linux-kernel - Re: [PATCH 16/16] x86/amd_smn: Add support for debugfs access to SMN registers

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Message-ID: <f4b2c3b7-187c-4339-a82b-c6126edbd3ee@amd.com>
Date: Tue, 5 Nov 2024 14:53:07 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Yazen Ghannam
 <yazen.ghannam@....com>, linux-edac@...r.kernel.org,
 linux-kernel@...r.kernel.org, tony.luck@...el.com, x86@...nel.org,
 avadhut.naik@....com, john.allen@....com, Shyam-sundar.S-k@....com,
 richard.gong@....com, jdelvare@...e.com, linux@...ck-us.net,
 clemens@...isch.de, hdegoede@...hat.com, ilpo.jarvinen@...ux.intel.com,
 linux-pci@...r.kernel.org, linux-hwmon@...r.kernel.org,
 platform-driver-x86@...r.kernel.org, naveenkrishna.chatradhi@....com,
 carlos.bilbao.osdev@...il.com
Subject: Re: [PATCH 16/16] x86/amd_smn: Add support for debugfs access to SMN
 registers

On 11/5/2024 13:59, Borislav Petkov wrote:
> On Tue, Nov 05, 2024 at 01:56:23PM -0600, Mario Limonciello wrote:
>> OK got it.  Considering that I think after this series lands we need to
>> re-open the conversation about PCI config space access to userspace;
>> particularly on regions that have been marked as exclusions.
> 
> I could imagine a patch that goes and requests those regions exclusively if
> luserspace has no business poking there.
> 

Take look at what pci_write_config() does today.  It basically shows a 
warning and taints but lets userspace proceed.

commit 278294798ac91 ("PCI: Allow drivers to request exclusive config 
regions") and the matching mailing list thread linked from the commit 
message have some history from it.

I'd personally like to see that taint turned into an "return -EACCES" 
instead. But given the discussion linked in that commit, I think it 
should be a follow up rather than part of this series.