[block] Provide abstraction to allow system to be quiesced
When performing a SAN boot via INT 13, there is no way for the
operating system to indicate that it has finished using the INT 13 SAN
device. We therefore have no opportunity to clean up state before the
loaded operating system's native drivers take over. This can cause
problems when booting Windows, which tends not to be forgiving of
unexpected system state.
Windows will typically write a flag to the SAN device as the last
action before transferring control to the native drivers. We can use
this as a heuristic to bring the system to a quiescent state (without
performing a full shutdown); this provides us an opportunity to
temporarily clean up state that could otherwise prevent a successful
Windows boot.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Describe all SAN devices via ACPI tables such as the iBFT. For tables
that can describe only a single device (i.e. the aBFT and sBFT), one
table is installed per device. For multi-device tables (i.e. the
iBFT), all devices are described in a single table.
An underlying SAN device connection may be closed at the time that we
need to construct an ACPI table. We therefore introduce the concept
of an "ACPI descriptor" which enables the SAN boot code to maintain an
opaque pointer to the underlying object, and an "ACPI model" which can
build tables from a list of such descriptors. This separates the
lifecycles of ACPI descriptions from the lifecycles of the block
device interfaces, and allows for construction of the ACPI tables even
if the block device interface has been closed.
For a multipath SAN device, iPXE will wait until sufficient
information is available to describe all devices but will not wait for
all paths to connect successfully. For example: with a multipath
iSCSI boot iPXE will wait until at least one path has become available
and name resolution has completed on all other paths. We do this
since the iBFT has to include IP addresses rather than DNS names. We
will commence booting without waiting for the inactive paths to either
become available or close; this avoids unnecessary boot delays.
Note that the Linux kernel will refuse to accept an iBFT with more
than two NIC or target structures. We therefore describe only the
NICs that are actually required in order to reach the described
targets. Any iBFT with at most two targets is therefore guaranteed to
describe at most two NICs.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
For some block device protocols, the active path may continue to
receive xfer_window_changed() notifications during normal use. These
currently result in the active path being erroneously closed.
Fix by ignoring any xfer_window_changed() messages if this path is
already the active path.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[block] Retry reopening indefinitely for multipath devices
For multipath SAN devices, verify that the device is capable of being
opened (i.e. that all URIs are parseable and that at least one path is
alive) and thereafter retry indefinitely to reopen the device as
needed.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[block] Add a small delay between attempts to reopen SAN targets
When all SAN targets are completely unreachable, there will be a
natural delay between reopening attempts due to the network connection
timeout on the unreachable targets.
However, some SAN targets may accept connections instantly and report
a temporary unavailability by e.g. failing the TEST UNIT READY
command. If all targets are behaving this way then there will be no
natural delay, and we will attempt to saturate the network with
connection attempts.
Fix by introducing a small delay between attempts.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow the SAN retry count to be configured via the ${san-retry}
setting, defaulting to the current value of 10 retries if not
specified.
Note that setting a retry count of zero is inadvisable, since iSCSI
targets in particular will often report spurious errors such as "power
on occurred" for the first few commands.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add basic support for multipath block devices. The "sanboot" and
"sanhook" commands now accept a list of SAN URIs. We open all URIs
concurrently. The first connection to become available for issuing
block device commands is marked as the active path and used for all
subsequent commands; all other connections are then closed. Whenever
the active path fails, we reopen all URIs and repeat the process.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The SCSI layer currently implements a retry loop in order to retry
commands that fail due to spurious "error" conditions such as "power
on occurred". Move this retry loop to the generic SAN device layer:
this allow for retries due to other transient error conditions such as
an iSCSI target having dropped the connection due to inactivity.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The concept of the SAN drive number is meaningful only in a BIOS
environment, where it represents the INT13 drive number (0x80 for the
first hard disk). We retain this concept in a UEFI environment to
allow for a simple way for iPXE commands to refer to SAN drives.
Centralise the concept of the default drive number, since it is shared
between all supported environments.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown