linux-kernel - Re: [PATCH] PCI: vmd: Remove MSI-X check on child devices

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250812190036.GA199875@bhelgaas>
Date: Tue, 12 Aug 2025 14:00:36 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Nam Cao <namcao@...utronix.de>
Cc: Keith Busch <kbusch@...nel.org>,
	Nirmal Patel <nirmal.patel@...ux.intel.com>,
	Jonathan Derrick <jonathan.derrick@...ux.dev>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczy´nski <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ammar Faizi <ammarfaizi2@...weeb.org>
Subject: Re: [PATCH] PCI: vmd: Remove MSI-X check on child devices

On Tue, Aug 12, 2025 at 08:22:09PM +0200, Nam Cao wrote:
> On Tue, Aug 12, 2025 at 11:30:15AM -0500, Bjorn Helgaas wrote:
> > On Tue, Aug 12, 2025 at 08:49:50AM -0600, Keith Busch wrote:
> > > The doc you linked is riddled with errors. The original vmd commit
> > > message is more accurate: VMD domains support child devices with MSI and
> > > MSI-x interrupts. The VMD device can't even tell the difference which
> > > one the device is using. It just manipulates messages sent to the usual
> > > APIC address 0xfeeXXXXX.
> > 
> > Thanks, Keith!  I updated the commit log like this:
> > 
> >   d7d8ab87e3e7 ("PCI: vmd: Switch to msi_create_parent_irq_domain()") added a
> >   WARN_ON sanity check that child devices support MSI-X, because VMD document
> >   says [1]:
> > 
> >     Intel VMD only supports MSIx Interrupts from child devices and therefore
> >     the BIOS must enable PCIe Hot Plug and MSIx interrups [sic].
> > 
> >   However, the VMD device can't even tell the difference between a child
> >   device using MSI and one using MSI-X.  Per 185a383ada2e ("x86/PCI: Add
> >   driver for Intel Volume Management Device (VMD)"), VMD does not support
> >   INTx interrupts, but does support child devices using either MSI or MSI-X.
> > 
> >   Remove the sanity check to avoid the unnecessary WARN_ON reported by Ammar.
> 
> Minor correction, it is not just an unnecessary WARN_ON, but child devices'
> drivers couldn't enable MSI at all.
> 
> So perhaps something like "Remove the sanity check to allow child devices
> which only support MSI".

Thanks, updated.