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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: 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/20211123095231.1036501-38-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-11-23 19:52:15 +10:00 committed by Michael Ellerman
parent a3e18ca8ab
commit 022ecb960c
3 changed files with 34 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/powerpc/include/asm/kvm_host.h
View File

@ -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;

26
arch/powerpc/kvm/book3s_hv.c
View File

@ -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);

15
arch/powerpc/kvm/book3s_hv_p9_entry.c
View File

@ -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. */