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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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13
arch/powerpc/kvm/book3s_hv.c
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@@ -2111,6 +2111,15 @@ 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(1, "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 +2154,12 @@ 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)