linux-toradex.git/drivers/misc/cxl/main.c, branch v4.9.27

cxl: fix nested locking hang during EEH hotplug

2017-03-15T02:02:42+00:00

commit 171ed0fcd8966d82c45376f1434678e7b9d4d9b1 upstream.

Commit 14a3ae34bfd0 ("cxl: Prevent read/write to AFU config space while AFU
not configured") introduced a rwsem to fix an invalid memory access that
occurred when someone attempts to access the config space of an AFU on a
vPHB whilst the AFU is deconfigured, such as during EEH recovery.

It turns out that it's possible to run into a nested locking issue when EEH
recovery fails and a full device hotplug is required.
cxl_pci_error_detected() deconfigures the AFU, taking a writer lock on
configured_rwsem. When EEH recovery fails, the EEH code calls
pci_hp_remove_devices() to remove the device, which in turn calls
cxl_remove() -> cxl_pci_remove_afu() -> pci_deconfigure_afu(), which tries
to grab the writer lock that's already held.

Standard rwsem semantics don't express what we really want to do here and
don't allow for nested locking. Fix this by replacing the rwsem with an
atomic_t which we can control more finely. Allow the AFU to be locked
multiple times so long as there are no readers.

Fixes: 14a3ae34bfd0 ("cxl: Prevent read/write to AFU config space while AFU not configured")
Signed-off-by: Andrew Donnellan 
Acked-by: Frederic Barrat 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

cxl: Prevent read/write to AFU config space while AFU not configured

2017-03-15T02:02:42+00:00

commit 14a3ae34bfd0bcb1cc12d55b06a8584c11fac6fc upstream.

During EEH recovery, we deconfigure all AFUs whilst leaving the
corresponding vPHB and virtual PCI device in place.

If something attempts to interact with the AFU's PCI config space (e.g.
running lspci) after the AFU has been deconfigured and before it's
reconfigured, cxl_pcie_{read,write}_config() will read invalid values from
the deconfigured struct cxl_afu and proceed to Oops when they try to
dereference pointers that have been set to NULL during deconfiguration.

Add a rwsem to struct cxl_afu so we can prevent interaction with config
space while the AFU is deconfigured.

Reported-by: Pradipta Ghosh 
Suggested-by: Frederic Barrat 
Signed-off-by: Andrew Donnellan 
Signed-off-by: Vaibhav Jain 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

cxl: Prevent adapter reset if an active context exists

2016-10-19T09:35:39+00:00

This patch prevents resetting the cxl adapter via sysfs in presence of
one or more active cxl_context on it. This protects against an
unrecoverable error caused by PSL owning a dirty cache line even after
reset and host tries to touch the same cache line. In case a force reset
of the card is required irrespective of any active contexts, the int
value -1 can be stored in the 'reset' sysfs attribute of the card.

The patch introduces a new atomic_t member named contexts_num inside
struct cxl that holds the number of active context attached to the card
, which is checked against '0' before proceeding with the reset. To
prevent against a race condition where a context is activated just after
reset check is performed, the contexts_num is atomically set to '-1'
after reset-check to indicate that no more contexts can be activated on
the card anymore.

Before activating a context we atomically test if contexts_num is
non-negative and if so, increment its value by one. In case the value of
contexts_num is negative then it indicates that the card is about to be
reset and context activation is error-ed out at that point.

Fixes: 62fa19d4b4fd ("cxl: Add ability to reset the card")
Cc: stable@vger.kernel.org # v4.0+
Acked-by: Frederic Barrat 
Reviewed-by: Andrew Donnellan 
Signed-off-by: Vaibhav Jain 
Signed-off-by: Michael Ellerman

cxl: Add support for interrupts on the Mellanox CX4

2016-07-14T10:27:08+00:00

The Mellanox CX4 in cxl mode uses a hybrid interrupt model, where
interrupts are routed from the networking hardware to the XSL using the
MSIX table, and from there will be transformed back into an MSIX
interrupt using the cxl style interrupts (i.e. using IVTE entries and
ranges to map a PE and AFU interrupt number to an MSIX address).

We want to hide the implementation details of cxl interrupts as much as
possible. To this end, we use a special version of the MSI setup &
teardown routines in the PHB while in cxl mode to allocate the cxl
interrupts and configure the IVTE entries in the process element.

This function does not configure the MSIX table - the CX4 card uses a
custom format in that table and it would not be appropriate to fill that
out in generic code. The rest of the functionality is similar to the
"Full MSI-X mode" described in the CAIA, and this could be easily
extended to support other adapters that use that mode in the future.

The interrupts will be associated with the default context. If the
maximum number of interrupts per context has been limited (e.g. by the
mlx5 driver), it will automatically allocate additional kernel contexts
to associate extra interrupts as required. These contexts will be
started using the same WED that was used to start the default context.

Signed-off-by: Ian Munsie 
Reviewed-by: Andrew Donnellan 
Signed-off-by: Michael Ellerman

cxl: Add preliminary workaround for CX4 interrupt limitation

2016-07-14T10:27:02+00:00

The Mellanox CX4 has a hardware limitation where only 4 bits of the
AFU interrupt number can be passed to the XSL when sending an interrupt,
limiting it to only 15 interrupts per context (AFU interrupt number 0 is
invalid).

In order to overcome this, we will allocate additional contexts linked
to the default context as extra address space for the extra interrupts -
this will be implemented in the next patch.

This patch adds the preliminary support to allow this, by way of adding
a linked list in the context structure that we use to keep track of the
contexts dedicated to interrupts, and an API to simultaneously iterate
over the related context structures, AFU interrupt numbers and hardware
interrupt numbers. The point of using a single API to iterate these is
to hide some of the details of the iteration from external code, and to
reduce the number of APIs that need to be exported via base.c to allow
built in code to call.

Signed-off-by: Ian Munsie 
Reviewed-by: Frederic Barrat 
Reviewed-by: Andrew Donnellan 
Signed-off-by: Michael Ellerman

cxl: Allow a default context to be associated with an external pci_dev

2016-07-14T10:26:52+00:00

The cxl kernel API has a concept of a default context associated with
each PCI device under the virtual PHB. The Mellanox CX4 will also use
the cxl kernel API, but it does not use a virtual PHB - rather, the AFU
appears as a physical function as a peer to the networking functions.

In order to allow the kernel API to work with those networking
functions, we will need to associate a default context with them as
well. To this end, refactor the corresponding code to do this in vphb.c
and export it so that it can be called from the PHB code.

Signed-off-by: Ian Munsie 
Reviewed-by: Frederic Barrat 
Reviewed-by: Andrew Donnellan 
Signed-off-by: Michael Ellerman

cxl: Adapter failure handling

2016-03-09T12:40:00+00:00

Check the AFU state whenever an API is called. The hypervisor may
issue a reset of the adapter when it detects a fault. When it happens,
it launches an error recovery which will either move the AFU to a
permanent failure state, or in the disabled state.
If the AFU is found to be disabled, detach all existing contexts from
it before issuing a AFU reset to re-enable it.

Before detaching contexts, notify any kernel driver through the EEH
callbacks of the AFU pci device.

Co-authored-by: Frederic Barrat 
Signed-off-by: Frederic Barrat 
Signed-off-by: Christophe Lombard 
Reviewed-by: Manoj Kumar 
Acked-by: Ian Munsie 
Signed-off-by: Michael Ellerman

cxl: Add guest-specific code

2016-03-09T12:36:52+00:00

The new of.c file contains code to parse the device tree to find out
about cxl adapters and AFUs.

guest.c implements the guest-specific callbacks for the backend API.

The process element ID is not known until the context is attached, so
we have to separate the context ID assigned by the cxl driver from the
process element ID visible to the user applications. In bare-metal,
the 2 IDs match.

Co-authored-by: Frederic Barrat 
Signed-off-by: Frederic Barrat 
Signed-off-by: Christophe Lombard 
Reviewed-by: Manoj Kumar 
Acked-by: Ian Munsie 
[mpe: Fix SMP=n build, fix PSERIES=n build, minor whitespace fixes]
Signed-off-by: Michael Ellerman

cxl: Separate bare-metal fields in adapter and AFU data structures

2016-03-09T02:05:54+00:00

Introduce sub-structures containing the bare-metal specific fields in
the structures describing the adapter (struct cxl) and AFU (struct
cxl_afu).
Update all their references.

Co-authored-by: Frederic Barrat 
Signed-off-by: Frederic Barrat 
Signed-off-by: Christophe Lombard 
Reviewed-by: Manoj Kumar 
Acked-by: Ian Munsie 
Signed-off-by: Michael Ellerman

cxl: New hcalls to support cxl adapters

2016-03-09T02:05:52+00:00

The hypervisor calls provide an interface with a coherent platform
facility and function. It matches version 0.16 of the 'PAPR changes'
document.

The following hcalls are supported:
H_ATTACH_CA_PROCESS    Attach a process element to a coherent platform
                       function.
H_DETACH_CA_PROCESS    Detach a process element from a coherent
                       platform function.
H_CONTROL_CA_FUNCTION  Allow the partition to manipulate or query
                       certain coherent platform function behaviors.
H_COLLECT_CA_INT_INFO  Collect interrupt info about a coherent.
                       platform function after an interrupt occurred
H_CONTROL_CA_FAULTS    Control the operation of a coherent platform
                       function after a fault occurs.
H_DOWNLOAD_CA_FACILITY Support for downloading a base adapter image to
                       the coherent platform facility, and for
                       validating the entire image after the download.
H_CONTROL_CA_FACILITY  Allow the partition to manipulate or query
                       certain coherent platform facility behaviors.

Co-authored-by: Frederic Barrat 
Signed-off-by: Frederic Barrat 
Signed-off-by: Christophe Lombard 
Reviewed-by: Manoj Kumar 
Acked-by: Ian Munsie 
Signed-off-by: Michael Ellerman