Commit 7d0a5e62 authored by Janosch Frank's avatar Janosch Frank Committed by Christian Borntraeger

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: default avatarJanosch Frank <frankja@linux.vnet.ibm.com>
Acked-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 95ca2cb5
...@@ -652,6 +652,7 @@ struct kvm_arch{ ...@@ -652,6 +652,7 @@ struct kvm_arch{
wait_queue_head_t ipte_wq; wait_queue_head_t ipte_wq;
int ipte_lock_count; int ipte_lock_count;
struct mutex ipte_mutex; struct mutex ipte_mutex;
struct ratelimit_state sthyi_limit;
spinlock_t start_stop_lock; spinlock_t start_stop_lock;
struct sie_page2 *sie_page2; struct sie_page2 *sie_page2;
struct kvm_s390_cpu_model model; struct kvm_s390_cpu_model model;
......
...@@ -1151,6 +1151,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) ...@@ -1151,6 +1151,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
rc = -ENOMEM; rc = -ENOMEM;
ratelimit_state_init(&kvm->arch.sthyi_limit, 5 * HZ, 500);
kvm->arch.use_esca = 0; /* start with basic SCA */ kvm->arch.use_esca = 0; /* start with basic SCA */
rwlock_init(&kvm->arch.sca_lock); rwlock_init(&kvm->arch.sca_lock);
kvm->arch.sca = (struct bsca_block *) get_zeroed_page(GFP_KERNEL); kvm->arch.sca = (struct bsca_block *) get_zeroed_page(GFP_KERNEL);
......
...@@ -12,6 +12,7 @@ ...@@ -12,6 +12,7 @@
#include <linux/errno.h> #include <linux/errno.h>
#include <linux/pagemap.h> #include <linux/pagemap.h>
#include <linux/vmalloc.h> #include <linux/vmalloc.h>
#include <linux/ratelimit.h>
#include <asm/kvm_host.h> #include <asm/kvm_host.h>
#include <asm/asm-offsets.h> #include <asm/asm-offsets.h>
...@@ -403,6 +404,16 @@ int handle_sthyi(struct kvm_vcpu *vcpu) ...@@ -403,6 +404,16 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
u64 code, addr, cc = 0; u64 code, addr, cc = 0;
struct sthyi_sctns *sctns = NULL; 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, &reg1, &reg2); kvm_s390_get_regs_rre(vcpu, &reg1, &reg2);
code = vcpu->run->s.regs.gprs[reg1]; code = vcpu->run->s.regs.gprs[reg1];
addr = vcpu->run->s.regs.gprs[reg2]; addr = vcpu->run->s.regs.gprs[reg2];
......
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