Re: [PATCH for-4.21] x86/hvm: fix reading from 0xe9 IO port if port E9 hack is active

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

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On 10/2/25 3:38 PM, Roger Pau Monné wrote:
> On Thu, Oct 02, 2025 at 11:37:36AM +0100, Andrew Cooper wrote:
>> On 02/10/2025 11:22 am, Roger Pau Monne wrote:
>>> Reading from the E9 port if the emergency console is active should return
>>> 0xe9 according to the documentation from Bochs:
>>>
>>> https://bochs.sourceforge.io/doc/docbook/user/bochsrc.html
>>>
>>> See `port_e9_hack` section description.
>>>
>>> Fix Xen so it also returns the port address.  OSes can use it to detect
>>> whether the emergency console is available or not.
>>>
>>> Fixes: d1bd157fbc9b ("Big merge the HVM full-virtualisation abstractions.")
>>> Signed-off-by: Roger Pau Monné<roger.pau@citrix.com>
>> Reviewed-by: Andrew Cooper<andrew.cooper3@citrix.com>
>>
>> That's been wrong for rather a long time.  How did you find it?
> I came across the documentation above and I didn't remember Xen
> returning any value for reads, which sadly was indeed true.
>
> This was because I had the intention to suggest Alejandro to (also?) use
> the port 0xe9 hack for printing from XTF, which should work for both
> Xen and QEMU.
>
>> CC-ing Oleksii as you've tagged this for 4.21.
> I was told that bugfixes didn't need a release-ack until hard code
> freeze, which is the 31st of October?

I meant until the start of the hard code freeze, which is on October 4.
So there is no need for a release-ack for this patch.

Thanks.

~ Oleksii

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