linux-kernel - Re: PCI IO ECS access is no longer possible for AMD family 17h

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Message-ID: <20250621145015.v7vrlckn6jqtfnb3@pali>
Date: Sat, 21 Jun 2025 16:50:15 +0200
From: Pali Rohár <pali@...nel.org>
To: Rostyslav Khudolii <ros@...c.com>
Cc: Ingo Molnar <mingo@...nel.org>, Yazen Ghannam <yazen.ghannam@....com>,
	Borislav Petkov <bp@...en8.de>,
	Filip Štědronský <p@...narg.cz>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: PCI IO ECS access is no longer possible for AMD family 17h

Hello Rostyslav, you sent an email addressed to me, but you forgot to
put my email address into recipients. So I have not received it.
But luckily, today I found your email by a chance in lkml archive:
https://lore.kernel.org/lkml/CAJDH93uE+foFfRAXVJ48-PYvEUsbpEu_-BVoG-5HsDG66yY7AQ@mail.gmail.com/

On Monday 03 March 2025 10:21:25 Rostyslav Khudolii wrote:
> Hi,
> 
> > Rostyslav, I would like to ask you, do you have patches / updates for
> > enabling the EnableCf8ExtCfg bit for AMD 17h+ family? I could try to
> > adjust my lspci changes for new machines.
> 
> Pali, sorry for the late reply. Do I understand correctly, that even
> though you have access to the ECS via
> the MMCFG you still want the legacy (direct IO) to work for the
> debugging purposes? I can prepare a
> simple patch that will allow you to do so if that's the case.

Yes, I would like to get access to ECS via CF8/CFC direct IO for
debugging purposes, even though MMCFG is enabled and used.

If you can send me a simple patch or any sample / idea how to do it,
I would be very happy. I was not able to figure out how to enable ECS
over CF8/CFC.

Pali