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When CONFIG_PCI_P2PDMA=y (which is basically enabled on all large x86 distros), it maps the PFN's via a ZONE_DEVICE mapping using devm_memremap_pages(). The mapped virtual address range corresponds to the pci_resource_start() of the BAR address and size corresponding to the BAR length. When KASLR is enabled, the direct map range of the kernel is reduced to the size of physical memory plus additional padding. If the BAR address is beyond this limit, PCI peer to peer DMA mappings fail. Fix this by not shrinking the size of the direct map when CONFIG_PCI_P2PDMA=y. This reduces the total available entropy, but it's better than the current work around of having to disable KASLR completely. [ mingo: Clarified the changelog to point out the broad impact ... ] Signed-off-by: Balbir Singh <balbirs@nvidia.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Kees Cook <kees@kernel.org> Acked-by: Bjorn Helgaas <bhelgaas@google.com> # drivers/pci/Kconfig Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Link: https://lore.kernel.org/lkml/20250206023201.1481957-1-balbirs@nvidia.com/ Link: https://lore.kernel.org/r/20250206234234.1912585-1-balbirs@nvidia.com -- arch/x86/mm/kaslr.c | 10 ++++++++-- drivers/pci/Kconfig | 6 ++++++ 2 files changed, 14 insertions(+), 2 deletions(-) |
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| .. | ||
| controller | ||
| endpoint | ||
| hotplug | ||
| msi | ||
| pcie | ||
| pwrctrl | ||
| switch | ||
| access.c | ||
| ats.c | ||
| bus.c | ||
| devres.c | ||
| doe.c | ||
| ecam.c | ||
| host-bridge.c | ||
| iomap.c | ||
| iov.c | ||
| irq.c | ||
| Kconfig | ||
| Makefile | ||
| mmap.c | ||
| npem.c | ||
| of_property.c | ||
| of.c | ||
| p2pdma.c | ||
| pci-acpi.c | ||
| pci-bridge-emul.c | ||
| pci-bridge-emul.h | ||
| pci-driver.c | ||
| pci-label.c | ||
| pci-mid.c | ||
| pci-pf-stub.c | ||
| pci-stub.c | ||
| pci-sysfs.c | ||
| pci.c | ||
| pci.h | ||
| probe.c | ||
| proc.c | ||
| quirks.c | ||
| remove.c | ||
| rom.c | ||
| search.c | ||
| setup-bus.c | ||
| setup-res.c | ||
| slot.c | ||
| syscall.c | ||
| tph.c | ||
| vc.c | ||
| vgaarb.c | ||
| vpd.c | ||
| xen-pcifront.c | ||