On Fri, Nov 30, 2018 at 11:23:30AM +0100, Stefano Garzarella wrote:
On Thu, Nov 29, 2018 at 5:55 PM Kevin O'Connor kevin@koconnor.net wrote:
Interesting. I tracked down this printf delay - it's due to the save/restore of cpu state when thunking to 16bit mode. (For every character displayed on the screen the code enters 16bit mode to invoke the vgabios and it saves/restores the cr0, gdt, fs, gs, a20, nmi states during that process.) It's trivial to eliminate the calls when there is no vgabios though (see patch below).
Thanks, the patch works, but unfortunately, when I use qemu -nographic, the /etc/sercon-port is set to PORT_SERIAL1 (in src/fw/paravirt.c:623), bypassing the patch. Maybe in QEMU is better to set /etc/sercom-port to 0 when there is no serial port, or when we want a fast boot.
You should be able to use "-device VGA,romfile=" instead.
--- a/src/output.c +++ b/src/output.c @@ -74,6 +74,9 @@ static struct putcinfo debuginfo = { debug_putc }; static void screenc(char c) {
- if (!MODESEGMENT && GET_IVT(0x10).segoff == FUNC16(entry_10).segoff)
// No need to thunk to 16bit mode if vgabios is not presentreturn;Do you plan to commit this patch?
Only if it's useful - does sercon make it not worthwhile?
-Kevin