Commit 9a1e530b authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
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KVM: PPC: Book3S HV P9: Avoid SPR scoreboard stalls 



Avoid interleaving mfSPR and mtSPR to reduce SPR scoreboard stalls.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-26-npiggin@gmail.com
parent cb2553a0

arch/powerpc/kvm/book3s_hv.c

+4 −4
Original line number Diff line number Diff line
@@ -4321,10 +4321,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, 


	store_spr_state(vcpu);



	timer_rearm_host_dec(*tb);



	restore_p9_host_os_sprs(vcpu, &host_os_sprs);



	store_fp_state(&vcpu->arch.fp);

#ifdef CONFIG_ALTIVEC

	store_vr_state(&vcpu->arch.vr);
@@ -4339,6 +4335,10 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, 


	switch_pmu_to_host(vcpu, &host_os_sprs);



	timer_rearm_host_dec(*tb);



	restore_p9_host_os_sprs(vcpu, &host_os_sprs);



	vc->entry_exit_map = 0x101;

	vc->in_guest = 0;

arch/powerpc/kvm/book3s_hv_p9_entry.c

+11 −8
Original line number Diff line number Diff line
@@ -228,6 +228,9 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
		host_dawrx1 = mfspr(SPRN_DAWRX1);

	}



	local_paca->kvm_hstate.host_purr = mfspr(SPRN_PURR);

	local_paca->kvm_hstate.host_spurr = mfspr(SPRN_SPURR);



	if (vc->tb_offset) {

		u64 new_tb = *tb + vc->tb_offset;

		mtspr(SPRN_TBU40, new_tb);
@@ -244,8 +247,6 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
	mtspr(SPRN_DPDES, vc->dpdes);

	mtspr(SPRN_VTB, vc->vtb);



	local_paca->kvm_hstate.host_purr = mfspr(SPRN_PURR);

	local_paca->kvm_hstate.host_spurr = mfspr(SPRN_SPURR);

	mtspr(SPRN_PURR, vcpu->arch.purr);

	mtspr(SPRN_SPURR, vcpu->arch.spurr);
@@ -448,10 +449,8 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
	/* Advance host PURR/SPURR by the amount used by guest */

	purr = mfspr(SPRN_PURR);

	spurr = mfspr(SPRN_SPURR);

	mtspr(SPRN_PURR, local_paca->kvm_hstate.host_purr +

	      purr - vcpu->arch.purr);

	mtspr(SPRN_SPURR, local_paca->kvm_hstate.host_spurr +

	      spurr - vcpu->arch.spurr);

	local_paca->kvm_hstate.host_purr += purr - vcpu->arch.purr;

	local_paca->kvm_hstate.host_spurr += spurr - vcpu->arch.spurr;

	vcpu->arch.purr = purr;

	vcpu->arch.spurr = spurr;
@@ -464,6 +463,9 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
	vcpu->arch.shregs.sprg2 = mfspr(SPRN_SPRG2);

	vcpu->arch.shregs.sprg3 = mfspr(SPRN_SPRG3);



	vc->dpdes = mfspr(SPRN_DPDES);

	vc->vtb = mfspr(SPRN_VTB);



	dec = mfspr(SPRN_DEC);

	if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */

		dec = (s32) dec;
@@ -481,6 +483,9 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
		vc->tb_offset_applied = 0;

	}



	mtspr(SPRN_PURR, local_paca->kvm_hstate.host_purr);

	mtspr(SPRN_SPURR, local_paca->kvm_hstate.host_spurr);



	/* Preserve PSSCR[FAKE_SUSPEND] until we've called kvmppc_save_tm_hv */

	mtspr(SPRN_PSSCR, host_psscr |

	      (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
@@ -509,8 +514,6 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
	if (cpu_has_feature(CPU_FTR_ARCH_31))

		asm volatile(PPC_CP_ABORT);



	vc->dpdes = mfspr(SPRN_DPDES);

	vc->vtb = mfspr(SPRN_VTB);

	mtspr(SPRN_DPDES, 0);

	if (vc->pcr)

		mtspr(SPRN_PCR, PCR_MASK);