git: 07007f314700 - main - uart: Don't check SPCR tables if !late_console

The branch main has been updated by cperciva:

URL: https://cgit.FreeBSD.org/src/commit/?id=07007f314700bb556baac724488b4ecbf8e4e29c

commit 07007f314700bb556baac724488b4ecbf8e4e29c
Author:     Colin Percival <cperciva@FreeBSD.org>
AuthorDate: 2022-07-13 00:39:00 +0000
Commit:     Colin Percival <cperciva@FreeBSD.org>
CommitDate: 2022-07-14 06:17:44 +0000

    uart: Don't check SPCR tables if !late_console
    
    On x86 systems, the debug.late_console tunable makes it possible to set
    up the console before we call pmap_bootstrap.  (The tunable is turned
    on by default; setting late_console=0 results in consoles being probed
    early.)
    
    Unfortunately this is not compatible with using the ACPI SPCR table to
    find the console, since consulting ACPI tables requires mapping memory
    addresses.  As such, we skip the call to uart_cpu_acpi_spcr from
    uart_cpu_x86 in the !late_console case.
    
    Reviewed by:    imp
    Sponsored by:   https://www.patreon.com/cperciva
    Differential Revision:  https://reviews.freebsd.org/D35794
---
 sys/amd64/amd64/machdep.c   |  3 +--
 sys/dev/uart/uart_cpu_x86.c | 10 ++++++++--
 sys/i386/i386/machdep.c     |  3 +--
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 9979592acc19..368a3c56c900 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -202,6 +202,7 @@ int cold = 1;
 
 long Maxmem = 0;
 long realmem = 0;
+int late_console = 1;
 
 struct kva_md_info kmi;
 
@@ -1301,7 +1302,6 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 	struct user_segment_descriptor *gdt;
 	struct region_descriptor r_gdt;
 	size_t kstack0_sz;
-	int late_console;
 
 	TSRAW(&thread0, TS_ENTER, __func__, NULL);
 
@@ -1521,7 +1521,6 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 	 * Default to late console initialization to support these drivers.
 	 * This loses mainly printf()s in getmemsize() and early debugging.
 	 */
-	late_console = 1;
 	TUNABLE_INT_FETCH("debug.late_console", &late_console);
 	if (!late_console) {
 		cninit();
diff --git a/sys/dev/uart/uart_cpu_x86.c b/sys/dev/uart/uart_cpu_x86.c
index b9e109646c5d..eeeabde21ebc 100644
--- a/sys/dev/uart/uart_cpu_x86.c
+++ b/sys/dev/uart/uart_cpu_x86.c
@@ -44,6 +44,8 @@ __FBSDID("$FreeBSD$");
 bus_space_tag_t uart_bus_space_io = X86_BUS_SPACE_IO;
 bus_space_tag_t uart_bus_space_mem = X86_BUS_SPACE_MEM;
 
+extern int late_console;
+
 int
 uart_cpu_eqres(struct uart_bas *b1, struct uart_bas *b2)
 {
@@ -66,8 +68,12 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 		return (0);
 
 #ifdef DEV_ACPI
-	/* Check if SPCR can tell us what console to use. */
-	if (uart_cpu_acpi_spcr(devtype, di) == 0)
+	/*
+	 * Check if SPCR can tell us what console to use.  If running with
+	 * !late_console, we haven't set up our own page tables yet, so we
+	 * can't map ACPI tables to look at them.
+	 */
+	if (late_console && uart_cpu_acpi_spcr(devtype, di) == 0)
 		return (0);
 #endif
 
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 43c18042748e..c096ea220146 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -178,6 +178,7 @@ int cold = 1;
 
 long Maxmem = 0;
 long realmem = 0;
+int late_console = 1;
 
 #ifdef PAE
 FEATURE(pae, "Physical Address Extensions");
@@ -1396,7 +1397,6 @@ init386(int first)
 	caddr_t kmdp;
 	vm_offset_t addend;
 	size_t ucode_len;
-	int late_console;
 
 	thread0.td_kstack = proc0kstack;
 	thread0.td_kstack_pages = TD0_KSTACK_PAGES;
@@ -1541,7 +1541,6 @@ init386(int first)
 	 * Default to late console initialization to support these drivers.
 	 * This loses mainly printf()s in getmemsize() and early debugging.
 	 */
-	late_console = 1;
 	TUNABLE_INT_FETCH("debug.late_console", &late_console);
 	if (!late_console) {
 		cninit();