Jordan Niethe 130a8874f8 powerpc/64: Set up a kernel stack for secondaries before cpu_restore() ... [ Upstream commit 3c0b976bf20d236c57adcefa80f86a0a1d737727 ] Currently in generic_secondary_smp_init(), cur_cpu_spec->cpu_restore() is called before a stack has been set up in r1. This was previously fine as the cpu_restore() functions were implemented in assembly and did not use a stack. However commit 5a61ef74f2 ("powerpc/64s: Support new device tree binding for discovering CPU features") used __restore_cpu_cpufeatures() as the cpu_restore() function for a device-tree features based cputable entry. This is a C function and hence uses a stack in r1. generic_secondary_smp_init() is entered on the secondary cpus via the primary cpu using the OPAL call opal_start_cpu(). In OPAL, each hardware thread has its own stack. The OPAL call is ran in the primary's hardware thread. During the call, a job is scheduled on a secondary cpu that will start executing at the address of generic_secondary_smp_init(). Hence the value that will be left in r1 when the secondary cpu enters the kernel is part of that secondary cpu's individual OPAL stack. This means that __restore_cpu_cpufeatures() will write to that OPAL stack. This is not horribly bad as each hardware thread has its own stack and the call that enters the kernel from OPAL never returns, but it is still wrong and should be corrected. Create the temp kernel stack before calling cpu_restore(). As noted by mpe, for a kexec boot, the secondary CPUs are released from the spin loop at address 0x60 by smp_release_cpus() and then jump to generic_secondary_smp_init(). The call to smp_release_cpus() is in setup_arch(), and it comes before the call to emergency_stack_init(). emergency_stack_init() allocates an emergency stack in the PACA for each CPU. This address in the PACA is what is used to set up the temp kernel stack in generic_secondary_smp_init(). Move releasing the secondary CPUs to after the PACAs have been allocated an emergency stack, otherwise the PACA stack pointer will contain garbage and hence the temp kernel stack created from it will be broken. Fixes: 5a61ef74f2 ("powerpc/64s: Support new device tree binding for discovering CPU features") Signed-off-by: Jordan Niethe <jniethe5@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201014072837.24539-1-jniethe5@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-12-30 11:53:01 +01:00
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boot
configs
crypto
include	powerpc fixes for 5.10 #5	2020-12-05 11:16:21 -08:00
kernel	powerpc/64: Set up a kernel stack for secondaries before cpu_restore()	2020-12-30 11:53:01 +01:00
kexec
kvm
lib
math-emu
mm	powerpc fixes for 5.10 #6	2020-12-10 16:36:30 -08:00
net
oprofile
perf
platforms	A set of updates for the interrupt subsystem:	2020-12-06 11:15:55 -08:00
purgatory
sysdev
tools
xmon
Kbuild
Kconfig
Kconfig.debug
Makefile	Kbuild fixes for v5.10 (2nd)	2020-12-06 10:31:39 -08:00
Makefile.postlink