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Consolidate the mux and demux of ipi messages into smp.c and call
a new smp_ops callback to actually trigger the ipi.
The powerpc architecture code is optimised for having 4 distinct
ipi triggers, which are mapped to 4 distinct messages (ipi many, ipi
single, scheduler ipi, and enter debugger). However, several interrupt
controllers only provide a single software triggered interrupt that
can be delivered to each cpu. To resolve this limitation, each smp_ops
implementation created a per-cpu variable that is manipulated with atomic
bitops. Since these lines will be contended they are optimialy marked as
shared_aligned and take a full cache line for each cpu. Distro kernels
may have 2 or 3 of these in their config, each taking per-cpu space
even though at most one will be in use.
This consolidation removes smp_message_recv and replaces the single call
actions cases with direct calls from the common message recognition loop.
The complicated debugger ipi case with its muxed crash handling code is
moved to debug_ipi_action which is now called from the demux code (instead
of the multi-message action calling smp_message_recv).
I put a call to reschedule_action to increase the likelyhood of correctly
merging the anticipated scheduler_ipi() hook coming from the scheduler
tree; that single required call can be inlined later.
The actual message decode is a copy of the old pseries xics code with its
memory barriers and cache line spacing, augmented with a per-cpu unsigned
long based on the book-e doorbell code. The optional data is set via a
callback from the implementation and is passed to the new cause-ipi hook
along with the logical cpu number. While currently only the doorbell
implemntation uses this data it should be almost zero cost to retrieve and
pass it -- it adds a single register load for the argument from the same
cache line to which we just completed a store and the register is dead
on return from the call. I extended the data element from unsigned int
to unsigned long in case some other code wanted to associate a pointer.
The doorbell check_self is replaced by a call to smp_muxed_ipi_resend,
conditioned on the CPU_DBELL feature. The ifdef guard could be relaxed
to CONFIG_SMP but I left it with BOOKE for now.
Also, the doorbell interrupt vector for book-e was not calling irq_enter
and irq_exit, which throws off cpu accounting and causes code to not
realize it is running in interrupt context. Add the missing calls.
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Now that smp_ops->smp_message_pass is always called with an (online) cpu
number for the target remove the checks for MSG_ALL and MSG_ALL_BUT_SELF.
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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If we are soft disabled and receive a doorbell exception we don't process
it immediately. This means we need to check on the way out of irq restore
if there are any doorbell exceptions to process.
The problem is at that point we don't know what our regs are, and that
in turn makes xmon unhappy. To workaround the problem, instead of checking
for and processing doorbells, we check for any doorbells and if there were
any we send ourselves another.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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include/asm-generic/irq_regs.h declares per-cpu irq_regs variables and
get_irq_regs() and set_irq_regs() helper functions to maintain them.
These can be used to access the proper pt_regs structure related to the
current interrupt entry (if any).
In the powerpc arch code, this is used to maintain irq regs on
decrementer and external interrupt exceptions. However, for the
doorbell exceptions used by the msgsnd/msgrcv IPI mechanism of newer
BookE CPUs, the irq_regs are not kept up to date.
In particular this means that xmon will not work properly on SMP,
because the secondary xmon instances started by IPI will blow up when
they cannot retrieve the irq regs.
This patch fixes the problem by adding calls to maintain the irq regs
across doorbell exceptions.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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The doorbells use the content of the PIR register to match messages
from other CPUs. This may or may not be the same as our linux CPU
number, so using that as the "target" is no right.
Instead, we sample the PIR register at boot on every processor
and use that value subsequently when sending IPIs.
We also use a per-cpu message mask rather than a global array which
should limit cache line contention.
Note: We could use the CPU number in the device-tree instead of
the PIR register, as they are supposed to be equivalent. This
might prove useful if doorbells are to be used to kick CPUs out
of FW at boot time, thus before we can sample the PIR. This is
however not the case now and using the PIR just works.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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... where it belongs
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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The e500mc supports the new msgsnd/doorbell mechanisms that were added in
the Power ISA 2.05 architecture. We use the normal level doorbell for
doing SMP IPIs at this point.
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Milton Miller
Michael Ellerman
David Gibson
Benjamin Herrenschmidt
Kumar Gala