Commit 022ecb96 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

KVM: PPC: Book3S HV P9: Demand fault TM facility registers 



Use HFSCR facility disabling to implement demand faulting for TM, with
a hysteresis counter similar to the load_fp etc counters in context
switching that implement the equivalent demand faulting for userspace
facilities.

This speeds up guest entry/exit by avoiding the register save/restore
when a guest is not frequently using them. When a guest does use them
often, there will be some additional demand fault overhead, but these
are not commonly used facilities.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Reviewed-by: default avatarFabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-38-npiggin@gmail.com
parent a3e18ca8

arch/powerpc/include/asm/kvm_host.h

+3 −0
Original line number Diff line number Diff line
@@ -580,6 +580,9 @@ struct kvm_vcpu_arch { 
	ulong ppr;

	u32 pspb;

	u8 load_ebb;

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM

	u8 load_tm;

#endif

	ulong fscr;

	ulong shadow_fscr;

	ulong ebbhr;

arch/powerpc/kvm/book3s_hv.c

+20 −6
Original line number Diff line number Diff line
@@ -1446,6 +1446,16 @@ static int kvmppc_ebb_unavailable(struct kvm_vcpu *vcpu) 
	return RESUME_GUEST;

}



static int kvmppc_tm_unavailable(struct kvm_vcpu *vcpu)

{

	if (!(vcpu->arch.hfscr_permitted & HFSCR_TM))

		return EMULATE_FAIL;



	vcpu->arch.hfscr |= HFSCR_TM;



	return RESUME_GUEST;

}



static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu,

				 struct task_struct *tsk)

{
@@ -1739,6 +1749,8 @@ static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu, 
				r = kvmppc_pmu_unavailable(vcpu);

			if (cause == FSCR_EBB_LG)

				r = kvmppc_ebb_unavailable(vcpu);

			if (cause == FSCR_TM_LG)

				r = kvmppc_tm_unavailable(vcpu);

		}

		if (r == EMULATE_FAIL) {

			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
@@ -2783,9 +2795,9 @@ static int kvmppc_core_vcpu_create_hv(struct kvm_vcpu *vcpu) 
	vcpu->arch.hfscr_permitted = vcpu->arch.hfscr;



	/*

	 * PM, EBB is demand-faulted so start with it clear.

	 * PM, EBB, TM are demand-faulted so start with it clear.

	 */

	vcpu->arch.hfscr &= ~(HFSCR_PM | HFSCR_EBB);

	vcpu->arch.hfscr &= ~(HFSCR_PM | HFSCR_EBB | HFSCR_TM);



	kvmppc_mmu_book3s_hv_init(vcpu);
@@ -3868,8 +3880,9 @@ static int kvmhv_vcpu_entry_p9_nested(struct kvm_vcpu *vcpu, u64 time_limit, uns 
		msr |= MSR_VEC;

	if (cpu_has_feature(CPU_FTR_VSX))

		msr |= MSR_VSX;

	if (cpu_has_feature(CPU_FTR_TM) ||

	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))

	if ((cpu_has_feature(CPU_FTR_TM) ||

	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) &&

			(vcpu->arch.hfscr & HFSCR_TM))

		msr |= MSR_TM;

	msr = msr_check_and_set(msr);
@@ -4608,8 +4621,9 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) 
		msr |= MSR_VEC;

	if (cpu_has_feature(CPU_FTR_VSX))

		msr |= MSR_VSX;

	if (cpu_has_feature(CPU_FTR_TM) ||

	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))

	if ((cpu_has_feature(CPU_FTR_TM) ||

	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) &&

			(vcpu->arch.hfscr & HFSCR_TM))

		msr |= MSR_TM;

	msr = msr_check_and_set(msr);

arch/powerpc/kvm/book3s_hv_p9_entry.c

+11 −4
Original line number Diff line number Diff line
@@ -310,7 +310,7 @@ bool load_vcpu_state(struct kvm_vcpu *vcpu, 
		if (MSR_TM_ACTIVE(guest_msr)) {

			kvmppc_restore_tm_hv(vcpu, guest_msr, true);

			ret = true;

		} else {

		} else if (vcpu->arch.hfscr & HFSCR_TM) {

			mtspr(SPRN_TEXASR, vcpu->arch.texasr);

			mtspr(SPRN_TFHAR, vcpu->arch.tfhar);

			mtspr(SPRN_TFIAR, vcpu->arch.tfiar);
@@ -346,10 +346,16 @@ void store_vcpu_state(struct kvm_vcpu *vcpu) 
		unsigned long guest_msr = vcpu->arch.shregs.msr;

		if (MSR_TM_ACTIVE(guest_msr)) {

			kvmppc_save_tm_hv(vcpu, guest_msr, true);

		} else {

		} else if (vcpu->arch.hfscr & HFSCR_TM) {

			vcpu->arch.texasr = mfspr(SPRN_TEXASR);

			vcpu->arch.tfhar = mfspr(SPRN_TFHAR);

			vcpu->arch.tfiar = mfspr(SPRN_TFIAR);



			if (!vcpu->arch.nested) {

				vcpu->arch.load_tm++; /* see load_ebb comment */

				if (!vcpu->arch.load_tm)

					vcpu->arch.hfscr &= ~HFSCR_TM;

			}

		}

	}

#endif
@@ -641,8 +647,9 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
		msr |= MSR_VEC;

	if (cpu_has_feature(CPU_FTR_VSX))

		msr |= MSR_VSX;

	if (cpu_has_feature(CPU_FTR_TM) ||

	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))

	if ((cpu_has_feature(CPU_FTR_TM) ||

	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) &&

			(vcpu->arch.hfscr & HFSCR_TM))

		msr |= MSR_TM;

	msr = msr_check_and_set(msr);

	/* Save MSR for restore. This is after hard disable, so EE is clear. */