Re: [PATCH v5 03/12] KVM/x86: KVM_CAP_X86_GUEST_LBR

[Andi Kleen]

> + case KVM_CAP_X86_GUEST_LBR:
> + r = -EINVAL;
> + if (cap->args[0] &&
> + x86_perf_get_lbr_stack(>arch.lbr_stack)) {
> + pr_err("Failed to enable the guest lbr feature\n");

Remove the pr_err. We don't want unprivileged users trigger unlimited
kernel printk.

[PATCH v5 03/12] KVM/x86: KVM_CAP_X86_GUEST_LBR

[Wei Wang]

Introduce KVM_CAP_X86_GUEST_LBR to allow per-VM enabling of the guest
lbr feature.

Signed-off-by: Wei Wang 
Cc: Paolo Bonzini 
Cc: Andi Kleen 
Cc: Peter Zijlstra 
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/x86.c  | 15 +++
 include/uapi/linux/kvm.h|  1 +
 3 files changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4660ce9..e6f6760 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -869,6 +869,7 @@ struct kvm_arch {
atomic_t vapics_in_nmi_mode;
struct mutex apic_map_lock;
struct kvm_apic_map *apic_map;
+   struct x86_perf_lbr_stack lbr_stack;
 
bool apic_access_page_done;
 
@@ -877,6 +878,7 @@ struct kvm_arch {
bool mwait_in_guest;
bool hlt_in_guest;
bool pause_in_guest;
+   bool lbr_in_guest;
 
unsigned long irq_sources_bitmap;
s64 kvmclock_offset;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3d27206..2cdebe7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3028,6 +3028,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long 
ext)
case KVM_CAP_GET_MSR_FEATURES:
case KVM_CAP_MSR_PLATFORM_INFO:
case KVM_CAP_EXCEPTION_PAYLOAD:
+   case KVM_CAP_X86_GUEST_LBR:
r = 1;
break;
case KVM_CAP_SYNC_REGS:
@@ -4562,6 +4563,20 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
kvm->arch.exception_payload_enabled = cap->args[0];
r = 0;
break;
+   case KVM_CAP_X86_GUEST_LBR:
+   r = -EINVAL;
+   if (cap->args[0] &&
+   x86_perf_get_lbr_stack(>arch.lbr_stack)) {
+   pr_err("Failed to enable the guest lbr feature\n");
+   break;
+   }
+   if (copy_to_user((void __user *)cap->args[1],
+>arch.lbr_stack,
+sizeof(struct x86_perf_lbr_stack)))
+   break;
+   kvm->arch.lbr_in_guest = cap->args[0];
+   r = 0;
+   break;
default:
r = -EINVAL;
break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6d4ea4b..a7cac96 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -988,6 +988,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_ARM_VM_IPA_SIZE 165
 #define KVM_CAP_MANUAL_DIRTY_LOG_PROTECT 166
 #define KVM_CAP_HYPERV_CPUID 167
+#define KVM_CAP_X86_GUEST_LBR 168
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.7.4