The current implementation of lazy interrupts handling has some
issues that this tries to address.

We don't do the various workarounds we need to do when re-enabling
interrupts in some cases such as when returning from an interrupt
and thus we may still lose or get delayed decrementer or doorbell
interrupts.

The current scheme also makes it much harder to handle the external
"edge" interrupts provided by some BookE processors when using the
EPR facility (External Proxy) and the Freescale Hypervisor.

Additionally, we tend to keep interrupts hard disabled in a number
of cases, such as decrementer interrupts, external interrupts, or
when a masked decrementer interrupt is pending. This is sub-optimal.

This is an attempt at fixing it all in one go by reworking the way
we do the lazy interrupt disabling from the ground up.

The base idea is to replace the "hard_enabled" field with a
"irq_happened" field in which we store a bit mask of what interrupt
occurred while soft-disabled.

When re-enabling, either via arch_local_irq_restore() or when returning
from an interrupt, we can now decide what to do by testing bits in that
field.

We then implement replaying of the missed interrupts either by
re-using the existing exception frame (in exception exit case) or via
the creation of a new one from an assembly trampoline (in the
arch_local_irq_enable case).

This removes the need to play with the decrementer to try to create
fake interrupts, among others.

In addition, this adds a few refinements:

 - We no longer  hard disable decrementer interrupts that occur
while soft-disabled. We now simply bump the decrementer back to max
(on BookS) or leave it stopped (on BookE) and continue with hard interrupts
enabled, which means that we'll potentially get better sample quality from
performance monitor interrupts.

 - Timer, decrementer and doorbell interrupts now hard-enable
shortly after removing the source of the interrupt, which means
they no longer run entirely hard disabled. Again, this will improve
perf sample quality.

 - On Book3E 64-bit, we now make the performance monitor interrupt
act as an NMI like Book3S (the necessary C code for that to work
appear to already be present in the FSL perf code, notably calling
nmi_enter instead of irq_enter). (This also fixes a bug where BookE
perfmon interrupts could clobber r14 ... oops)

 - We could make "masked" decrementer interrupts act as NMIs when doing
timer-based perf sampling to improve the sample quality.

Signed-off-by-yet: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

v2:

- Add hard-enable to decrementer, timer and doorbells
- Fix CR clobber in masked irq handling on BookE
- Make embedded perf interrupt act as an NMI
- Add a PACA_HAPPENED_EE_EDGE for use by FSL if they want
  to retrigger an interrupt without preventing hard-enable

v3:

 - Fix or vs. ori bug on Book3E
 - Fix enabling of interrupts for some exceptions on Book3E

v4:

 - Fix resend of doorbells on return from interrupt on Book3E

v5:

 - Rebased on top of my latest series, which involves some significant
rework of some aspects of the patch.

v6:
 - 32-bit compile fix
 - more compile fixes with various .config combos
 - factor out the asm code to soft-disable interrupts
 - remove the C wrapper around preempt_schedule_irq

v7:
 - Fix a bug with hard irq state tracking on native power7

With the original EEH implementation, the access to config space of
the corresponding PCI device is done by RTAS sensitive function. That
depends on pci_dn heavily. That would limit EEH extension to other
platforms like powernv because other platforms might have different
ways to access PCI config space.

The patch splits those functions used to access PCI config space
and implement them in platform related EEH component. It would be
helpful to support EEH on multiple platforms simutaneously in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

With the original EEH implementation, the EEH global statistics
are maintained by individual global variables. That makes the
code a little hard to maintain.

The patch introduces extra struct eeh_stats for the EEH global
statistics so that it can be maintained in collective fashion.

It's the rework on the corresponding v5 patch. According to
the comments from David Laight, the EEH global statistics have
been changed for a litte bit so that they have fixed-type of
"u64". Also, the format used to print them has been changed to
"%llu" based on David's suggestion. Also, the output format of
EEH global statistics should be kept as intacted according to
Michael's suggestion that there might be tools parsing them.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The pci_dn has been replaced with eeh_dev. In order to comply with
the rule, the EEH platform implementation on pSeries should also
be adjusted for a little bit so that it will depend on eeh_dev instead
of pci_dn.

The patch replaces pci_dn with eeh_dev. The corresponding information
will be retrieved from eeh_dev instead of pci_dn.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The original EEH implementation is heavily depending on struct pci_dn.
We have to put EEH related information to pci_dn. Actually, we could
split struct pci_dn so that the EEH sensitive information to form an
individual struct, then EEH looks more independent.

The patch replaces pci_dn with eeh_dev for EEH aux components like
event and driver. Also, the eeh_event struct has been adjusted for
a little bit since eeh_dev has linked the associated FDT (Flat Device
Tree) node and PCI device. It's not necessary for eeh_event struct to
trace FDT node and PCI device. We can just simply to trace eeh_dev in
eeh_event.

The patch also renames function pcid_name() to eeh_pcid_name(), which
should be missed in the previous patch where the EEH aux components
have been cleaned up.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The original EEH implementation is heavily depending on struct pci_dn.
We have to put EEH related information to pci_dn. Actually, we could
split struct pci_dn so that the EEH sensitive information to form an
individual struct, then EEH looks more independent.

The patch replaces pci_dn with eeh_dev for EEH core.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

With original EEH implementation, struct pci_dn is used while building
PCI I/O address cache, which helps on searching the corresponding
PCI device according to the given physical I/O address. Besides, pci_dn
is associated with the corresponding PCI device while building its
I/O cache.

The patch replaces struct pci_dn with struct eeh_dev so that EEH address
cache won't depend on struct pci_dn. That will help EEH to become an
independent module in future. Besides, the binding of eeh_dev and PCI
device is done while building PCI device I/O cache.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

With original EEH implementation, all EEH related statistics have
been put into struct pci_dn. We've introduced struct eeh_dev to
replace struct pci_dn in EEH core components, including EEH sysfs
component.

The patch shows EEH statistics from struct eeh_dev instead of struct
pci_dn in EEH sysfs component. Besides, it also fixed the EEH device
retrieval from PCI device, which was introduced by the previous patch
in the series of patch.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Original EEH implementation depends on struct pci_dn heavily. However,
EEH shouldn't depend on that actually because EEH needn't share much
information with other PCI components. That's to say, EEH should have
worked independently.

The patch introduces struct eeh_dev so that EEH core components needn't
be working based on struct pci_dn in future. Also, struct pci_dn, struct
eeh_dev instances are created in dynamic fasion and the binding with EEH
device, OF node, PCI device is implemented as well.

The EEH devices are created after PHBs are detected and initialized, but
PCI emunation hasn't started yet. Apart from that, PHB might be created
dynamically through DLPAR component and the EEH devices should be creatd
as well. Another case might be OF node is created dynamically by DR
(Dynamic Reconfiguration), which has been defined by PAPR. For those OF
nodes created by DR, EEH devices should be also created accordingly. The
binding between EEH device and OF node is done while the EEH device is
initially created.

The binding between EEH device and PCI device should be done after PCI
emunation is done. Besides, PCI hotplug also needs the binding so that
the EEH devices could be traced from the newly coming PCI buses or PCI
devices.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The patch does some cleanup on the function names of EEH
aux components. Currently, only couple of function names from
eeh_cache have been adjusted so that:

        * The function name has prefix "eeh_addr_cache".
        * Move around pci_addr_cache_build() in the header file
          to reflect function call sequence.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

There're several EEH aux components and the patch does some cleanup
for them so that they look more clean.

        * Duplicated comments have been removed from the header file.
        * Comments have been reorganized so that it looks more clean.
        * The leading comments of functions are adjusted for a little
          bit so that the result of "make pdfdocs" would be more
          unified.
        * Function calls "xxx ()" has been replaced by "xxx()".
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

In order to enable particular PCI device, which has been included
in the parent PE. The involved PCI bridges should be enabled explicitly
if there has. On pSeries platform, there're dedicated RTAS calls
to fulfil the purpose.

The patch implements the function of configuring PCI bridges through
the dedicated RTAS calls. Besides, the function has been abstracted
by struct eeh_ops::configure_bridge so that the EEH core components
could support multiple platforms in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On RTAS compliant pSeries platform, one dedicated RTAS call has
been introduced to retrieve EEH temporary or permanent error log.

The patch implements the function of retriving EEH error log through
RTAS call. Besides, it has been abstracted by struct eeh_ops::get_log
so that EEH core components could support multiple platforms in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On RTAS compliant pSeries platform, there is a dedicated RTAS call
(ibm,set-slot-reset) to reset the specified PE. Furthermore, two
types of resets are supported: hot and fundamental. the type of
reset is to be used actually depends on the included PCI device's
requirements.

The patch implements resetting PE on pSeries platform through RTAS
call. Besides, it has been abstracted through struct eeh_ops::reset
so that EEH core components could support multiple platforms in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On pSeries platform, the PE state might be temporarily unavailable.
In that case, the firmware will return the corresponding wait time.
That means the kernel has to wait for appropriate time in order to
get the PE state.

The patch does the implementation for that. Besides, the function
has been abstracted through struct eeh_ops::wait_state so that EEH core
components could support multiple platforms in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On pSeries platform, there're 2 dedicated RTAS calls introduced to
retrieve the corresponding PE's state: ibm,read-slot-reset-state and
ibm,read-slot-reset-state2.

The patch implements the retrieval of PE's state according to the
given PE address. Besides, the implementation has been abstracted by
struct eeh_ops::get_state so that EEH core components could support
multiple platforms in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

There're 2 types of addresses used for EEH operations. The first
one would be BDF (Bus/Device/Function) address which is retrieved
from the reg property of the corresponding FDT node. Another one
is PE address that should be enquired from firmware through RTAS
call on pSeries platform. When issuing EEH operation, the PE address
has precedence over BDF address.

The patch implements retrieving PE address according to the given
BDF address on pSeries platform. Also, the struct eeh_early_enable_info
has been removed since the information can be figured out from
dn->pdn->phb->buid directly and that simplifies the code.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

There're 4 EEH operations that are covered by the dedicated RTAS
call <ibm,set-eeh-option>: enable or disable EEH, enable MMIO and
enable DMA. At early stage of system boot, the EEH would be tried
to enable on PCI device related device node. MMIO and DMA for
particular PE should be enabled when doing recovery on EEH errors
so that the PE could function properly again.

The patch implements it and abstract that through struct
eeh_ops::set_eeh. It would be help for EEH to support multiple
platforms in future.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The platform specific EEH operations have been abstracted by
struct eeh_ops. The individual platroms, including pSeries, needs
doing necessary initialization before the platform dependent EEH
operations work properly.

The patch is addressing that and do necessary platform initialization
for pSeries platform. More specificly, it will figure out the tokens
of EEH related RTAS calls.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

EEH has been implemented on RTAS-compliant pSeries platform.
That's to say, the EEH operations will be implemented through RTAS
calls eventually. The situation limited feasible extension on EEH.
In order to support EEH on multiple platforms like pseries and powernv
simutaneously. We have to split the platform dependent EEH options
up out of current implementation.

The patch addresses supporting EEH on multiple platforms. The pseries
platform dependent EEH operations will be abstracted by struct eeh_ops.
EEH core components will be built based on the registered EEH operations.
With the mechanism, what the individual platform needs to do is implement
platform dependent EEH operations.

For now, the pseries platform is covered under the mechanism. That means
we have to think about other platforms to support EEH, like powernv.
Besides, we only have framework for the mechanism and we have to implement
it for pseries platform later.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The EEH has been implemented on pSeries platform. The original
code looks a little bit nasty. The patch does cleanup on the
current EEH implementation so that it looks more clean.

        * Try adding prefix "eeh" for functions.
        * Some function names have been adjusted so that they looks
          shorter and meaningful.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The EEH has been implemented on pSeries platform. The original
code looks a little bit nasty. The patch does cleanup on the
current EEH implementation so that it looks more clean.

        * Duplicated comments have been removed from the corresponding
          header files.
        * Comments have been reorganized so that it looks more clean.
        * The leading comments of functions are adjusted for a little
          bit so that the result of "make pdfdocs" would be more
          unified.
        * Function definitions and calls have unified format as "xxx()".
          That means the format "xxx ()" has been replaced by "xxx()".
        * There're multiple functions implemented for resetting PE. The
          position of those functions have been move around so that they
          are adjacent to each other to reflect their relationship.
Signed-off-by: NGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On 64-bit, the mfmsr instruction can be quite slow, slower
than loading a field from the cache-hot PACA, which happens
to already contain the value we want in most cases.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

We were using CR0.EQ after EXCEPTION_COMMON, hoping it still
contained whether we came from userspace or kernel space.

However, under some circumstances, EXCEPTION_COMMON will
call C code and clobber non-volatile registers, so we really
need to re-load the previous MSR from the stackframe and
re-test.

While there, invert the condition to make the fast path more
obvious and remove the BUG_OPCODE which was a debugging
leftover and call .ret_from_except as we should.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

When running under a hypervisor that supports stolen time accounting,
we may call C code from the macro EXCEPTION_PROLOG_COMMON in the
exception entry path, which clobbers CR0.

However, the FPU and vector traps rely on CR0 indicating whether we
are coming from userspace or kernel to decide what to do.

So we need to restore that value after the C call
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Also use local_paca instead of get_paca() to avoid getting into
the smp_processor_id() debugging code from the debugger
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Other architectures such as x86 and ARM have been growing
new support for features like retrying page faults after
dropping the mm semaphore to break contention, or being
able to return from a stuck page fault when a SIGKILL is
pending.

This refactors our implementation of do_page_fault() to
move the error handling out of line in a way similar to
x86 and adds support for those two features.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

If we get a floating point, altivec or vsx unavaible interrupt in
kernel, we trigger a kernel error. There is no point preserving
the interrupt state, in fact, that can even make debugging harder
as the processor state might change (we may even preempt) between
taking the exception and landing in a debugger.

So just make those 3 disable interrupts unconditionally.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
---

v2: On BookE only disable when hitting the kernel unavailable
    path, otherwise it will fail to restore softe as
    fast_exception_return doesn't do it.

We currently turn interrupts back to their previous state before
calling do_page_fault(). This can be annoying when debugging as
a bad fault will potentially have lost some processor state before
getting into the debugger.

We also end up calling some generic code with interrupts enabled
such as notify_page_fault() with interrupts enabled, which could
be unexpected.

This changes our code to behave more like other architectures,
and make the assembly entry code call into do_page_faults() with
interrupts disabled. They are conditionally re-enabled from
within do_page_fault() in the same spot x86 does it.

While there, add the might_sleep() test in the case of a successful
trylock of the mmap semaphore, again like x86.

Also fix a bug in the existing assembly where r12 (_MSR) could get
clobbered by C calls (the DTL accounting in the exception common
macro and DISABLE_INTS) in some cases.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
---

v2. Add the r12 clobber fix

Some exceptions would unconditionally disable interrupts on entry,
which is fine, but calling lockdep every time not only adds more
overhead than strictly needed, but also means we get quite a few
"redudant" disable logged, which makes it hard to spot the really
bad ones.

So instead, split the macro used by the exception code into a
normal one and a separate one used when CONFIG_TRACE_IRQFLAGS is
enabled, and make the later skip th tracing if interrupts were
already disabled.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

We unconditionally hard enable interrupts. This is unnecessary as
syscalls are expected to always be called with interrupts enabled.

While at it, we add a WARN_ON if that is not the case and
CONFIG_TRACE_IRQFLAGS is enabled (we don't want to add overhead
to the fast path when this is not set though).

Thus let's remove the enabling (and associated irq tracing) from
the syscall entry path. Also on Book3S, replace a few mfmsr
instructions with loads of PACAMSR from the PACA, which should be
faster & schedule better.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This moves the inlines into system.h and changes the runlatch
code to use the thread local flags (non-atomic) rather than
the TIF flags (atomic) to keep track of the latch state.

The code to turn it back on in an asynchronous interrupt is
now simplified and partially inlined.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The perfmon interrupt is the sole user of a special variant of the
interrupt prolog which differs from the one used by external and timer
interrupts in that it saves the non-volatile GPRs and doesn't turn the
runlatch on.

The former is unnecessary and the later is arguably incorrect, so
let's clean that up by using the same prolog. While at it we rename
that prolog to use the _ASYNC prefix.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This removes the various bits of assembly in the kernel entry,
exception handling and SLB management code that were specific
to running under the legacy iSeries hypervisor which is no
longer supported.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This cleans up vio.c after the removal of the legacy iSeries platform.
It also removes some no longer referenced include files.
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The PowerPC legacy iSeries plateform is being removed along with the
"one looney iseries driver", so this code can now be removed as well.

cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The PowerPC legacy iSeries platform is being removed so this is no
longer selectable.

Cc: Alan Cox <alan@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The PowerPC legacy iSeries platform is being removed, so this code is no
longer needed.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The PowerPC legacy iSeries platform is being removed and this code is
no longer selectable.  There is more clean up that can be done, but this
just gets the old code out of the way.

Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Brian King <brking@linux.vnet.ibm.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>