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Message-Id: <20250226-vfio_pci_mmap-v7-3-c5c0f1d26efd@linux.ibm.com>
Date: Wed, 26 Feb 2025 13:07:47 +0100
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Bjorn Helgaas <helgaas@...nel.org>, Christoph Hellwig <hch@....de>,
Alexandra Winter <wintera@...ux.ibm.com>,
Alex Williamson <alex.williamson@...hat.com>,
Gerd Bayer <gbayer@...ux.ibm.com>,
Matthew Rosato <mjrosato@...ux.ibm.com>,
Jason Gunthorpe <jgg@...pe.ca>,
Thorsten Winkler <twinkler@...ux.ibm.com>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Julian Ruess <julianr@...ux.ibm.com>, Halil Pasic <pasic@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>,
Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
linux-pci@...r.kernel.org, Niklas Schnelle <schnelle@...ux.ibm.com>
Subject: [PATCH v7 3/3] PCI: s390: 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.
Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
---
arch/s390/Kconfig | 4 +---
arch/s390/include/asm/pci.h | 3 +++
arch/s390/pci/Makefile | 2 +-
arch/s390/pci/pci.c | 1 -
arch/s390/pci/pci_fixup.c | 23 +++++++++++++++++++++++
drivers/s390/net/ism_drv.c | 1 -
include/linux/pci_ids.h | 1 +
7 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9c9ec08d78c71b4d227beeafab1b82d6434cb5c7..e48741e001476f765e8aba0037a1b386df393683 100644
--- 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
--- 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
--- 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
--- 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
index 0000000000000000000000000000000000000000..35688b645098329f082d0c40cc8c59231c390eaa
--- /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@...ux.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 2f34761e64135c154b5193f870c27753481feed0..60ed70a39d2ccade0dcd73207a30551f4bd1203a 100644
--- 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 1a2594a38199fe77cbcabcfa57dc407fc66ddb44..3efb45beabf8ad46d1c28053fedb776b5027ddef 100644
--- 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
--
2.45.2
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