Document PCI_HP and PCI_IOV kernel options and various tunables in pci(4).
Describe PCI-related kernel options for HotPlug and SR-IOV support in the pci(4) manual page. While here, add a section describing the various tunables supported by the PCI bus driver as well. Reviewed by: wblock MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D7754
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John Baldwin
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@ -24,21 +24,47 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 9, 2016
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.Dd September 8, 2016
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.Dt PCI 4
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.Os
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.Sh NAME
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.Nm pci
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.Nd generic PCI driver
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.Nd generic PCI bus driver
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.Sh SYNOPSIS
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To compile the PCI bus driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd device pci
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.Ed
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.Pp
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To compile in support for Single Root I/O Virtualization
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.Pq SR-IOV :
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.Bd -ragged -offset indent
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.Cd options PCI_IOV
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.Ed
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.Pp
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To compile in support for native PCI-express HotPlug:
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.Bd -ragged -offset indent
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.Cd options PCI_HP
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides a way for userland programs to read and write
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driver provides support for
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.Tn PCI
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devices in the kernel and limited access to
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.Tn PCI
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devices for userland.
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.Pp
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The
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.Nm
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driver provides a
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.Pa /dev/pci
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character device that can be used by userland programs to read and write
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.Tn PCI
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configuration registers.
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It also provides a way for userland programs to get a list of all
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Programs can also use this device to get a list of all
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.Tn PCI
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devices, or all
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.Tn PCI
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@ -73,14 +99,13 @@ children when
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.Tn PCI
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client drivers are dynamically
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loaded at runtime.
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.Sh KERNEL CONFIGURATION
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The
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.Nm
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device is included in the kernel as described in the SYNOPSIS section.
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The
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.Nm
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driver cannot be built as a
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.Xr kld 4 .
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driver also includes support for PCI-PCI bridges,
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various platform-specific Host-PCI bridges,
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and basic support for
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.Tn PCI
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VGA adapters.
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.Sh IOCTLS
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The following
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.Xr ioctl 2
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@ -309,6 +334,164 @@ reading registers, above, also apply to writing
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.Tn PCI
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configuration registers.
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.El
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.Sh LOADER TUNABLES
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Tunables can be set at the
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.Xr loader 8
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prompt before booting the kernel, or stored in
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.Xr loader.conf 5 .
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The current value of these tunables can be examined at runtime via
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.Xr sysctl 8
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nodes of the same name.
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Unless otherwise specified,
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each of these tunables is a boolean that can be enabled by setting the
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tunable to a non-zero value.
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.Bl -tag -width indent
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.It Va hw.pci.clear_bars Pq Defaults to 0
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Ignore any firmware-assigned memory and I/O port resources.
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This forces the
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.Tn PCI
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bus driver to allocate resource ranges for memory and I/O port resources
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from scratch.
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.It Va hw.pci.clear_buses Pq Defaults to 0
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Ignore any firmware-assigned bus number registers in PCI-PCI bridges.
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This forces the
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.Tn PCI
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bus driver and PCI-PCI bridge driver to allocate bus numbers for secondary
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buses behind PCI-PCI bridges.
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.It Va hw.pci.clear_pcib Pq Defaults to 0
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Ignore any firmware-assigned memory and I/O port resource windows in PCI-PCI
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bridges.
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This forces the PCI-PCI bridge driver to allocate memory and I/O port resources
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for resource windows from scratch.
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.Pp
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By default the PCI-PCI bridge driver will allocate windows that
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contain the firmware-assigned resources devices behind the bridge.
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In addition, the PCI-PCI bridge driver will suballocate from existing window
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regions when possible to satisfy a resource request.
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As a result,
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both
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.Va hw.pci.clear_bars
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and
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.Va hw.pci.clear_pcib
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must be enabled to fully ignore firmware-supplied resource assignments.
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.It Va hw.pci.default_vgapci_unit Pq Defaults to -1
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By default,
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the first
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.Tn PCI
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VGA adapter encountered by the system is assumed to be the boot display device.
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This tunable can be set to choose a specific VGA adapter by specifying the
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unit number of the associated
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.Va vgapci Ns Ar X
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device.
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.It Va hw.pci.do_power_nodriver Pq Defaults to 0
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Place devices into a low power state
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.Pq D3
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when a suitable device driver is not found.
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Can be set to one of the following values:
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.Bl -tag -width indent
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.It 3
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Powers down all
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.Tn PCI
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devices without a device driver.
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.It 2
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Powers down most devices without a device driver.
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PCI devices with the display, memory, and base peripheral device classes
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are not powered down.
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.It 1
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Similar to a setting of 2 except that storage controllers are also not
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powered down.
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.It 0
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All devices are left fully powered.
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.El
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.Pp
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A
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.Tn PCI
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device must support power management to be powered down.
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Placing a device into a low power state may not reduce power consumption.
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.It Va hw.pci.do_power_resume Pq Defaults to 1
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Place
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.Tn PCI
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devices into the fully powered state when resuming either the system or an
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individual device.
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Setting this to zero is discouraged as the system will not attempt to power
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up non-powered PCI devices after a suspend.
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.It Va hw.pci.do_power_suspend Pq Defaults to 1
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Place
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.Tn PCI
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devices into a low power state when suspending either the system or individual
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devices.
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Normally the D3 state is used as the low power state,
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but firmware may override the desired power state during a system suspend.
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.It Va hw.pci.enable_ari Pq Defaults to 1
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Enable support for PCI-express Alternative RID Interpretation.
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This is often used in conjunction with SR-IOV.
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.It Va hw.pci.enable_io_modes Pq Defaults to 1
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Enable memory or I/O port decoding in a PCI device's command register if it has
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firmware-assigned memory or I/O port resources.
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The firmware
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.Pq BIOS
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in some systems does not enable memory or I/O port decoding for some devices
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even when it has assigned resources to the device.
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This enables decoding for such resources during bus probe.
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.It Va hw.pci.enable_msi Pq Defaults to 1
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Enable support for Message Signalled Interrupts
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.Pq MSI .
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MSI interrupts can be disabled by setting this tunable to 0.
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.It Va hw.pci.enable_msix Pq Defaults to 1
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Enable support for extended Message Signalled Interrupts
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.Pq MSI-X .
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MSI-X interrupts can be disabled by setting this tunable to 0.
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.It Va hw.pci.enable_pcie_hp Pq Defaults to 1
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Enable support for native PCI-express HotPlug.
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.It Va hw.pci.honor_msi_blacklist Pq Defaults to 1
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MSI and MSI-X interrupts are disabled for certain chipsets known to have
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broken MSI and MSI-X implementations when this tunable is set.
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It can be set to zero to permit use of MSI and MSI-X interrupts if the
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chipset match is a false positive.
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.It Va hw.pci.iov_max_config Pq Defaults to 1MB
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The maximum amount of memory permitted for the configuration parameters
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used when creating Virtual Functions via SR-IOV.
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This tunable can also be changed at runtime via
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.Xr sysctl 8 .
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.It Va hw.pci.realloc_bars Pq Defaults to 0
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Attempt to allocate a new resource range during the initial device scan
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for any memory or I/O port resources with firmware-assigned ranges that
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conflict with another active resource.
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.It Va hw.pci.usb_early_takeover Pq Defaults to 1 on Tn amd64 and Tn i386
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Disable legacy device emulation of USB devices during the initial device
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scan.
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Set this tunable to zero to use USB devices via legacy emulation when
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using a custom kernel without USB controller drivers.
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.It Va hw.pci<D>.<B>.<S>.INT<P>.irq
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These tunables can be used to override the interrupt routing for legacy
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PCI INTx interrupts.
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Unlike other tunables in this list,
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these do not have corresponding sysctl nodes.
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The tunable name includes the address of the PCI device as well as the
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pin of the desired INTx IRQ to override:
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.Bl -tag -width indent
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.It <D>
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The domain
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.Pq or segment
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of the PCI device in decimal.
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.It <B>
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The bus address of the PCI device in decimal.
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.It <S>
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The slot of the PCI device in decimal.
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.It <P>
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The interrupt pin of the PCI slot to override.
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One of
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.Ql A ,
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.Ql B ,
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.Ql C ,
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or
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.Ql D .
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.El
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.Pp
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The value of the tunable is the raw IRQ value to use for the INTx interrupt
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pin identified by the tunable name.
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Mapping of IRQ values to platform interrupt sources is machine dependent.
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.El
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.Sh FILES
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.Bl -tag -width /dev/pci -compact
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.It Pa /dev/pci
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