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| author | Heiko Carstens <hca@linux.ibm.com> | 2024-11-26 11:25:14 +0100 |
|---|---|---|
| committer | Heiko Carstens <hca@linux.ibm.com> | 2024-11-27 12:55:15 +0100 |
| commit | 7061c63919bde3bb0daa63e700a117ab1f2c97b1 (patch) | |
| tree | 67cb3145fd6e76903b4f940bbdd09af073fb1054 /arch/s390 | |
| parent | 5618c53d96d1bf2df07df8b9204773db28acbc1b (diff) | |
| download | linux-stable-7061c63919bde3bb0daa63e700a117ab1f2c97b1.tar.gz linux-stable-7061c63919bde3bb0daa63e700a117ab1f2c97b1.tar.bz2 linux-stable-7061c63919bde3bb0daa63e700a117ab1f2c97b1.zip | |
KVM: s390: Remove one byte cmpxchg() usage
Within sca_clear_ext_call() cmpxchg() is used to clear one or two bytes
(depending on sca format). The cmpxchg() calls are not supposed to fail; if
so that would be a bug. Given that cmpxchg() usage on one and two byte
areas generates very inefficient code, replace them with block concurrent
WRITE_ONCE() calls, and remove the WARN_ON().
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20241126102515.3178914-3-hca@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'arch/s390')
| -rw-r--r-- | arch/s390/kvm/interrupt.c | 13 |
1 files changed, 2 insertions, 11 deletions
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index eff69018cbeb..ea8dce299954 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -118,8 +118,6 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) static void sca_clear_ext_call(struct kvm_vcpu *vcpu) { - int rc, expect; - if (!kvm_s390_use_sca_entries()) return; kvm_s390_clear_cpuflags(vcpu, CPUSTAT_ECALL_PEND); @@ -128,23 +126,16 @@ static void sca_clear_ext_call(struct kvm_vcpu *vcpu) struct esca_block *sca = vcpu->kvm->arch.sca; union esca_sigp_ctrl *sigp_ctrl = &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union esca_sigp_ctrl old; - old = READ_ONCE(*sigp_ctrl); - expect = old.value; - rc = cmpxchg(&sigp_ctrl->value, old.value, 0); + WRITE_ONCE(sigp_ctrl->value, 0); } else { struct bsca_block *sca = vcpu->kvm->arch.sca; union bsca_sigp_ctrl *sigp_ctrl = &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union bsca_sigp_ctrl old; - old = READ_ONCE(*sigp_ctrl); - expect = old.value; - rc = cmpxchg(&sigp_ctrl->value, old.value, 0); + WRITE_ONCE(sigp_ctrl->value, 0); } read_unlock(&vcpu->kvm->arch.sca_lock); - WARN_ON(rc != expect); /* cannot clear? */ } int psw_extint_disabled(struct kvm_vcpu *vcpu) |