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Re: [PATCH v3 1/8] serial: fake IRQ-regs context in poll handlers
- To: Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 13 Feb 2024 08:45:54 +0100
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- Cc: Julien Grall <julien@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 13 Feb 2024 07:46:04 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13.02.2024 04:43, Marek Marczykowski wrote:
> On Mon, Feb 12, 2024 at 10:04:38AM +0100, Jan Beulich wrote:
>> On 08.02.2024 23:00, Julien Grall wrote:
>>> On 05/02/2024 13:27, Jan Beulich wrote:
>>>> In preparation of dropping the register parameters from
>>>> serial_[rt]x_interrupt() and in turn from IRQ handler functions,
>>>> register state needs making available another way for the few key
>>>> handlers which need it. Fake IRQ-like state.
>>>>
>>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>> ---
>>>> The use of guest_cpu_user_regs() in dbc_uart_poll() is inconsistent with
>>>> other console poll functions we have, and it's unclear whether that's
>>>> actually generally correct.
>>>
>>> Is it? Looking at ns16550_poll() we would pass guest_user_regs() if
>>> run_in_exception() doesn't exist. But looking at the caller, no-on seems
>>> to care about the 'regs'. So is this just a latent bug?
>>
>> What do you mean by "doesn't exist"? ns16550_poll() assumes it exists.
>> And I can spot any use of guest_user_regs() on the respective generic
>> or Arm-specific bug.c paths.
>>
>>> BTW, do you have an idea why the poll function is not run in an
>>> exception handler?
>>
>> "The poll function" being which one? If you mean the one in xhci-dbc.c
>> then that's why I had Cc-ed Marek. Moving him to To: - maybe that
>> manages to finally catch his attention.
>
> TBH, I don't know. That's part of the original xue patch at
> https://github.com/connojd/xue/blob/master/patches/xen-xue-dbgp.patch
> and it works for me as it is.
"Works" meaning what? Doesn't crash on you? Or does also provide
sensible output in _all_ cases (i.e. including when e.g. the poll
happens to run on an idle vCPU)?
Jan
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