[PATCH] KVM: s390: log machine checks more aggressively

[PATCH] KVM: s390: log machine checks more aggressively

[Christian Borntraeger]

KVM will reinject machine checks that happen during guest activity.
From a host perspective this machine check is no longer visible
and even for the guest, the guest might decide to only kill a
userspace program or even ignore the machine check.
As this can be a disruptive event nevertheless, we should log this
not only in the VM debug event (that gets lost after guest shutdown)
but also on the global KVM event as well as syslog.
Consolidate the logging and log with loglevel 2 and higher.

Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
---

 arch/s390/kvm/interrupt.c | 6 ++++++
 arch/s390/kvm/kvm-s390.c  | 1 -
 arch/s390/kvm/vsie.c      | 1 -
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 18932a65ca68..9885d4bcb6ae 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -2824,6 +2824,12 @@ void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 	int rc;
 
 	mci.val = mcck_info->mcic;
+
+	/* log machine checks being reinjected on all debugs */
+	VCPU_EVENT(vcpu, 2, "guest machine check %lx", mci.val);
+	KVM_EVENT(2, "guest_machine check %lx", mci.val);
+	pr_info("guest_machine check pid %d: %lx", current->pid, mci.val);
+
 	if (mci.sr)
 		cr14 |= CR14_RECOVERY_SUBMASK;
 	if (mci.dg)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index bc7d6fa66eaf..1668580008c6 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4634,7 +4634,6 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
 	vcpu->run->s.regs.gprs[15] = vcpu->arch.sie_block->gg15;
 
 	if (exit_reason == -EINTR) {
-		VCPU_EVENT(vcpu, 3, "%s", "machine check");
 		sie_page = container_of(vcpu->arch.sie_block,
 					struct sie_page, sie_block);
 		mcck_info = &sie_page->mcck_info;
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index d249b10044eb..c0d36afd4023 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -1179,7 +1179,6 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page, struc
 	kvm_vcpu_srcu_read_lock(vcpu);
 
 	if (rc == -EINTR) {
-		VCPU_EVENT(vcpu, 3, "%s", "machine check");
 		kvm_s390_reinject_machine_check(vcpu, &vsie_page->mcck_info);
 		return 0;
 	}
-- 
2.53.0

Re: [PATCH] KVM: s390: log machine checks more aggressively

[Janosch Frank]

On 3/9/26 12:59, Christian Borntraeger wrote:
> KVM will reinject machine checks that happen during guest activity.
>  From a host perspective this machine check is no longer visible
> and even for the guest, the guest might decide to only kill a
> userspace program or even ignore the machine check.
> As this can be a disruptive event nevertheless, we should log this
> not only in the VM debug event (that gets lost after guest shutdown)
> but also on the global KVM event as well as syslog.
> Consolidate the logging and log with loglevel 2 and higher.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>

Acked-by: Janosch Frank <frankja@linux.ibm.com>

Re: [PATCH] KVM: s390: log machine checks more aggressively

[Hendrik Brueckner]

On Mon, Mar 09, 2026 at 12:59:04PM +0100, Christian Borntraeger wrote:
> KVM will reinject machine checks that happen during guest activity.
> From a host perspective this machine check is no longer visible
> and even for the guest, the guest might decide to only kill a
> userspace program or even ignore the machine check.
> As this can be a disruptive event nevertheless, we should log this
> not only in the VM debug event (that gets lost after guest shutdown)
> but also on the global KVM event as well as syslog.
> Consolidate the logging and log with loglevel 2 and higher.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>

Acked-by: Hendrik Brueckner <brueckner@linux.ibm.com>