linux/arch/s390/pci/pci_fixup.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Exceptions for specific devices,
 *
 * Copyright IBM Corp. 2025
 *
 * Author(s):
 *   Niklas Schnelle <schnelle@linux.ibm.com>
 */
#include <linux/pci.h>

static void zpci_ism_bar_no_mmap(struct pci_dev *pdev)
{
	/*
	 * ISM's BAR is special. Drivers written for ISM know
	 * how to handle this but others need to be aware of their
	 * special nature e.g. to prevent attempts to mmap() it.
	 */
	pdev->non_mappable_bars = 1;
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_IBM,
			PCI_DEVICE_ID_IBM_ISM,
			zpci_ism_bar_no_mmap);
s390/pci: Support mmap() of PCI resources except for ISM devices So far s390 does not allow mmap() of PCI resources to user-space via the usual mechanisms, though it does use it for RDMA. For the PCI sysfs resource files and /proc/bus/pci it defines neither HAVE_PCI_MMAP nor ARCH_GENERIC_PCI_MMAP_RESOURCE. For vfio-pci s390 previously relied on disabled VFIO_PCI_MMAP and now relies on setting pdev->non_mappable_bars for all devices. This is partly because access to mapped PCI resources from user-space requires special PCI load/store memory-I/O (MIO) instructions, or the special MMIO syscalls when these are not available. Still, such access is possible and useful not just for RDMA, in fact not being able to mmap() PCI resources has previously caused extra work when testing devices. One thing that doesn't work with PCI resources mapped to user-space though is the s390 specific virtual ISM device. Not only because the BAR size of 256 TiB prevents mapping the whole BAR but also because access requires use of the legacy PCI instructions which are not accessible to user-space on systems with the newer MIO PCI instructions. Now with the pdev->non_mappable_bars flag ISM can be excluded from mapping its resources while making this functionality available for all other PCI devices. To this end introduce a minimal implementation of PCI_QUIRKS and use that to set pdev->non_mappable_bars for ISM devices only. Then also set ARCH_GENERIC_PCI_MMAP_RESOURCE to take advantage of the generic implementation of pci_mmap_resource_range() enabling only the newer sysfs mmap() interface. This follows the recommendation in Documentation/PCI/sysfs-pci.rst. Link: https://lore.kernel.org/r/20250226-vfio_pci_mmap-v7-3-c5c0f1d26efd@linux.ibm.com Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> 2025-02-26 13:07:47 +01:00			`// SPDX-License-Identifier: GPL-2.0`
			`/*`
			`* Exceptions for specific devices,`
			`*`
			`* Copyright IBM Corp. 2025`
			`*`
			`* Author(s):`
			`* Niklas Schnelle <schnelle@linux.ibm.com>`
			`*/`
			`#include <linux/pci.h>`

			`static void zpci_ism_bar_no_mmap(struct pci_dev *pdev)`
			`{`
			`/*`
			`* ISM's BAR is special. Drivers written for ISM know`
			`* how to handle this but others need to be aware of their`
			`* special nature e.g. to prevent attempts to mmap() it.`
			`*/`
			`pdev->non_mappable_bars = 1;`
			`}`
			`DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_IBM,`
			`PCI_DEVICE_ID_IBM_ISM,`
			`zpci_ism_bar_no_mmap);`