uml: disable kmod-8250-serial

The driver tries to access ioports (0x2f9!!) which UML doesn't have.
This causes lots of warnings to appear on boot:

| WARNING: CPU: 0 PID: 1 at lib/logic_iomem.c:188 serial8250_config_port+0x20a/0x1260
| Invalid writeqb of 0xff at address 2f9
| Modules linked in:
| CPU: 0 UID: 0 PID: 1 Comm: swapper Tainted: G        W          6.12.25 #0
| Tainted: [W]=WARN
| Stack:
| Call Trace:
|  [<60001000>] ? set_reset_devices+0x0/0x16
|  [<60452cba>] ? serial8250_config_port+0x20a/0x1260
|  [<6071e91f>] ? dump_stack_lvl+0x55/0x71
|  [<606e127c>] ? _printk+0x0/0x4f
|  [<60044bbb>] ? __warn+0x11b/0x120
|  [<6003b5d0>] ? um_set_signals+0x0/0x40
|  [<606de721>] ? warn_slowpath_fmt+0x81/0x8c
|  [<606de6a0>] ? warn_slowpath_fmt+0x0/0x8c
|  [<60452cba>] ? serial8250_config_port+0x20a/0x1260

(they are even recursive!)

Now, the situation gets more confusing. Because from what I can tell,
this was seemingly done intenionally. Upstream patches in related areas:

|commit ddd268c42871b78c75e12a5c28207fb481138f41
|Author: Niklas Schnelle <schnelle@linux.ibm.com>
|Date:   Wed Apr 3 14:43:00 2024 +0200
|
|    um: Select HAS_IOREMAP for UML_IOMEM_EMULATION
|
|    In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
|    compile time. UML supports these via its UML_IOMEM_EMULATION so let that
|    select HAS_IOPORT and also reflect this in NO_IOPORT_MAP.

hint that there's ongoing work in this area. But unfortunately, this future
hasn't arrived yet. Once this future arrives, please nuke this patch.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

diff --git a/package/kernel/linux/modules/other.mk b/package/kernel/linux/modules/other.mk
index 8da6216cbf244a7fc109b944e79953d9694c2287..61e395813b6b6e127f6f706f6f9550be35d5481d 100644 (file)
--- a/package/kernel/linux/modules/other.mk
+++ b/package/kernel/linux/modules/other.mk
@@ -563,6 +563,7 @@ $(eval $(call KernelPackage,reed-solomon))
 define KernelPackage/serial-8250
   SUBMENU:=$(OTHER_MENU)
   TITLE:=8250 UARTs
+  DEPENDS:=@!TARGET_uml
   KCONFIG:= CONFIG_SERIAL_8250 \
        CONFIG_SERIAL_8250_PCI \
        CONFIG_SERIAL_8250_NR_UARTS=16 \

diff --git a/target/linux/uml/config-6.12 b/target/linux/uml/config-6.12
index 273c10ea4f28879d8097f5d985b8b2bd17f1e2bd..d4f42f88b01a3dcf4f8cf1ed182b5c2b36091c86 100644 (file)
--- a/target/linux/uml/config-6.12
+++ b/target/linux/uml/config-6.12
@@ -107,6 +107,7 @@ CONFIG_RANDSTRUCT_NONE=y
 CONFIG_RD_BZIP2=y
 CONFIG_RD_GZIP=y
 CONFIG_RELAY=y
+# CONFIG_SERIAL_8250 is not set
 CONFIG_SG_POOL=y
 CONFIG_SOFT_WATCHDOG=m
 CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU=y