[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 4/4] xen/uart: enable parsing ACPI SPCR on x86
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Thu, 26 Mar 2026 12:11:58 +0000
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=OneWa1mTlOjw1igtSMmYu+pf/1N4Ajczen9Lk17MhiE=; b=zT1xKhLlN7hXdB2dYg3DV9AWAtZg1fCxuJJCSnG2mW5E6Aw8u54tKHOlzH/4mwx/mRtQVLWd8nZ53jVBTKO1KCsIjslu/YX/gBrjs2D/viMceFo2eqHkhtZoUaeAfAKIHYljf5EBYpBAs9veUBIist7t3hPCQmJ7m1YPU3SlvgsbNwlDvcCbCMqaD3FUnSuwZ+KgvU7cxKjcEbiGNQ/oXOZ4c2q58vHTCAfoaLP4Q7xI7kmg4VuyvCJKutmCaKkKxwaH2CtnXTqz8dEkpvngLO4Vei4pavm89LFJiAdmoGR4DBFzN81HBvjMtBOizuerbShdQyk+wlheMTI9rbzV0Q==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=pWyIBZsxidXZeNybSV8gv+TK/Lri0LajBo8CG8InvjNg1jlufcRv98WONgF6Yf5ag9IU14XGwWT5LxNDNhAfnx5vdCei6xgtpRIHRg+LuY2TMQonHqhss7Ue5F/GSQx2v2oSg/LXUitjyRvingCosIwirhsXZMfE2TwO/5mpD0p/Ki576vlDFlrdDXtFKKLaAaHqzYMBvoJnMiG2Bood85MPzMK0IJ6kuRlI68k7hH63p7i5Y8D+HLDGjf6FwgBdcTnzsdJGeamAzZNVZNCoQA8waGkRLCwxUTKcJBBCPzo/Y+SXTwKOcAiGy/UOPzlIGwigqiEcvwhgpMXZgYVAxg==
- Authentication-results: eu.smtp.expurgate.cloud; dkim=pass header.s=selector1 header.d=citrix.com header.i="@citrix.com" header.h="From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck"
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com;
- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- Delivery-date: Thu, 26 Mar 2026 12:12:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25/03/2026 2:58 pm, Roger Pau Monne wrote:
> Introduce extra logic to allow parsing ACPI tables extra early, and use it
> to parse the ACPI SPCR table and obtain the serial configuration.
>
> This is gated to the "acpi" device type being set in "com1" on the Xen
> command line. Note that there can only be one serial device described in
> the SPCR, so limit it's usage to com1 exclusively for the time being.
>
> I can't test the interrupt information parsing on my system, as the
> interrupt is set to GSI with a value of 0xff, which is outside of the range
> of GSIs available on the system. I've also assumed that the interrupt
> being 0xff is used to signal not interrupt setup (just like the Interrupt
> Pin register on PCI headers).
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> WIP/RFC, not sure whether there's interest in attempting to pursue this
> further on x86. So far the device I have is also exposed on the PCI bus
> aside from SPCR, so using com1=device=amt also works to detect it.
>
> Posting it kind of early to know whether I should try to polish it for
> submission or we are happy with not having this on x86.
I think we should be using SPCR/DBG2 when available. Getting serial
configuration right is always tricky, and we might as well use the help
that Microsoft have forced the OEM/firmware world to provide.
But, I think it should be automatic when the user asked for any kind of
serial. e.g. console=com1 with no com1 configuration. The point of
these tables is to provide an enumeration mechanism where none
previously existed.
~Andrew
|
