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Re: Program counter stuck at 0xFFFFFFFC when emulating e5500 processor o

From: Philippe Mathieu-Daudé
Subject: Re: Program counter stuck at 0xFFFFFFFC when emulating e5500 processor on T4240-RDB board
Date: Thu, 20 Feb 2020 09:44:13 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1


On 2/20/20 6:40 AM, Wayne Li wrote:
Dear QEMU list members,

No subject: it is unlikely your question get noticed...

Also you didn't Cc'ed the people who might help you (doing that for you):

./scripts/get_maintainer.pl -f target/ppc/cpu-models.c
David Gibson <address@hidden> (maintainer:PowerPC TCG CPUs)
address@hidden (open list:PowerPC TCG CPUs)
address@hidden (open list:All patches CC here)

This will kind of be a repost but I'd like to post my question again because I've gained some more knowledge that makes me feel that my question would be easier to answer.  So we developed a custom-made QEMU VM that emulates a custom machine that has an e5500 processor.  I'm running this VM on a T4240-RDB board which has an e6500 processor and I'm trying to get the VM running with KVM enabled.  The problem I'm having is the program counter refuses to increment at all.  It just stays at the address 0xFFFFFFFC.  On a run without KVM enabled, the VM will also start executing at this same address but the program counter beings to increment immediately.  I know this is a custom QEMU VM and maybe some of the startup stuff we do could be causing problems, but what could possibly stop the program counter from incrementing altogether?

Also, I do have another side question.  When running with KVM enabled, I see the kernel-level ioctl call KVM_RUN running and then returning over and over again (by the way before the VM kinda grinds to a halt I only see QEMU make the KVM_RUN call twice, but the kernel-level ioctl function is being called over and over again for some reason).  And each time the KVM_RUN call returns, the return-from-interrupt takes the VM to the address 0xFFFFFFFC.  What is the KVM_RUN ioctl call used for?  Why is it being called over and over again?  Maybe if I understood this better I'd be able to figure out what's stopping my program counter from incrementing.

-Thanks, Wayne Li

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