POWER9 CPUs have independent MMU contexts per thread, so KVM does not
need to quiesce secondary threads, so the hwthread_req/hwthread_state
protocol does not have to be used. So patch it away on POWER9, and patch
away the branch from the Linux idle wakeup to kvm_start_guest that is
never used.
Add a warning and error out of kvmppc_grab_hwthread in case it is ever
called on POWER9.
This avoids a hwsync in the idle wakeup path on POWER9.
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
arch/powerpc/include/asm/kvm_book3s_asm.h | 4 ++++
arch/powerpc/kernel/idle_book3s.S | 30 +++++++++++++++---------------
arch/powerpc/kvm/book3s_hv.c | 14 +++++++++++++-
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 8 ++++++++
4 files changed, 40 insertions(+), 16 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
index 7cea76f11c26..83596f32f50b 100644
--- a/arch/powerpc/include/asm/kvm_book3s_asm.h
+++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
@@ -104,6 +104,10 @@ struct kvmppc_host_state {
u8 napping;
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+ /*
+ * hwthread_req/hwthread_state pair is used to pull sibling threads
+ * out of guest on pre-ISAv3.0B CPUs where threads share MMU.
+ */
u8 hwthread_req;
u8 hwthread_state;
u8 host_ipi;
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index e6252c5a57a4..9a9a28f0758d 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -243,12 +243,6 @@ enter_winkle:
* r3 - PSSCR value corresponding to the requested stop state.
*/
power_enter_stop:
-#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
- /* Tell KVM we're entering idle */
- li r4,KVM_HWTHREAD_IN_IDLE
- /* DO THIS IN REAL MODE! See comment above. */
- stb r4,HSTATE_HWTHREAD_STATE(r13)
-#endif
/*
* Check if we are executing the lite variant with ESL=EC=0
*/
@@ -411,6 +405,18 @@ pnv_powersave_wakeup_mce:
b pnv_powersave_wakeup
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+kvm_start_guest_check:
+ li r0,KVM_HWTHREAD_IN_KERNEL
+ stb r0,HSTATE_HWTHREAD_STATE(r13)
+ /* Order setting hwthread_state vs. testing hwthread_req */
+ sync
+ lbz r0,HSTATE_HWTHREAD_REQ(r13)
+ cmpwi r0,0
+ beqlr
+ b kvm_start_guest
+#endif
+
/*
* Called from reset vector for powersave wakeups.
* cr3 - set to gt if waking up with partial/complete hypervisor state loss
@@ -435,15 +441,9 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
mr r3,r12
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
- li r0,KVM_HWTHREAD_IN_KERNEL
- stb r0,HSTATE_HWTHREAD_STATE(r13)
- /* Order setting hwthread_state vs. testing hwthread_req */
- sync
- lbz r0,HSTATE_HWTHREAD_REQ(r13)
- cmpwi r0,0
- beq 1f
- b kvm_start_guest
-1:
+BEGIN_FTR_SECTION
+ bl kvm_start_guest_check
+END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
#endif
/* Return SRR1 from power7_nap() */
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 359c79cdf0cc..e34cd6fb947b 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2111,6 +2111,16 @@ static int kvmppc_grab_hwthread(int cpu)
struct paca_struct *tpaca;
long timeout = 10000;
+ /*
+ * ISA v3.0 idle routines do not set hwthread_state or test
+ * hwthread_req, so they can not grab idle threads.
+ */
+ if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+ WARN_ON(1);
+ pr_err("KVM: can not control sibling threads\n");
+ return -EBUSY;
+ }
+
tpaca = &paca[cpu];
/* Ensure the thread won't go into the kernel if it wakes */
@@ -2145,10 +2155,12 @@ static void kvmppc_release_hwthread(int cpu)
struct paca_struct *tpaca;
tpaca = &paca[cpu];
- tpaca->kvm_hstate.hwthread_req = 0;
tpaca->kvm_hstate.kvm_vcpu = NULL;
tpaca->kvm_hstate.kvm_vcore = NULL;
tpaca->kvm_hstate.kvm_split_mode = NULL;
+ if (!cpu_has_feature(CPU_FTR_ARCH_300))
+ tpaca->kvm_hstate.hwthread_req = 0;
+
}
static void radix_flush_cpu(struct kvm *kvm, int cpu, struct kvm_vcpu *vcpu)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index c52184a8efdf..3e024fd71fe8 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -149,9 +149,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
subf r4, r4, r3
mtspr SPRN_DEC, r4
+BEGIN_FTR_SECTION
/* hwthread_req may have got set by cede or no vcpu, so clear it */
li r0, 0
stb r0, HSTATE_HWTHREAD_REQ(r13)
+END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
/*
* For external interrupts we need to call the Linux
@@ -314,6 +316,7 @@ kvm_novcpu_exit:
* Relocation is off and most register values are lost.
* r13 points to the PACA.
* r3 contains the SRR1 wakeup value, SRR1 is trashed.
+ * This is not used by ISAv3.0B processors.
*/
.globl kvm_start_guest
kvm_start_guest:
@@ -432,6 +435,9 @@ kvm_secondary_got_guest:
* While waiting we also need to check if we get given a vcpu to run.
*/
kvm_no_guest:
+BEGIN_FTR_SECTION
+ twi 31,0,0
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
lbz r3, HSTATE_HWTHREAD_REQ(r13)
cmpwi r3, 0
bne 53f
@@ -2509,8 +2515,10 @@ kvm_do_nap:
clrrdi r0, r0, 1
mtspr SPRN_CTRLT, r0
+BEGIN_FTR_SECTION
li r0,1
stb r0,HSTATE_HWTHREAD_REQ(r13)
+END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
mfspr r5,SPRN_LPCR
ori r5,r5,LPCR_PECE0 | LPCR_PECE1
BEGIN_FTR_SECTION
--
2.13.3
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