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We don't want user space to be able to map virtio-mem device memory directly (e.g., via /dev/mem) in order to have guarantees that in a sane setup we'll never accidentially access unplugged memory within the device-managed region of a virtio-mem device, just as required by the virtio-spec. As soon as the virtio-mem driver is loaded, the device region is visible in /proc/iomem via the parent device region. From that point on user space is aware of the device region and we want to disallow mapping anything inside that region (where we will dynamically (un)plug memory) until the driver has been unloaded cleanly and e.g., another driver might take over. By creating our parent IORESOURCE_SYSTEM_RAM resource with IORESOURCE_EXCLUSIVE, we will disallow any /dev/mem access to our device region until the driver was unloaded cleanly and removed the parent region. This will work even though only some memory blocks are actually currently added to Linux and appear as busy in the resource tree. So access to the region from user space is only possible a) if we don't load the virtio-mem driver. b) after unloading the virtio-mem driver cleanly. Don't build virtio-mem if access to /dev/mem cannot be restricticted -- if we have CONFIG_DEVMEM=y but CONFIG_STRICT_DEVMEM is not set. Link: https://lkml.kernel.org/r/20210920142856.17758-4-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Cc: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Hanjun Guo <guohanjun@huawei.com> Cc: Jason Wang <jasowang@redhat.com> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
153 lines
4.3 KiB
Plaintext
153 lines
4.3 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config VIRTIO
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tristate
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help
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This option is selected by any driver which implements the virtio
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bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
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or CONFIG_S390_GUEST.
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config ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
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bool
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help
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This option is selected if the architecture may need to enforce
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VIRTIO_F_ACCESS_PLATFORM
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config VIRTIO_PCI_LIB
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tristate
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help
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Modern PCI device implementation. This module implements the
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basic probe and control for devices which are based on modern
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PCI device with possible vendor specific extensions. Any
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module that selects this module must depend on PCI.
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menuconfig VIRTIO_MENU
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bool "Virtio drivers"
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default y
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if VIRTIO_MENU
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config VIRTIO_PCI
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tristate "PCI driver for virtio devices"
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depends on PCI
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select VIRTIO_PCI_LIB
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select VIRTIO
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help
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This driver provides support for virtio based paravirtual device
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drivers over PCI. This requires that your VMM has appropriate PCI
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virtio backends. Most QEMU based VMMs should support these devices
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(like KVM or Xen).
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If unsure, say M.
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config VIRTIO_PCI_LEGACY
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bool "Support for legacy virtio draft 0.9.X and older devices"
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default y
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depends on VIRTIO_PCI
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help
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Virtio PCI Card 0.9.X Draft (circa 2014) and older device support.
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This option enables building a transitional driver, supporting
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both devices conforming to Virtio 1 specification, and legacy devices.
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If disabled, you get a slightly smaller, non-transitional driver,
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with no legacy compatibility.
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So look out into your driveway. Do you have a flying car? If
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so, you can happily disable this option and virtio will not
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break. Otherwise, leave it set. Unless you're testing what
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life will be like in The Future.
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If unsure, say Y.
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config VIRTIO_VDPA
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tristate "vDPA driver for virtio devices"
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depends on VDPA
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select VIRTIO
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help
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This driver provides support for virtio based paravirtual
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device driver over vDPA bus. For this to be useful, you need
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an appropriate vDPA device implementation that operates on a
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physical device to allow the datapath of virtio to be
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offloaded to hardware.
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If unsure, say M.
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config VIRTIO_PMEM
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tristate "Support for virtio pmem driver"
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depends on VIRTIO
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depends on LIBNVDIMM
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help
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This driver provides access to virtio-pmem devices, storage devices
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that are mapped into the physical address space - similar to NVDIMMs
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- with a virtio-based flushing interface.
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If unsure, say Y.
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config VIRTIO_BALLOON
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tristate "Virtio balloon driver"
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depends on VIRTIO
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select MEMORY_BALLOON
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select PAGE_REPORTING
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help
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This driver supports increasing and decreasing the amount
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of memory within a KVM guest.
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If unsure, say M.
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config VIRTIO_MEM
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tristate "Virtio mem driver"
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default m
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depends on X86_64
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depends on VIRTIO
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depends on MEMORY_HOTPLUG
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depends on MEMORY_HOTREMOVE
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depends on CONTIG_ALLOC
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depends on EXCLUSIVE_SYSTEM_RAM
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help
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This driver provides access to virtio-mem paravirtualized memory
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devices, allowing to hotplug and hotunplug memory.
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This driver was only tested under x86-64, but should theoretically
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work on all architectures that support memory hotplug and hotremove.
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If unsure, say M.
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config VIRTIO_INPUT
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tristate "Virtio input driver"
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depends on VIRTIO
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depends on INPUT
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help
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This driver supports virtio input devices such as
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keyboards, mice and tablets.
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If unsure, say M.
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config VIRTIO_MMIO
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tristate "Platform bus driver for memory mapped virtio devices"
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depends on HAS_IOMEM && HAS_DMA
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select VIRTIO
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help
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This drivers provides support for memory mapped virtio
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platform device driver.
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If unsure, say N.
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config VIRTIO_MMIO_CMDLINE_DEVICES
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bool "Memory mapped virtio devices parameter parsing"
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depends on VIRTIO_MMIO
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help
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Allow virtio-mmio devices instantiation via the kernel command line
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or module parameters. Be aware that using incorrect parameters (base
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address in particular) can crash your system - you have been warned.
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See Documentation/admin-guide/kernel-parameters.rst for details.
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If unsure, say 'N'.
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config VIRTIO_DMA_SHARED_BUFFER
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tristate
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depends on DMA_SHARED_BUFFER
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help
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This option adds a flavor of dma buffers that are backed by
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virtio resources.
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endif # VIRTIO_MENU
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