Re: Crash with CXL + TCG on 8.2: Was Re: qemu cxl memory expander shows numa_node -1

[Peter Maydell]

On Fri, 2 Feb 2024 at 16:50, Gregory Price <gregory.price@memverge.com> wrote:
>
> On Fri, Feb 02, 2024 at 04:33:20PM +0000, Peter Maydell wrote:
> > Here we are trying to take an interrupt. This isn't related to the
> > other can_do_io stuff, it's happening because do_ld_mmio_beN assumes
> > it's called with the BQL not held, but in fact there are some
> > situations where we call into the memory subsystem and we do
> > already have the BQL.

> It's bugs all the way down as usual!
> https://xkcd.com/1416/
>
> I'll dig in a little next week to see if there's an easy fix. We can see
> the return address is already 0 going into mmu_translate, so it does
> look unrelated to the patch I threw out - but probably still has to do
> with things being on IO.

Yes, the low level memory accessors only need to take the BQL if the thing
being accessed is an MMIO device. Probably what is wanted is for those
functions to do "take the lock if we don't already have it", something
like hw/core/cpu-common.c:cpu_reset_interrupt() does.

-- PMM