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KVM: PPC: Book3S HV: POWER9 does not require secondary thread management

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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@gmail.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
[mpe: Use WARN(...) instead of WARN_ON()/pr_err(...)]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2017-08-25 14:30:33 +10:00
committed by Michael Ellerman
parent 94171b19c3
commit 94a04bc25a
4 changed files with 48 additions and 12 deletions
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35
arch/powerpc/kernel/idle_book3s.S
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@@ -242,13 +242,20 @@ 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 */
power_enter_stop_kvm_rm:
/*
* This is currently unused because POWER9 KVM does not have to
* gather secondary threads into sibling mode, but the code is
* here in case that function is required.
*
* 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
power_enter_stop:
/*
* Check if we are executing the lite variant with ESL=EC=0
*/
@@ -411,6 +418,18 @@ 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 +454,9 @@ 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() */