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Re: [PATCH v3 00/18] hw/ide: Untangle ISA/PCI abuses of ide_init_ioport(

From: BALATON Zoltan
Subject: Re: [PATCH v3 00/18] hw/ide: Untangle ISA/PCI abuses of ide_init_ioport()
Date: Fri, 3 Mar 2023 13:47:32 +0100 (CET)

On Fri, 3 Mar 2023, David Woodhouse wrote:
On 2 March 2023 22:40:40 GMT, "Philippe Mathieu-Daudé" <philmd@linaro.org> 
Since v2: rebased

I'm posting this series as it to not block Bernhard's PIIX
cleanup work. I don't have code change planned, but eventually
reword / improve commit descriptions.

Tested commit after commit to be sure it is bisectable. Sadly
this was before Zoltan & Thomas report a problem with commit
bb98e0f59c ("hw/isa/vt82c686: Remove intermediate IRQ forwarder").

However much I stare at the partial revert which fixes it, I just cannot believe that the change could make any difference at all. There's got to be something weird going on there.

I was going to ask if the level mode for the PIT made any difference, but this is the output IRQ from the PIT to the CPU itself so I don't see how it would.

This is independent of the ltim patch and I've found this even before you've sent that patch as this is in my v5 series which you've replied to. I've found this problem before when I've first written this model back in 2019 and did not understand why it's needed but as now shown also with the prep machine there's some other problem somewhere that makes this necessary. As the way we had before works for the last few years reverting it is the safest bet now but we can try to find out and clean up eventually.

Would like to see a report with tracing from pic_update_irq, the CPU interrupt "handler" and the intermediate IRQ handler. With the intermediate present and without it. To compare the two.

I'll try to collect such trace when I'll have time but if you want to experiment debian 8.11.0 netinstall cd should boot either with -kernel or with the -bios pegasos2.rom (type boot cd install/pegasos at the ok prompt in that case but the rom needs to be extracted from an updater as it's not freely distributable). I think Thomas Huth also reproduced the same with prep or 40p firmware after a similar change on that machine now.

In any case it's unrelated to level sensitive mode which is only needed by MorphOS on pegasos2 to fix simultaneous interrupts e.g.with sound and USB or PCI cards which all share IRQ9 on that machine. Other guests don't even enable that ltim bit so it should not affect anything else.


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