From: Nathan Lynch <nathanl@xxxxxxxxxxxxx> [ Upstream commit ed2213bfb192ab51f09f12e9b49b5d482c6493f3 ] rtas_os_term() is called during panic. Its behavior depends on a couple of conditions in the /rtas node of the device tree, the traversal of which entails locking and local IRQ state changes. If the kernel panics while devtree_lock is held, rtas_os_term() as currently written could hang. Instead of discovering the relevant characteristics at panic time, cache them in file-static variables at boot. Note the lookup for "ibm,extended-os-term" is converted to of_property_read_bool() since it is a boolean property, not an RTAS function token. Signed-off-by: Nathan Lynch <nathanl@xxxxxxxxxxxxx> Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx> Reviewed-by: Andrew Donnellan <ajd@xxxxxxxxxxxxx> [mpe: Incorporate suggested change from Nick] Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20221118150751.469393-4-nathanl@xxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/powerpc/kernel/rtas.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index e847f9b1c5b9..6b5f49c9ad79 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -889,6 +889,7 @@ void __noreturn rtas_halt(void) /* Must be in the RMO region, so we place it here */ static char rtas_os_term_buf[2048]; +static s32 ibm_os_term_token = RTAS_UNKNOWN_SERVICE; void rtas_os_term(char *str) { @@ -900,14 +901,13 @@ void rtas_os_term(char *str) * this property may terminate the partition which we want to avoid * since it interferes with panic_timeout. */ - if (RTAS_UNKNOWN_SERVICE == rtas_token("ibm,os-term") || - RTAS_UNKNOWN_SERVICE == rtas_token("ibm,extended-os-term")) + if (ibm_os_term_token == RTAS_UNKNOWN_SERVICE) return; snprintf(rtas_os_term_buf, 2048, "OS panic: %s", str); do { - status = rtas_call(rtas_token("ibm,os-term"), 1, 1, NULL, + status = rtas_call(ibm_os_term_token, 1, 1, NULL, __pa(rtas_os_term_buf)); } while (rtas_busy_delay(status)); @@ -1277,6 +1277,13 @@ void __init rtas_initialize(void) no_entry = of_property_read_u32(rtas.dev, "linux,rtas-entry", &entry); rtas.entry = no_entry ? rtas.base : entry; + /* + * Discover these now to avoid device tree lookups in the + * panic path. + */ + if (of_property_read_bool(rtas.dev, "ibm,extended-os-term")) + ibm_os_term_token = rtas_token("ibm,os-term"); + /* If RTAS was found, allocate the RMO buffer for it and look for * the stop-self token if any */ -- 2.35.1
