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List-Post: List-Help: List-Subscribe: , Cc: Alex Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/20/19 6:25 AM, Philippe Mathieu-Daud=C3=A9 wrote: > [cross posting QEMU & SeaBIOS] >=20 > Hello, >=20 > I'v been looking at a QEMU bug report [1] which bisection resulted in a > SeaBIOS commit: >=20 > 4a6dbcea3e412fe12effa2f812f50dd7eae90955 is the first bad commit > commit 4a6dbcea3e412fe12effa2f812f50dd7eae90955 > Author: Nikolay Nikolov > Date: Sun Feb 4 17:27:01 2018 +0200 >=20 > floppy: Use timer_check() in floppy_wait_irq() >=20 > Use timer_check() instead of using floppy_motor_counter in BDA for = the > timeout check in floppy_wait_irq(). >=20 > The problem with using floppy_motor_counter was that, after it reac= hes > 0, it immediately stops the floppy motors, which is not what is > supposed to happen on real hardware. Instead, after a timeout (like= in > the end of every floppy operation, regardless of the result - succe= ss, > timeout or error), the floppy motors must be kept spinning for > additional 2 seconds (the FLOPPY_MOTOR_TICKS). So, now the > floppy_motor_counter is initialized to 255 (the max value) in the > beginning of the floppy operation. For IRQ timeouts, a different > timeout is used, specified by the new FLOPPY_IRQ_TIMEOUT constant > (currently set to 5 seconds - a fairly conservative value, but shou= ld > work reliably on most floppies). >=20 > After the floppy operation, floppy_drive_pio() resets the > floppy_motor_counter to 2 seconds (FLOPPY_MOTOR_TICKS). >=20 > This is also consistent with what other PC BIOSes do. >=20 >=20 > This commit improve behavior with real hardware, so maybe QEMU is not > modelling something or modelling it incorrectly? >=20 >=20 > Regards, >=20 > Phil. >=20 >=20 > PD: How to reproduce: >=20 > - Download Windows 98 SE floppy image from [2] >=20 > - Run QEMU using the 'isapc' machine: >=20 > $ qemu-system-i386 -M isapc \ > -fda Windows\ 98\ Second\ Edition\ Boot.img >=20 > SeaBIOS (version rel-1.11.0-11-g4a6dbce-prebuilt.qemu.org) > Booting from Floppy... > Boot failed: could not read the boot disk >=20 > [1] https://bugs.launchpad.net/qemu/+bug/1840719 > [2] https://winworldpc.com/download/417d71c2-ae18-c39a-11c3-a4e284a2c3a= 5 >=20 Well, that's unfortunate. What version of QEMU shipped the SeaBIOS that caused the regression?