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KVM: svm: add nrips module parameter 

Allow testing code for old processors that lack the next RIP save
feature, by disabling usage of the next_rip field.

Nested hypervisors however get the feature unconditionally.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2019-06-20 14:13:33 +02:00
parent c550505b57
commit d647eb63e6
1 changed files with 12 additions and 3 deletions
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15
arch/x86/kvm/svm.c
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@ -367,6 +367,10 @@ static int avic;
module_param(avic, int, S_IRUGO);
#endif
/* enable/disable Next RIP Save */
static int nrips = true;
module_param(nrips, int, 0444);
/* enable/disable Virtual VMLOAD VMSAVE */
static int vls = true;
module_param(vls, int, 0444);
@ -773,7 +777,7 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
if (svm->vmcb->control.next_rip != 0) {
if (nrips && svm->vmcb->control.next_rip != 0) {
WARN_ON_ONCE(!static_cpu_has(X86_FEATURE_NRIPS));
svm->next_rip = svm->vmcb->control.next_rip;
}
@ -810,7 +814,7 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu)
kvm_deliver_exception_payload(&svm->vcpu);
if (nr == BP_VECTOR && !static_cpu_has(X86_FEATURE_NRIPS)) {
if (nr == BP_VECTOR && !nrips) {
unsigned long rip, old_rip = kvm_rip_read(&svm->vcpu);
/*
@ -1367,6 +1371,11 @@ static __init int svm_hardware_setup(void)
} else
kvm_disable_tdp();
if (nrips) {
if (!boot_cpu_has(X86_FEATURE_NRIPS))
nrips = false;
}
if (avic) {
if (!npt_enabled ||
!boot_cpu_has(X86_FEATURE_AVIC) ||
@ -3938,7 +3947,7 @@ static int rdpmc_interception(struct vcpu_svm *svm)
{
int err;
if (!static_cpu_has(X86_FEATURE_NRIPS))
if (!nrips)
return emulate_on_interception(svm);
err = kvm_rdpmc(&svm->vcpu);