This fixes the following problems: 1) Typematic-repeat of 'enter' gives warning message. 2) Use of 'keypad enter' gives warning message. 3) Lag on the order of seconds between "break" and "make" when expecting the enter "break" code. Seen under virtualized environments such as VMware ESX.
Explanations: 1) Holding down 'enter' will not set a repeating sequence of 0x1c(make)-0x9c(make), but a repeating sequence of make codes, followed by one break code when the key is released. Thus, it's wrong to expect the break code after seeing the 'enter' make code. 2) Keypad enter generates different make/break, namely 0xe0 0x1c and 0xe0 0x9c. The 'generic' logic handles the 0xe0 escape already, but the special 'enter' logic always expects '0x9c' and not '0xe0 0x9c', so you get a warning message, again. 3) When expecting the 'enter' break code, the code polls the status register in a tight loop, like so - > while ((inb(KBD_STATUS_REG) & KBD_STAT_OBF) == 0); However, it really should do something like - > while ((inb(KBD_STATUS_REG) & KBD_STAT_OBF) == 0) > cpu_relax(); /* pause */ Basically, it's a common optimization to have a fast path for accessing often accessed and slow changing I/O in a virtualized environment. The tight spinning in KDB seems to run against the logic by ESX keyboard virtualization code to detect when the fast path or the slow path should be used to satisfy the keyboard status read, leading to multi-second timeouts before the 'real' status comes through. Without knowing ESX internals, it's hard to say if this is an ESX bug or not, but letting the VM be explicitely descheduled seems to resolve the problem. I've seen something similar with shared MMIO buffers with VMs on Hyper-V. Anyway, given (3), (2) and (1), we might as well blow away the entire special casing for 'enter'. The break codes will already be handled correctly, and we get rid of the bugs with repeat enters and keypad enter key. And of course, there is no need to AND with 0x7f when checking for 'enter', because we'll never ever get to this code with a break code (checked for much earlier). I tried to figure out the history behind the 'enter' key special casing code, and it seems to have come from whatever the original KDB patch was. Perhaps someone can chime in. Tested on ESX 5.0 and QEMU. Signed-off-by: Andrei Warkentin <[email protected]> --- kernel/debug/kdb/kdb_keyboard.c | 28 +--------------------------- 1 files changed, 1 insertions(+), 27 deletions(-) diff --git a/kernel/debug/kdb/kdb_keyboard.c b/kernel/debug/kdb/kdb_keyboard.c index 4bca634..ed4a2f9 100644 --- a/kernel/debug/kdb/kdb_keyboard.c +++ b/kernel/debug/kdb/kdb_keyboard.c @@ -178,34 +178,8 @@ int kdb_get_kbd_char(void) return -1; /* ignore unprintables */ } - if ((scancode & 0x7f) == 0x1c) { - /* - * enter key. All done. Absorb the release scancode. - */ - while ((inb(KBD_STATUS_REG) & KBD_STAT_OBF) == 0) - ; - - /* - * Fetch the scancode - */ - scancode = inb(KBD_DATA_REG); - scanstatus = inb(KBD_STATUS_REG); - - while (scanstatus & KBD_STAT_MOUSE_OBF) { - scancode = inb(KBD_DATA_REG); - scanstatus = inb(KBD_STATUS_REG); - } - - if (scancode != 0x9c) { - /* - * Wasn't an enter-release, why not? - */ - kdb_printf("kdb: expected enter got 0x%x status 0x%x\n", - scancode, scanstatus); - } - + if (scancode == 0x1c) return 13; - } return keychar & 0xff; } -- 1.7.4.1 ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Kgdb-bugreport mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
