git: 572cd669d699 - main - hwpmc: handle delayed IBS NMIs on Zen 6

The branch main has been updated by mhorne:

URL: https://cgit.FreeBSD.org/src/commit/?id=572cd669d6997b759084191007f3744a3610b529

commit 572cd669d6997b759084191007f3744a3610b529
Author:     Andre Silva <andasilv@amd.com>
AuthorDate: 2026-10-06 18:42:35 +0000
Commit:     Mitchell Horne <mhorne@FreeBSD.org>
CommitDate: 2026-10-06 18:53:44 +0000

    hwpmc: handle delayed IBS NMIs on Zen 6
    
    On Zen 6, an extra IBS NMI can arrive after later samples. Keep the
    credit until the empty NMI arrives, and handle fetch and op samples when
    both are ready.
    
    Reviewed by:    mhorne
    Fixes:  34b00ed041a4 ("hwpmc: fix IBS fetch and op NMI handling")
    Fixes:  e51ef8ae490f ("hwpmc: Initial support for AMD IBS")
    Sponsored by:   AMD
    Differential Revision:  https://reviews.freebsd.org/D60367
---
 sys/dev/hwpmc/hwpmc_ibs.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/sys/dev/hwpmc/hwpmc_ibs.c b/sys/dev/hwpmc/hwpmc_ibs.c
index be981b0c7a07..60e7323dbcb8 100644
--- a/sys/dev/hwpmc/hwpmc_ibs.c
+++ b/sys/dev/hwpmc/hwpmc_ibs.c
@@ -48,6 +48,7 @@
 #include <machine/specialreg.h>
 
 #define	IBS_STOP_ITER		50 /* Stopping iterations */
+#define	IBS_NMI_CREDIT_MAX	2  /* Max owed IBS NMIs per CPU */
 
 /* AMD IBS PMCs */
 struct ibs_descr {
@@ -97,7 +98,7 @@ SYSCTL_U64(_kern_hwpmc, OID_AUTO, ibs_op_ctl2_extra_mask, CTLFLAG_RDTUN,
 
 struct ibs_cpu {
 	int		pc_status;
-	int		pc_nmi_credit;	/* latched NMIs already serviced */
+	int		pc_nmi_credit;	/* owed NMIs already serviced */
 	struct pmc_hw	pc_ibspmcs[IBS_NPMCS];
 };
 static struct ibs_cpu **ibs_pcpu;
@@ -725,13 +726,21 @@ pmc_ibs_intr(struct trapframe *tf)
 	}
 
 	/*
-	 * When both units were serviced, the second unit's NMI may still be
-	 * latched and will arrive with no valid bit set.  Claim that one
-	 * NMI so it is not reported as unknown.
+	 * When both units were serviced, the second unit's NMI is still
+	 * owed and will arrive with no valid bit set.  It is not always
+	 * the next NMI: on Zen 6 one or more NMIs carrying a single new
+	 * sample can arrive first, and those may carry both samples again.
+	 * Count the owed NMIs and let each NMI with no valid bit consume one,
+	 * so they are not reported as unknown.  Cap the count, since every
+	 * leftover credit would hide a genuine unknown NMI later.
 	 */
-	if (retval == 0 && pac->pc_nmi_credit != 0)
+	if (retval == 2) {
+		if (pac->pc_nmi_credit < IBS_NMI_CREDIT_MAX)
+			pac->pc_nmi_credit++;
+	} else if (retval == 0 && pac->pc_nmi_credit > 0) {
+		pac->pc_nmi_credit--;
 		retval = 1;
-	pac->pc_nmi_credit = (retval == 2);
+	}
 	if (retval > 1)
 		retval = 1;