Commit 36350e00 authored by Mark Nelson's avatar Mark Nelson Committed by Benjamin Herrenschmidt

powerpc/pseries: Fix kexec regression caused by CPPR tracking

The code to track the CPPR values added by commit
49bd3647 ("powerpc/pseries: Track previous
CPPR values to correctly EOI interrupts") broke kexec on pseries because
the kexec code in xics.c calls xics_set_cpu_priority() before the IPI has
been EOI'ed. This wasn't a problem previously but it now triggers a BUG_ON
in xics_set_cpu_priority() because os_cppr->index isn't 0.

Fix this problem by setting the index on the CPPR stack to 0 before calling
xics_set_cpu_priority() in xics_teardown_cpu().

Also make it clear that we only want to set the priority when there's just
one CPPR value in the stack, and enforce it by updating the value of
os_cppr->stack[0] rather than os_cppr->stack[os_cppr->index].

While we're at it change the BUG_ON to a WARN_ON.
Reported-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarMark Nelson <markn@au1.ibm.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 1a45dcfe
...@@ -784,9 +784,13 @@ static void xics_set_cpu_priority(unsigned char cppr) ...@@ -784,9 +784,13 @@ static void xics_set_cpu_priority(unsigned char cppr)
{ {
struct xics_cppr *os_cppr = &__get_cpu_var(xics_cppr); struct xics_cppr *os_cppr = &__get_cpu_var(xics_cppr);
BUG_ON(os_cppr->index != 0); /*
* we only really want to set the priority when there's
* just one cppr value on the stack
*/
WARN_ON(os_cppr->index != 0);
os_cppr->stack[os_cppr->index] = cppr; os_cppr->stack[0] = cppr;
if (firmware_has_feature(FW_FEATURE_LPAR)) if (firmware_has_feature(FW_FEATURE_LPAR))
lpar_cppr_info(cppr); lpar_cppr_info(cppr);
...@@ -821,8 +825,14 @@ void xics_setup_cpu(void) ...@@ -821,8 +825,14 @@ void xics_setup_cpu(void)
void xics_teardown_cpu(void) void xics_teardown_cpu(void)
{ {
struct xics_cppr *os_cppr = &__get_cpu_var(xics_cppr);
int cpu = smp_processor_id(); int cpu = smp_processor_id();
/*
* we have to reset the cppr index to 0 because we're
* not going to return from the IPI
*/
os_cppr->index = 0;
xics_set_cpu_priority(0); xics_set_cpu_priority(0);
/* Clear any pending IPI request */ /* Clear any pending IPI request */
......
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