Writing to IO port 0x80 in native_io_delay() causes system lockups on
some laptops. This is handled by io_delay_init(), which scans DMI info
and changes io_delay_type on these laptops.
Therefore, calling native_io_delay() / outb_p() / inb_p() / etc. before
io_delay_init() may cause problems there and may constitute a kernel
bug. Warn if this happens.
Signed-off-by: Mateusz Jończyk <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
---
v2: make io_delay_dmi_scanned static
arch/x86/kernel/io_delay.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/io_delay.c b/arch/x86/kernel/io_delay.c
index fdb6506ceaaa..d6deca551a5c 100644
--- a/arch/x86/kernel/io_delay.c
+++ b/arch/x86/kernel/io_delay.c
@@ -29,6 +29,7 @@
#endif
int io_delay_type __read_mostly = DEFAULT_IO_DELAY_TYPE;
+static int io_delay_dmi_scanned __read_mostly;
static int __initdata io_delay_override;
@@ -37,6 +38,8 @@ static int __initdata io_delay_override;
*/
void native_io_delay(void)
{
+ WARN_ON_ONCE(!io_delay_dmi_scanned);
+
switch (io_delay_type) {
default:
case IO_DELAY_TYPE_0X80:
@@ -123,6 +126,8 @@ void __init io_delay_init(void)
{
if (!io_delay_override)
dmi_check_system(io_delay_0xed_port_dmi_table);
+
+ io_delay_dmi_scanned = 1;
}
static int __init io_delay_param(char *s)
--
2.25.1
On Sun, Oct 17, 2021 at 09:25:58PM +0200, Mateusz Jończyk wrote:
> Writing to IO port 0x80 in native_io_delay() causes system lockups on
> some laptops. This is handled by io_delay_init(), which scans DMI info
> and changes io_delay_type on these laptops.
>
> Therefore, calling native_io_delay() / outb_p() / inb_p() / etc. before
> io_delay_init() may cause problems there and may constitute a kernel
> bug. Warn if this happens.
When/how does this happen?
io_delay_init() gets called pretty early in setup_arch()...
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette