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Message-Id: <20250226-vfio_pci_mmap-v7-2-c5c0f1d26efd@linux.ibm.com>
Date: Wed, 26 Feb 2025 13:07:46 +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 2/3] PCI: s390: Introduce pdev->non_mappable_bars and
replace VFIO_PCI_MMAP
The ability to map PCI resources to user-space is controlled by global
defines. For vfio there is VFIO_PCI_MMAP which is only disabled on s390
and controls mapping of PCI resources using vfio-pci with a fallback
option via the pread()/pwrite() interface.
For the PCI core there is ARCH_GENERIC_PCI_MMAP_RESOURCE which enables
a generic implementation for mapping PCI resources plus the newer sysfs
interface. Then there is HAVE_PCI_MMAP which can be used with custom
definitions of pci_mmap_resource_range() and the historical
/proc/bus/pci interface. Both mechanisms are all or nothing.
For s390 mapping PCI resources is possible and useful for testing and
certain applications such as QEMU's vfio-pci based user-space NVMe
driver. For certain devices, however access to PCI resources via
mappings to user-space is not possible and these must be excluded from
the general PCI resource mapping mechanisms.
Introduce pdev->non_mappable_bars to indicate that a PCI device's BARs
can not be accessed via mappings to user-space. In the future this
enables per-device restrictions of PCI resource mapping.
For now, set this flag for all PCI devices on s390 in line with the
existing, general disable of PCI resource mapping. As s390 is the only
user of the VFI_PCI_MMAP Kconfig options this can already be replaced
with a check of this new flag. Also add similar checks in the other code
protected by HAVE_PCI_MMAP respectively ARCH_GENERIC_PCI_MMAP in
preparation for enabling these for supported devices.
Link: https://lore.kernel.org/lkml/20250212132808.08dcf03c.alex.williamson@redhat.com/
Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
---
arch/s390/pci/pci.c | 1 +
drivers/pci/pci-sysfs.c | 4 ++++
drivers/pci/proc.c | 4 ++++
drivers/vfio/pci/Kconfig | 4 ----
drivers/vfio/pci/vfio_pci_core.c | 2 +-
include/linux/pci.h | 1 +
6 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 88f72745fa59e16df26b1563de27594aac954a78..d14b8605a32ce1bc132dff225ac433cf3aae9265 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -590,6 +590,7 @@ 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/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index b46ce1a2c5542cdea0a3f9df324434fdb7e8a4d2..7373eca0a4943bf896b4a177124e0d4572baec2b 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1257,6 +1257,10 @@ static int pci_create_resource_files(struct pci_dev *pdev)
int i;
int retval;
+ /* Skip devices with non-mappable BARs */
+ if (pdev->non_mappable_bars)
+ return 0;
+
/* Expose the PCI resources from this device as files */
for (i = 0; i < PCI_STD_NUM_BARS; i++) {
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index f967709082d654a101039091b5493b2dec5f57b4..9348a0fb808477ca9be80a8b88bbc036565bc411 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -251,6 +251,10 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
security_locked_down(LOCKDOWN_PCI_ACCESS))
return -EPERM;
+ /* Skip devices with non-mappable BARs */
+ if (dev->non_mappable_bars)
+ return -EINVAL;
+
if (fpriv->mmap_state == pci_mmap_io) {
if (!arch_can_pci_mmap_io())
return -EINVAL;
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index bf50ffa10bdea9e52a9d01cc3d6ee4cade39a08c..c3bcb6911c538286f7985f9c5e938d587fc04b56 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -7,10 +7,6 @@ config VFIO_PCI_CORE
select VFIO_VIRQFD
select IRQ_BYPASS_MANAGER
-config VFIO_PCI_MMAP
- def_bool y if !S390
- depends on VFIO_PCI_CORE
-
config VFIO_PCI_INTX
def_bool y if !S390
depends on VFIO_PCI_CORE
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 586e49efb81be32ccb50ca554a60cec684c37402..c8586d47704c74cf9a5256d65bbf888db72b2f91 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -116,7 +116,7 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_core_device *vdev)
res = &vdev->pdev->resource[bar];
- if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP))
+ if (vdev->pdev->non_mappable_bars)
goto no_mmap;
if (!(res->flags & IORESOURCE_MEM))
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 47b31ad724fa5bf7abd7c3dc572947551b0f2148..7192b9d78d7e337ce6144190325458fe3c0f1696 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -476,6 +476,7 @@ struct pci_dev {
unsigned int no_command_memory:1; /* No PCI_COMMAND_MEMORY */
unsigned int rom_bar_overlap:1; /* ROM BAR disable broken */
unsigned int rom_attr_enabled:1; /* Display of ROM attribute enabled? */
+ unsigned int non_mappable_bars:1; /* BARs can't be mapped to user-space */
pci_dev_flags_t dev_flags;
atomic_t enable_cnt; /* pci_enable_device has been called */
--
2.45.2
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