Commit 94a04bc2 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

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



POWER9 CPUs have independent MMU contexts per thread, so KVM does not
need to quiesce secondary threads, so the hwthread_req/hwthread_state
protocol does not have to be used. So patch it away on POWER9, and patch
away the branch from the Linux idle wakeup to kvm_start_guest that is
never used.

Add a warning and error out of kvmppc_grab_hwthread in case it is ever
called on POWER9.

This avoids a hwsync in the idle wakeup path on POWER9.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Acked-by: default avatarPaul Mackerras <paulus@ozlabs.org>
[mpe: Use WARN(...) instead of WARN_ON()/pr_err(...)]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 94171b19

arch/powerpc/include/asm/kvm_book3s_asm.h

+4 −0
Original line number Diff line number Diff line
@@ -104,6 +104,10 @@ 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

+24 −11
Original line number Diff line number Diff line
@@ -242,13 +242,20 @@ enter_winkle: 
/*

 * r3 - PSSCR value corresponding to the requested stop state.

 */

power_enter_stop:

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

	/* Tell KVM we're entering idle */

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.

	 */

	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

 */
@@ -411,6 +418,18 @@ 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
@@ -435,15 +454,9 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300) 
	mr	r3,r12



#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

	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:

BEGIN_FTR_SECTION

	bl	kvm_start_guest_check

END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)

#endif



	/* Return SRR1 from power7_nap() */

arch/powerpc/kvm/book3s_hv.c

+12 −1
Original line number Diff line number Diff line
@@ -2111,6 +2111,15 @@ 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 */
@@ -2145,10 +2154,12 @@ 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

+8 −0
Original line number Diff line number Diff line
@@ -149,9 +149,11 @@ 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
@@ -314,6 +316,7 @@ 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:
@@ -432,6 +435,9 @@ 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
@@ -2466,8 +2472,10 @@ 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

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