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| author | Nicholas Piggin <npiggin@gmail.com> | 2021-11-23 19:51:44 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-11-24 21:08:57 +1100 |
| commit | 34bf08a2079fffc7206a1ae93086ab8167e0afb6 (patch) | |
| tree | 4317b21407fa968de30134a48317748a86d45d69 | |
| parent | 9581991a60817abe311c2581ae4554b28bfa32f1 (diff) | |
| download | linux-34bf08a2079fffc7206a1ae93086ab8167e0afb6.tar.gz | |
KVM: PPC: Book3S HV P9: Reduce mftb per guest entry/exit
mftb is serialising (dispatch next-to-complete) so it is heavy weight
for a mfspr. Avoid reading it multiple times in the entry or exit paths.
A small number of cycles delay to timers is tolerable.
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/20211123095231.1036501-7-npiggin@gmail.com
| -rw-r--r-- | arch/powerpc/kvm/book3s_hv.c | 4 | ||||
| -rw-r--r-- | arch/powerpc/kvm/book3s_hv_p9_entry.c | 5 |
2 files changed, 5 insertions, 4 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 3322edbafc64..5fc0c168a39a 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3940,7 +3940,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, * * XXX: Another day's problem. */ - mtspr(SPRN_DEC, vcpu->arch.dec_expires - mftb()); + mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb); if (kvmhv_on_pseries()) { /* @@ -4063,7 +4063,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, vc->in_guest = 0; next_timer = timer_get_next_tb(); - set_dec(next_timer - mftb()); + set_dec(next_timer - tb); /* We may have raced with new irq work */ if (test_irq_work_pending()) set_dec(1); diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c index 0ff9ddb5e7ca..bd8cf0a65ce8 100644 --- a/arch/powerpc/kvm/book3s_hv_p9_entry.c +++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c @@ -203,7 +203,8 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc unsigned long host_dawr1; unsigned long host_dawrx1; - hdec = time_limit - mftb(); + tb = mftb(); + hdec = time_limit - tb; if (hdec < 0) return BOOK3S_INTERRUPT_HV_DECREMENTER; @@ -215,7 +216,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc vcpu->arch.ceded = 0; if (vc->tb_offset) { - u64 new_tb = mftb() + vc->tb_offset; + u64 new_tb = tb + vc->tb_offset; mtspr(SPRN_TBU40, new_tb); tb = mftb(); if ((tb & 0xffffff) < (new_tb & 0xffffff)) |