Re: arm64 syzbot instances

On Mon, Mar 15, 2021 at 10:45 AM John Garry [off-list ref] wrote:

quoted

quoted

It does not happen too often on syzbot so far, so let's try to do the
right thing first.
I've filed: https://bugs.launchpad.net/qemu/+bug/1918917
with a link to this thread. To be fair, I don't fully understand what
I am talking about, I hope I proxied your description properly.

Thanks, looks good. I provided a little more detail in a comment there.

         Arnd
.

 From looking at the bug report, my impression is that this is a qemu
issue, as the logical IO space is mapped to the PCI host bridge IO
space, and qemu does not handle accesses to that CPU addressable region
at all. As Arnd said.

However, we really should not be accessing logical IO ports 0 or 0x2f8
at all via ttyS3 if not enumerated from PCI device at that logical IO
port. That is what I think anyway, as who knows what device - if any -
really exists at that location. That is why I had this patch to just
stop accesses to legacy IO port regions on arm64:

https://lore.kernel.org/lkml/1610729929-188490-2-git-send-email-john.garry@huawei.com/ (local)

Hi John,

Thanks for the info.

The patch is from January, but it's not merged yet, right?
It will fix the crash we see, right?

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