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Do not disable bus mastering on outgoing preserved devices during
pci_device_shutdown() for kexec.
Preserved devices must be allowed to perform memory transactions during
a Live Update to ensure continuous operation. Clearing the bus
mastering bit would prevent these devices from issuing any memory
requests while the new kernel boots.
Because bridges upstream of preserved endpoint devices are also
automatically preserved, this change also avoids clearing bus mastering
on them. This is critical because clearing bus mastering on an upstream
bridge prevents the bridge from forwarding memory requests upstream (i.e.
it would prevent the endpoint device from accessing system RAM and doing
peer-to-peer transactions with devices not downstream of the bridge).
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://patch.msgid.link/20260918200640.887030-13-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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Freeze a device's outgoing preservation status (preserved or not
preserved) during shutdown. This enables the PCI core and drivers to
safely make decisions based on the device's preservation status during
shutdown.
Note that pci_liveupdate_freeze() is triggered by the PCI core rather
than from drivers participating in Live Update so that all devices can
have their status frozen (i.e. prevent non-preserved devices from
getting preserved late).
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://patch.msgid.link/20260918200640.887030-12-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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Adopt the ARI Forwarding Enable bit on preserved bridges and update
pci_dev->ari_enabled accordingly during a Live Update. This ensures that
the preserved devices on the bridge's secondary bus can be identified
with the same expanded 8-bit function number after a Live Update.
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://patch.msgid.link/20260918200640.887030-11-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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Adopt Access Control Services (ACS) controls on all incoming preserved
devices (endpoints and upstream bridges) during a Live Update.
Inheriting ACS flags avoids changing routing rules while memory
transactions are in flight from preserved devices. This is also strictly
necessary to ensure that IOMMU group assignments do not change during or
after Live Update.
The adopted controls are recorded by the pci_save_state() call in
pci_bus_add_device(), which runs before drivers bind, so they are
automatically reapplied by pci_restore_state() if the device is reset.
If that save buffer could not be allocated there is nowhere to record
the adopted controls, and they would be silently lost by the first
reset. Program ACS from scratch in that case, which is a better outcome
than leaving ACS disabled.
To simplify ACS inheritance, reject preserving any devices that require
quirks to enable ACS as those quirks would also have to take Live Update
into account.
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://patch.msgid.link/20260918200640.887030-10-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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Keep the secondary and subordinate bus numbers that the previous kernel
programmed into bridges, rather than assigning new ones, if the previous
kernel preserved any device across a Live Update. Do this even on
architectures that would otherwise always assign bus numbers themselves,
e.g. when pci=assign-busses is passed.
Preserved devices must be allowed to continue performing memory
transactions across a Live Update, so the kernel cannot change the
fabric topology. Changing the bus numbers of a bridge changes the
RequesterIDs of the devices below it, which would require disabling and
flushing any in-flight memory transactions first.
Apply the policy globally rather than only to the paths that contain
preserved devices. Bus numbers have to be preserved above a preserved
device anyway, since an upstream bridge cannot expand its window. A
global policy matches the scope of pcibios_assign_all_busses(), and
gives an answer that cannot change part way through the two passes of a
bridge scan.
Bridges that do not have bus numbers are still assigned new ones, so
hot-adding a bridge keeps working, both during and after a Live Update.
The two-pass bridge scan guarantees such bridges are only assigned bus
numbers above those already claimed by preserved bridges.
The exception is a bridge that was preserved but comes up without a
valid bus number configuration, e.g. because it was reset during kexec.
Refuse to assign it new bus numbers, since that would silently change
the BDF of every preserved device in its hierarchy. Also refuse to
assign bus numbers to the other bridges on the same bus, since the bus
numbers of the failed bridge can no longer be read from hardware and
handing them out would let an unrelated device inherit the BDF of a
preserved device.
Require that CONFIG_CARDBUS is not enabled to enable
CONFIG_PCI_LIVEUPDATE since preserving bus numbers on PCI-to-CardBus
bridges requires additional work but is not a priority at the moment.
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260918200640.887030-7-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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During PCI enumeration, the previous kernel might have passed state about
devices that were preserved across kexec. The PCI core needs to fetch
this state to identify which devices are "incoming" and require special
handling.
Add pci_liveupdate_setup_device() which is called during device setup
to fetch the serialized state (struct pci_ser) from the Live Update
Orchestrator. The first time this happens, pci_flb_retrieve() will run
and convert the array of pci_dev_ser structs into an xarray so that it
can be looked up efficiently.
If a device is found in the xarray, the PCI core stores a pointer to its
state in dev->liveupdate_incoming until pci_liveupdate_finish() is
called by the driver. This pointer allows the PCI core and drivers to
apply Live Update-specific logic to incoming devices in subsequent
commits.
Drivers can check if a device is an incoming preserved device (e.g.
during probe) by calling pci_liveupdate_is_incoming().
Note that any error during pci_flb_retrieve() must be treated as fatal.
The previous kernel handed off PCI devices that are performing DMA and
the current kernel cannot safely take over those devices without this
state.
CONFIG_64BIT is now required to enable CONFIG_PCI_LIVEUPDATE so that the
domain and bdf can be guaranteed to fit in an unsigned long and be used
as the xarray key.
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260918200640.887030-4-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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Add APIs to allow drivers to notify the PCI core of which devices are
being preserved across a Live Update for the next kernel, i.e.
"outgoing" devices.
Drivers must notify the PCI core when devices are preserved so that the
PCI core can update its FLB data (struct pci_ser) and track the list of
outgoing devices. pci_liveupdate_preserve() notifies the PCI core that a
device must be preserved across Live Update. pci_liveupdate_unpreserve()
reverses this (cancels the preservation of the device).
This tracking ensures the PCI core is fully aware of which devices may
need special handling during shutdown and kexec, and so the list of
preserved devices can be handed off to the next kernel.
For now, the API only supports preserving non-VF devices on a root bus
(not behind an PCI-to-PCI bridges).
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://patch.msgid.link/20260918200640.887030-3-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
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