req = 0;
 	tpaca->kvm_hstate.kvm_vcpu = NULL;
 	tpaca->kvm_hstate.kvm_vcore = NULL;
 	tpaca->kvm_hstate.kvm_split_mode = NULL;
-	if (!cpu_has_feature(CPU_FTR_ARCH_300))
-		tpaca->kvm_hstate.hwthread_req = 0;
-
 }
 
 static void radix_flush_cpu(struct kvm *kvm, int cpu, struct kvm_vcpu *vcpu)

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -149,11 +149,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 	subf	r4, r4, r3
 	mtspr	SPRN_DEC, r4
 
-BEGIN_FTR_SECTION
 	/* hwthread_req may have got set by cede or no vcpu, so clear it */
 	li	r0, 0
 	stb	r0, HSTATE_HWTHREAD_REQ(r13)
-END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
 
 	/*
 	 * For external interrupts we need to call the Linux
@@ -316,7 +314,6 @@ kvm_novcpu_exit:
  * Relocation is off and most register values are lost.
  * r13 points to the PACA.
  * r3 contains the SRR1 wakeup value, SRR1 is trashed.
- * This is not used by ISAv3.0B processors.
  */
 	.globl	kvm_start_guest
 kvm_start_guest:
@@ -435,9 +432,6 @@ kvm_secondary_got_guest:
  * While waiting we also need to check if we get given a vcpu to run.
  */
 kvm_no_guest:
-BEGIN_FTR_SECTION
-	twi	31,0,0
-END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 	lbz	r3, HSTATE_HWTHREAD_REQ(r13)
 	cmpwi	r3, 0
 	bne	53f
@@ -2531,10 +2525,8 @@ kvm_do_nap:
 	clrrdi	r0, r0, 1
 	mtspr	SPRN_CTRLT, r0
 
-BEGIN_FTR_SECTION
 	li	r0,1
 	stb	r0,HSTATE_HWTHREAD_REQ(r13)
-END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
 	mfspr	r5,SPRN_LPCR
 	ori	r5,r5,LPCR_PECE0 | LPCR_PECE1
 BEGIN_FTR_SECTION