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>

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9c9ec08d78c71b4d227beeafab1b82d6434cb5c7..e48741e001476f765e8aba0037a1b386df393683 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -41,9 +41,6 @@ config AUDIT_ARCH
 config NO_IOPORT_MAP
        def_bool y
 
-config PCI_QUIRKS
-       def_bool n
-
 config ARCH_SUPPORTS_UPROBES
        def_bool y
 
@@ -258,6 +255,7 @@ 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 474e1f8d1d3c2fc5685b459cc68b67ac651ea3e9..d2086af3434c0206fe306089fb17b778f8d17bbe 100644 (file)
--- 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 df73c5182990ad3ae4ed5a785953011feb9a093c..1810e0944a4ed9d31261788f0f6eb341e5316546 100644 (file)
--- a/arch/s390/pci/Makefile
+++ b/arch/s390/pci/Makefile
@@ -5,6 +5,6 @@
 
 obj-$(CONFIG_PCI)      += pci.o pci_irq.o pci_clp.o \
                           pci_event.o pci_debug.o pci_insn.o pci_mmio.o \
-                          pci_bus.o pci_kvm_hook.o pci_report.o
+                          pci_bus.o pci_kvm_hook.o pci_report.o pci_fixup.o
 obj-$(CONFIG_PCI_IOV)  += pci_iov.o
 obj-$(CONFIG_SYSFS)    += pci_sysfs.o

diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index d14b8605a32ce1bc132dff225ac433cf3aae9265..88f72745fa59e16df26b1563de27594aac954a78 100644 (file)
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -590,7 +590,6 @@ int pcibios_device_add(struct pci_dev *pdev)
        zpci_zdev_get(zdev);
        if (pdev->is_physfn)
                pdev->no_vf_scan = 1;
-       pdev->non_mappable_bars = 1;
 
        zpci_map_resources(pdev);
 

diff --git a/arch/s390/pci/pci_fixup.c b/arch/s390/pci/pci_fixup.c
new file mode 100644 (file)
index 0000000..35688b6
--- /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;
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_IBM,
+                       PCI_DEVICE_ID_IBM_ISM,
+                       zpci_ism_bar_no_mmap);

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index e36e3ea165d3b2b01d68e53634676cb8c2c40220..d32633ed9fa80c1764724f493b363bfd6cb4f9cf 100644 (file)
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -20,7 +20,6 @@
 MODULE_DESCRIPTION("ISM driver for s390");
 MODULE_LICENSE("GPL");
 
-#define PCI_DEVICE_ID_IBM_ISM 0x04ED
 #define DRV_NAME "ism"
 
 static const struct pci_device_id ism_device_table[] = {

diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
index de5deb1a0118fcf56570d461cbe7a501d4bd0da3..e0cdc290dff5cef39ba491d49008c4153b9b9136 100644 (file)
--- a/include/linux/pci_ids.h
+++ b/include/linux/pci_ids.h
@@ -518,6 +518,7 @@
 #define PCI_DEVICE_ID_IBM_ICOM_V2_ONE_PORT_RVX_ONE_PORT_MDM    0x0251
 #define PCI_DEVICE_ID_IBM_ICOM_V2_ONE_PORT_RVX_ONE_PORT_MDM_PCIE 0x0361
 #define PCI_DEVICE_ID_IBM_ICOM_FOUR_PORT_MODEL 0x252
+#define PCI_DEVICE_ID_IBM_ISM          0x04ed
 
 #define PCI_SUBVENDOR_ID_IBM           0x1014
 #define PCI_SUBDEVICE_ID_IBM_SATURN_SERIAL_ONE_PORT    0x03d4