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

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Message-ID: <20250715170637.mtplp7s73zwdbjay@pali>
Date: Tue, 15 Jul 2025 19:06:37 +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

On Tuesday 15 July 2025 12:43:16 Rostyslav Khudolii wrote:
> >
> > 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.
> >
> 
> Hi Pali,
> I'm sorry for the late reply.
> 
> If I understand your request correctly, all you need to do  is patch
> the pci_enable_pci_io_ecs() function to use
> the different register to set EnableCF8ExtCfg: D18F4x044.
> 
> Regards,
> Ros

Hello, thank you for information.

Just I would like to know, where did you find information that the
EnableCF8ExtCfg register was moved to D18F4x044? It is documented in
some AMD specification?

I did not find anything regarding this change.

Pali