git: ee72bc1d1ff8 - main - xen/debug: remove usage of sbuf_{clear,finish}() on drained sbuf

The branch main has been updated by royger:

URL: https://cgit.FreeBSD.org/src/commit/?id=ee72bc1d1ff8aa8704d5861a10ea3514154ff74d

commit ee72bc1d1ff8aa8704d5861a10ea3514154ff74d
Author:     Roger Pau Monné <royger@FreeBSD.org>
AuthorDate: 2024-05-02 13:12:16 +0000
Commit:     Roger Pau Monné <royger@FreeBSD.org>
CommitDate: 2024-05-09 10:50:08 +0000

    xen/debug: remove usage of sbuf_{clear,finish}() on drained sbuf
    
    Using sbuf_clear() on a drained sbuf is explicitly prohibited, and using
    sbuf_finish() after printing a trace leads to a single trace being printed, as
    after calling sbuf_finish() further attempts to use the same sbuf will lead to
    a panic.
    
    While there also switch to using xen_emergency_print() instead of attempting to
    write directly to the hypervisor console.  xen_emergency_print() can be
    implemented per-arch to use a different mechanism than the console hypercall
    (note the default implementation still uses the console hypercall).
    
    Fixes: df62b8a25f47 ('xen: add a handler for the debug interrupt')
    Sponsored by: Cloud Software Group
    Reviewed by: markj
    Differential review: https://reviews.freebsd.org/D45060
---
 sys/dev/xen/debug/debug.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/sys/dev/xen/debug/debug.c b/sys/dev/xen/debug/debug.c
index f17d0c612262..2889b5efdba7 100644
--- a/sys/dev/xen/debug/debug.c
+++ b/sys/dev/xen/debug/debug.c
@@ -58,8 +58,11 @@ static struct sbuf *buf;
 static int
 xendebug_drain(void *arg, const char *str, int len)
 {
-
-	HYPERVISOR_console_write(__DECONST(char *, str), len);
+	/*
+	 * Use xen_emergency_print() instead of xc_printf() to avoid the
+	 * overhead of parsing a format string when it's not needed.
+	 */
+	xen_emergency_print(str, len);
 	return (len);
 }
 
@@ -75,10 +78,9 @@ xendebug_filter(void *arg __unused)
 	stack_save(&st);
 
 	mtx_lock_spin(&lock);
-	sbuf_clear(buf);
 	xc_printf("Printing stack trace vCPU%u\n", XEN_VCPUID());
 	stack_sbuf_print_ddb(buf, &st);
-	sbuf_finish(buf);
+	sbuf_drain(buf);
 	mtx_unlock_spin(&lock);
 #endif