From 7d0a5e62411a9223512c6af2e4c08a2d7c00fa2e Mon Sep 17 00:00:00 2001 From: Janosch Frank Date: Tue, 10 May 2016 15:03:42 +0200 Subject: [PATCH] KVM: s390: Limit sthyi execution Store hypervisor information is a valid instruction not only in supervisor state but also in problem state, i.e. the guest's userspace. Its execution is not only computational and memory intensive, but also has to get hold of the ipte lock to write to the guest's memory. This lock is not intended to be held often and long, especially not from the untrusted guest userspace. Therefore we apply rate limiting of sthyi executions per VM. Signed-off-by: Janosch Frank Acked-by: David Hildenbrand Signed-off-by: Christian Borntraeger --- arch/s390/include/asm/kvm_host.h | 1 + arch/s390/kvm/kvm-s390.c | 2 ++ arch/s390/kvm/sthyi.c | 11 +++++++++++ 3 files changed, 14 insertions(+) diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index 7233b1c..bcc20dc 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -652,6 +652,7 @@ struct kvm_arch{ wait_queue_head_t ipte_wq; int ipte_lock_count; struct mutex ipte_mutex; + struct ratelimit_state sthyi_limit; spinlock_t start_stop_lock; struct sie_page2 *sie_page2; struct kvm_s390_cpu_model model; diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 1c10254..44297ff 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1151,6 +1151,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) rc = -ENOMEM; + ratelimit_state_init(&kvm->arch.sthyi_limit, 5 * HZ, 500); + kvm->arch.use_esca = 0; /* start with basic SCA */ rwlock_init(&kvm->arch.sca_lock); kvm->arch.sca = (struct bsca_block *) get_zeroed_page(GFP_KERNEL); diff --git a/arch/s390/kvm/sthyi.c b/arch/s390/kvm/sthyi.c index 894d562..bd98b7d 100644 --- a/arch/s390/kvm/sthyi.c +++ b/arch/s390/kvm/sthyi.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include @@ -403,6 +404,16 @@ int handle_sthyi(struct kvm_vcpu *vcpu) u64 code, addr, cc = 0; struct sthyi_sctns *sctns = NULL; + /* + * STHYI requires extensive locking in the higher hypervisors + * and is very computational/memory expensive. Therefore we + * ratelimit the executions per VM. + */ + if (!__ratelimit(&vcpu->kvm->arch.sthyi_limit)) { + kvm_s390_retry_instr(vcpu); + return 0; + } + kvm_s390_get_regs_rre(vcpu, ®1, ®2); code = vcpu->run->s.regs.gprs[reg1]; addr = vcpu->run->s.regs.gprs[reg2]; -- 2.7.4