On Wed, Apr 30, 2025 at 05:36:12PM +0200, Niklas Schnelle wrote:
On Tue, 2025-04-29 at 18:42 +0200, Greg Kroah-Hartman wrote:
6.1-stable review patch. If anyone has any objections, please let me know.
From: Niklas Schnelle schnelle@linux.ibm.com
[ Upstream commit aa9f168d55dc47c0de564f7dfe0e90467c9fee71 ]
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... Signed-off-by: Niklas Schnelle schnelle@linux.ibm.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Signed-off-by: Sasha Levin sashal@kernel.org
arch/s390/Kconfig | 4 +--- arch/s390/include/asm/pci.h | 3 +++ arch/s390/pci/Makefile | 2 +- arch/s390/pci/pci_fixup.c | 23 +++++++++++++++++++++++ drivers/s390/net/ism_drv.c | 1 - include/linux/pci_ids.h | 1 + 6 files changed, 29 insertions(+), 5 deletions(-) create mode 100644 arch/s390/pci/pci_fixup.c
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index de575af02ffea..50a4a878bae6d 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -38,9 +38,6 @@ config AUDIT_ARCH config NO_IOPORT_MAP def_bool y -config PCI_QUIRKS
- def_bool n
config ARCH_SUPPORTS_UPROBES def_bool y @@ -213,6 +210,7 @@ config S390 select PCI_DOMAINS if PCI select PCI_MSI if PCI select PCI_MSI_ARCH_FALLBACKS if PCI_MSI
- select PCI_QUIRKS if PCI select SPARSE_IRQ select SWIOTLB select SYSCTL_EXCEPTION_TRACE
diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h index 108e732d7b140..a4e9a6ecbd437 100644 --- a/arch/s390/include/asm/pci.h +++ b/arch/s390/include/asm/pci.h @@ -11,6 +11,9 @@ #include <asm/pci_insn.h> #include <asm/sclp.h> +#define ARCH_GENERIC_PCI_MMAP_RESOURCE 1 +#define arch_can_pci_mmap_wc() 1
#define PCIBIOS_MIN_IO 0x1000 #define PCIBIOS_MIN_MEM 0x10000000 diff --git a/arch/s390/pci/Makefile b/arch/s390/pci/Makefile index eeef68901a15c..2f8dd3f688391 100644 --- a/arch/s390/pci/Makefile +++ b/arch/s390/pci/Makefile @@ -5,5 +5,5 @@ obj-$(CONFIG_PCI) += pci.o pci_irq.o pci_dma.o pci_clp.o pci_sysfs.o \ pci_event.o pci_debug.o pci_insn.o pci_mmio.o \
pci_bus.o pci_kvm_hook.o pci_report.o
pci_bus.o pci_kvm_hook.o pci_report.o pci_fixup.oobj-$(CONFIG_PCI_IOV) += pci_iov.o diff --git a/arch/s390/pci/pci_fixup.c b/arch/s390/pci/pci_fixup.c new file mode 100644 index 0000000000000..35688b6450983 --- /dev/null +++ b/arch/s390/pci/pci_fixup.c @@ -0,0 +1,23 @@ +// 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;
+}
As already noted by others and for other versions the above will cause a build error without also pulling in commit 888bd8322dfc ("s390/pci: Introduce pdev->non_mappable_bars and replace VFIO_PCI_MMAP")
Now dropped, thanks.
greg k-h