git: 40b2111cfaa1 - stable/14 - x86: Add a way to inject artificial MCA events for testing

The branch stable/14 has been updated by jtl:

URL: https://cgit.FreeBSD.org/src/commit/?id=40b2111cfaa1ea9c7ae3487e536e8f75debba700

commit 40b2111cfaa1ea9c7ae3487e536e8f75debba700
Author:     Loic Prylli <lprylli@netflix.com>
AuthorDate: 2025-10-06 17:59:41 +0000
Commit:     Jonathan T. Looney <jtl@FreeBSD.org>
CommitDate: 2025-10-28 19:24:31 +0000

    x86: Add a way to inject artificial MCA events for testing
    
    Reviewed by:    glebius
    Sponsored by:   Netflix
    Differential Revision:  https://reviews.freebsd.org/D52942
    
    (cherry picked from commit 1c2fc62e4a9689961169be7836038acd5f757be1)
---
 sys/x86/x86/mca.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/sys/x86/x86/mca.c b/sys/x86/x86/mca.c
index efe1524eb0e7..a167854e8bbb 100644
--- a/sys/x86/x86/mca.c
+++ b/sys/x86/x86/mca.c
@@ -125,6 +125,17 @@ SYSCTL_INT(_hw_mca, OID_AUTO, erratum383, CTLFLAG_RDTUN,
     &workaround_erratum383, 0,
     "Is the workaround for Erratum 383 on AMD Family 10h processors enabled?");
 
+#ifdef DIAGNOSTIC
+static uint64_t fake_status;
+SYSCTL_U64(_hw_mca, OID_AUTO, fake_status, CTLFLAG_RW,
+    &fake_status, 0,
+    "Insert artificial MCA with given status (testing purpose only)");
+static int fake_bank;
+SYSCTL_INT(_hw_mca, OID_AUTO, fake_bank, CTLFLAG_RW,
+    &fake_bank, 0,
+    "Bank to use for artificial MCAs (testing purpose only)");
+#endif
+
 static STAILQ_HEAD(, mca_internal) mca_freelist;
 static int mca_freecount;
 static STAILQ_HEAD(, mca_internal) mca_records;
@@ -783,8 +794,24 @@ mca_check_status(enum scan_mode mode, uint64_t mcg_cap, int bank,
 	bool mce, recover;
 
 	status = rdmsr(mca_msr_ops.status(bank));
-	if (!(status & MC_STATUS_VAL))
+	if (!(status & MC_STATUS_VAL)) {
+#ifdef DIAGNOSTIC
+		/*
+		 * Check if we have a pending artificial event to generate.
+		 * Note that this is potentially racy with the sysctl. The
+		 * tradeoff is deemed acceptable given the test nature
+		 * of the code.
+		 */
+		if (fake_status && bank == fake_bank) {
+			status = fake_status;
+			fake_status = 0;
+		}
+		if (!(status & MC_STATUS_VAL))
+			return (0);
+#else
 		return (0);
+#endif
+	}
 
 	recover = *recoverablep;
 	mce = mca_is_mce(mcg_cap, status, &recover);