Re: [patch 00/22] genirq/msi, PCI/MSI: Spring cleaning - Part 1

From: Juergen Gross <jgross@suse.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>
Cc: Bjorn Helgaas <helgaas@kernel.org>, Marc Zygnier <maz@kernel.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Kevin Tian <kevin.tian@intel.com>,
	Jason Gunthorpe <jgg@nvidia.com>, Megha Dey <megha.dey@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	linux-pci@vger.kernel.org, Michael Ellerman <mpe@ellerman.id.au>,
	Paul Mackerras <paulus@samba.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	linuxppc-dev@lists.ozlabs.org,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	linux-mips@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	sparclinux@vger.kernel.org, x86@kernel.org,
	xen-devel@lists.xenproject.org, ath11k@lists.infradead.org,
	Wei Liu <wei.liu@kernel.org>,
	linux-hyperv@vger.kernel.org,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>
Subject: Re: [patch 00/22] genirq/msi, PCI/MSI: Spring cleaning - Part 1
Date: Sun, 28 Nov 2021 12:15:03 +0100	[thread overview]
Message-ID: <2b96282e-aa7e-f864-a4fe-a1211605b0d3@suse.com> (raw)
In-Reply-To: <20211126222700.862407977@linutronix.de>

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On 27.11.21 02:18, Thomas Gleixner wrote:
> The [PCI] MSI code has gained quite some warts over time. A recent
> discussion unearthed a shortcoming: the lack of support for expanding
> PCI/MSI-X vectors after initialization of MSI-X.
> 
> PCI/MSI-X has no requirement to setup all vectors when MSI-X is enabled in
> the device. The non-used vectors have just to be masked in the vector
> table. For PCI/MSI this is not possible because the number of vectors
> cannot be changed after initialization.
> 
> The PCI/MSI code, but also the core MSI irq domain code are built around
> the assumption that all required vectors are installed at initialization
> time and freed when the device is shut down by the driver.
> 
> Supporting dynamic expansion at least for MSI-X is important for VFIO so
> that the host side interrupts for passthrough devices can be installed on
> demand.
> 
> This is the first part of a large (total 101 patches) series which
> refactors the [PCI]MSI infrastructure to make runtime expansion of MSI-X
> vectors possible. The last part (10 patches) provide this functionality.
> 
> The first part is mostly a cleanup which consolidates code, moves the PCI
> MSI code into a separate directory and splits it up into several parts.
> 
> No functional change intended except for patch 2/N which changes the
> behaviour of pci_get_vector()/affinity() to get rid of the assumption that
> the provided index is the "index" into the descriptor list instead of using
> it as the actual MSI[X] index as seen by the hardware. This would break
> users of sparse allocated MSI-X entries, but non of them use these
> functions.
> 
> This series is based on 5.16-rc2 and also available via git:
> 
>       git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git msi-v1-part-1

Tested with Xen (PV dom0, PV guest, PVH guest, HVM guest).

You can add my:

Tested-by: Juergen Gross <jgross@suse.com>

Juergen

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