[RFC PATCH 35/43] KVM: PPC: Book3S HV P9: Demand fault TM facility registers
Nicholas Piggin
npiggin at gmail.com
Tue Jun 22 20:57:28 AEST 2021
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.
-304 cycles (6681) POWER9 virt-mode NULL hcall with the previous patch
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
arch/powerpc/include/asm/kvm_host.h | 1 +
arch/powerpc/kvm/book3s_hv.c | 21 +++++++++++++++++----
arch/powerpc/kvm/book3s_hv_nested.c | 2 +-
arch/powerpc/kvm/book3s_hv_p9_entry.c | 18 ++++++++++++------
4 files changed, 31 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index bee95106c1f2..d79f0b1b1578 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -586,6 +586,7 @@ struct kvm_vcpu_arch {
ulong ppr;
u32 pspb;
u8 load_ebb;
+ u8 load_tm;
ulong fscr;
ulong shadow_fscr;
ulong ebbhr;
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 99e9da078e7d..2430725f29f7 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1373,6 +1373,13 @@ static int kvmppc_ebb_unavailable(struct kvm_vcpu *vcpu)
return RESUME_GUEST;
}
+static int kvmppc_tm_unavailable(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.hfscr |= HFSCR_TM;
+
+ return RESUME_GUEST;
+}
+
static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu,
struct task_struct *tsk)
{
@@ -1654,6 +1661,8 @@ XXX benchmark guest exits
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);
@@ -1775,6 +1784,8 @@ static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu)
r = kvmppc_pmu_unavailable(vcpu);
if (cause == FSCR_EBB_LG && (vcpu->arch.nested_hfscr & HFSCR_EBB))
r = kvmppc_ebb_unavailable(vcpu);
+ if (cause == FSCR_TM_LG && (vcpu->arch.nested_hfscr & HFSCR_TM))
+ r = kvmppc_tm_unavailable(vcpu);
if (r == EMULATE_FAIL)
r = RESUME_HOST;
@@ -3737,8 +3748,9 @@ 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);
@@ -4453,8 +4465,9 @@ 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);
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index ee8668f056f9..5a534f7924f2 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -168,7 +168,7 @@ static void sanitise_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
* but preserve the interrupt cause field and facilities that might
* be disabled for demand faulting in the L1.
*/
- hr->hfscr &= (HFSCR_INTR_CAUSE | HFSCR_PM | HFSCR_EBB |
+ hr->hfscr &= (HFSCR_INTR_CAUSE | HFSCR_PM | HFSCR_TM | HFSCR_EBB |
vcpu->arch.hfscr);
/* Don't let data address watchpoint match in hypervisor state */
diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c
index cf41261daa97..653f2765a399 100644
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
@@ -284,8 +284,9 @@ static void store_spr_state(struct kvm_vcpu *vcpu)
void load_vcpu_state(struct kvm_vcpu *vcpu,
struct p9_host_os_sprs *host_os_sprs)
{
- 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)) {
unsigned long msr = vcpu->arch.shregs.msr;
if (MSR_TM_ACTIVE(msr)) {
kvmppc_restore_tm_hv(vcpu, msr, true);
@@ -316,8 +317,9 @@ void store_vcpu_state(struct kvm_vcpu *vcpu)
#endif
vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
- 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)) {
unsigned long msr = vcpu->arch.shregs.msr;
if (MSR_TM_ACTIVE(msr)) {
kvmppc_save_tm_hv(vcpu, msr, true);
@@ -326,6 +328,9 @@ void store_vcpu_state(struct kvm_vcpu *vcpu)
vcpu->arch.tfhar = mfspr(SPRN_TFHAR);
vcpu->arch.tfiar = mfspr(SPRN_TFIAR);
}
+ vcpu->arch.load_tm++; /* see load_ebb comment for details */
+ if (!vcpu->arch.load_tm)
+ vcpu->arch.hfscr &= ~HFSCR_TM;
}
}
EXPORT_SYMBOL_GPL(store_vcpu_state);
@@ -615,8 +620,9 @@ 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. */
--
2.23.0
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