[PULL 01/36] powerpc: kvm: optimize "sc 1" as fast return

Alexander Graf
2014-01-29T16:13:20Z

From: Liu Ping Fan <kernelfans@gmail.com>

In some scene, e.g openstack CI, PR guest can trigger "sc 1" frequently,
this patch optimizes the path by directly delivering BOOK3S_INTERRUPT_SYSCALL
to HV guest, so powernv can return to HV guest without heavy exit, i.e,
no need to swap TLB, HTAB,.. etc

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/kvm/book3s_hv.c | 10 ++++------
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 19 ++++++++++++++++++-
2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 072287f..93203bb 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -669,12 +669,10 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
/* hcall - punt to userspace */
int i;

- if (vcpu->arch.shregs.msr & MSR_PR) {
- /* sc 1 from userspace - reflect to guest syscall */
- kvmppc_book3s_queue_irqprio(vcpu, BOOK3S_INTERRUPT_SYSCALL);
- r = RESUME_GUEST;
- break;
- }
+ /* hypercall with MSR_PR has already been handled in rmode,
+ * and never reaches here.
+ */
+
run->papr_hcall.nr = kvmppc_get_gpr(vcpu, 3);
for (i = 0; i < 9; ++i)
run->papr_hcall.args[i] = kvmppc_get_gpr(vcpu, 4 + i);
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index bc8de75..d5ddc2d 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -686,6 +686,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
5: mtspr SPRN_SRR0, r6
mtspr SPRN_SRR1, r7

+/*
+ * Required state:
+ * R4 = vcpu
+ * R10: value for HSRR0
+ * R11: value for HSRR1
+ * R13 = PACA
+ */
fast_guest_return:
li r0,0
stb r0,VCPU_CEDED(r4) /* cancel cede */
@@ -1471,7 +1478,8 @@ kvmppc_hisi:
hcall_try_real_mode:
ld r3,VCPU_GPR(R3)(r9)
andi. r0,r11,MSR_PR
- bne guest_exit_cont
+ /* sc 1 from userspace - reflect to guest syscall */
+ bne sc_1_fast_return
clrrdi r3,r3,2
cmpldi r3,hcall_real_table_end - hcall_real_table
bge guest_exit_cont
@@ -1492,6 +1500,15 @@ hcall_try_real_mode:
ld r11,VCPU_MSR(r4)
b fast_guest_return

+sc_1_fast_return:
+ mtspr SPRN_SRR0,r10
+ mtspr SPRN_SRR1,r11
+ li r10, BOOK3S_INTERRUPT_SYSCALL
+ li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
+ rotldi r11, r11, 63
+ mr r4,r9
+ b fast_guest_return
+
/* We've attempted a real mode hcall, but it's punted it back
* to userspace. We need to restore some clobbered volatiles
* before resuming the pass-it-to-qemu path */
--
1.8.1.4