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/openbmc/linux/arch/powerpc/kernel/
H A Dhead_64.Sdiff 768d18ad6d5e600d911f9499ca287d6986d8d81b Tue May 10 14:28:37 CDT 2011 Milton Miller <miltonm@bga.com> powerpc: Don't search for paca in freed memory

Starting with 1426d5a3bd07589534286375998c0c8c6fdc5260 (powerpc:
Dynamically allocate pacas) we free the memory for pacas beyond
cpu_possible, but we failed to update the loop the secondary cpus use
to find their paca. If the system has running cpu threads for which
the kernel did not allocate a paca for they will search the memory that
was freed. For instance this could happen when the device tree for
a kdump kernel was not updated after a cpu hotplug, or the kernel is
running with more cpus than the kernel was configured.

Since c1854e00727f50f7ac99e98d26ece04c087ef785 (powerpc: Set nr_cpu_ids
early and use it to free PACAs) we set nr_cpu_ids before telling the
cpus to advance, so use that to limit the search.

We can't reference nr_cpu_ids without CONFIG_SMP because it is defined
as 1 instead of a memory location, but any extra threads should be sent
to kexec_wait in that case anyways, so make that explicit and remove
the search loop for UP.

Note to stable: The fix also requires
c1854e00727f50f7ac99e98d26ece04c087ef785 (powerpc: Set
nr_cpu_ids early and use it to free PACAs) to function. Also
9d07bc841c9779b4d7902e417f4e509996ce805d (Properly handshake CPUs going
out of boot spin loop) affects the second chunk, specifically the branch
target was 3b before and is 4b after that patch, and there was a blank
line before the #ifdef CONFIG_SMP that was removed

Cc: <stable@kernel.org> # .34.x: c1854e0072 powerpc: Set nr_cpu_ids early
Cc: <stable@kernel.org> # .34.x
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff 1426d5a3bd07589534286375998c0c8c6fdc5260 Thu Jan 28 07:23:22 CST 2010 Michael Ellerman <michael@ellerman.id.au> powerpc: Dynamically allocate pacas

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
H A Dpaca.cdiff 1426d5a3bd07589534286375998c0c8c6fdc5260 Thu Jan 28 07:23:22 CST 2010 Michael Ellerman <michael@ellerman.id.au> powerpc: Dynamically allocate pacas

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
H A Dprom.cdiff 1426d5a3bd07589534286375998c0c8c6fdc5260 Thu Jan 28 07:23:22 CST 2010 Michael Ellerman <michael@ellerman.id.au> powerpc: Dynamically allocate pacas

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
H A Dsetup-common.cdiff 1426d5a3bd07589534286375998c0c8c6fdc5260 Thu Jan 28 07:23:22 CST 2010 Michael Ellerman <michael@ellerman.id.au> powerpc: Dynamically allocate pacas

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
H A Dsetup_64.cdiff 1426d5a3bd07589534286375998c0c8c6fdc5260 Thu Jan 28 07:23:22 CST 2010 Michael Ellerman <michael@ellerman.id.au> powerpc: Dynamically allocate pacas

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
/openbmc/linux/arch/powerpc/include/asm/
H A Dpaca.hdiff 1426d5a3bd07589534286375998c0c8c6fdc5260 Thu Jan 28 07:23:22 CST 2010 Michael Ellerman <michael@ellerman.id.au> powerpc: Dynamically allocate pacas

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>