KVM: x86/pmu: Gate all "unimplemented MSR" prints on report_ignored_msrs

Add helpers to print unimplemented MSR accesses and condition all such
prints on report_ignored_msrs, i.e. honor userspace's request to not
print unimplemented MSRs.  Even though vcpu_unimpl() is ratelimited,
printing can still be problematic, e.g. if a print gets stalled when host
userspace is writing MSRs during live migration, an effective stall can
result in very noticeable disruption in the guest.

E.g. the profile below was taken while calling KVM_SET_MSRS on the PMU
counters while the PMU was disabled in KVM.

  -   99.75%     0.00%  [.] __ioctl
   - __ioctl
      - 99.74% entry_SYSCALL_64_after_hwframe
           do_syscall_64
           sys_ioctl
         - do_vfs_ioctl
            - 92.48% kvm_vcpu_ioctl
               - kvm_arch_vcpu_ioctl
                  - 85.12% kvm_set_msr_ignored_check
                       svm_set_msr
                       kvm_set_msr_common
                       printk
                       vprintk_func
                       vprintk_default
                       vprintk_emit
                       console_unlock
                       call_console_drivers
                       univ8250_console_write
                       serial8250_console_write
                       uart_console_write

Reported-by: Aaron Lewis <aaronlewis@google.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20230124234905.3774678-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 4 insertions, 6 deletions

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 71aff0edc0ed..3eb8caf87ee4 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1430,8 +1430,7 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
 		return syndbg_set_msr(vcpu, msr, data, host);
 	default:
-		vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n",
-			    msr, data);
+		kvm_pr_unimpl_wrmsr(vcpu, msr, data);
 		return 1;
 	}
 	return 0;
@@ -1552,8 +1551,7 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 			return 1;
 		break;
 	default:
-		vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n",
-			    msr, data);
+		kvm_pr_unimpl_wrmsr(vcpu, msr, data);
 		return 1;
 	}
 
@@ -1608,7 +1606,7 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
 		return syndbg_get_msr(vcpu, msr, pdata, host);
 	default:
-		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
+		kvm_pr_unimpl_rdmsr(vcpu, msr);
 		return 1;
 	}
 
@@ -1673,7 +1671,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 		data = APIC_BUS_FREQUENCY;
 		break;
 	default:
-		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
+		kvm_pr_unimpl_rdmsr(vcpu, msr);
 		return 1;
 	}
 	*pdata = data;