git: 3330226fd33a - main - vmm: Normalize a zero PIT count before starting channel 0

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=3330226fd33ae6b747c9edc97315244360ad5e54

commit 3330226fd33ae6b747c9edc97315244360ad5e54
Author:     Hayzam Sherif <hayzam@gmail.com>
AuthorDate: 2026-09-21 16:33:36 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2026-09-21 16:35:58 +0000

    vmm: Normalize a zero PIT count before starting channel 0
    
    pit_timer_start_cntr0() does not schedule a callout when the initial
    count is zero.  The counter write handler normalizes a programmed zero
    count only after calling it, leaving an initially unarmed channel 0
    without a scheduled timer event.
    
    Move the existing normalization before the timer-start call.  Retain the
    historical 0xffff representation of a zero count.
    
    Reviewed by:    markj
    MFC after:      2 weeks
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D59749
---
 sys/amd64/vmm/io/vatpit.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sys/amd64/vmm/io/vatpit.c b/sys/amd64/vmm/io/vatpit.c
index 31b6c2ad0f89..595c2e070c7a 100644
--- a/sys/amd64/vmm/io/vatpit.c
+++ b/sys/amd64/vmm/io/vatpit.c
@@ -401,14 +401,14 @@ vatpit_handler(struct vm *vm, bool in, int port, int bytes, uint32_t *eax)
 			c->frbyte = 0;
 			c->crbyte = 0;
 			c->initial = c->cr[0] | (uint16_t)c->cr[1] << 8;
+			if (c->initial == 0)
+				c->initial = 0xffff;
 			binuptime(&c->now_bt);
 			/* Start an interval timer for channel 0 */
 			if (port == TIMER_CNTR0) {
 				c->callout_bt = c->now_bt;
 				pit_timer_start_cntr0(vatpit);
 			}
-			if (c->initial == 0)
-				c->initial = 0xffff;
 		}
 	}
 	VATPIT_UNLOCK(vatpit);