Fast reboot for P8

This is an experimental patch that implements "Fast reboot" on P8
machines.

The basic idea is that when the OS calls OPAL reboot, we gather all
the threads in the system using a combination of patching the reset
vector and soft-resetting them, then cleanup a few bits of hardware
(we do re-probe PCIe for example), and reload & restart the bootloader.

For Trusted Boot, this means we *add* measurements to the TPM, so you
will get *different* PCR values as compared to a full IPL. This makes
sense as if you want to be sure you are running something known then,
well, do a full IPL as soft reset should never be trusted to clear any
malicious code.

This is very experimental and needs a lot of testing and also auditing
code for other bits of HW that might need to be cleaned up.

BenH TODO: I also need to check if we are properly PERST'ing PCI devices.

This is partially based on old code I had to do that on P7. I only
support it on P8 though as there are issues with the PSI interrupts
on P7 that cannot be reliably solved.

Even though this should be considered somewhat experimental, we've had
a lot of success on a variety of machines. Dozens/hundreds of reboots
across Tuleta, Garrison and Habanero.

Currently, we've hidden it behind a NVRAM config option, which *is*
liable to change in the future (to ensure that only those who know
what they're doing enable it)

You can enable the experimental support via nvram option:
 nvram -p ibm,skiboot --update-config experimental-fast-reset=feeling-lucky

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[stewart@linux.vnet.ibm.com: hide behind nvram option, include Mambo fixes
from Mikey]
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/hw/slw.c b/hw/slw.c
index b916069..b4fb6ec 100644
--- a/hw/slw.c
+++ b/hw/slw.c
@@ -1060,6 +1060,8 @@ static void fast_sleep_enter(void)
 	}
 
 	primary_thread->save_l2_fir_action1 = tmp;
+	primary_thread->in_fast_sleep = true;
+
 	tmp = tmp & ~0x0200000000000000ULL;
 	rc = xscom_write(chip_id, XSCOM_ADDR_P8_EX(core, L2_FIR_ACTION1),
 			 tmp);
@@ -1082,7 +1084,7 @@ static void fast_sleep_enter(void)
 
 /* Workarounds while exiting fast-sleep */
 
-static void fast_sleep_exit(void)
+void fast_sleep_exit(void)
 {
 	uint32_t core = pir_to_core_id(this_cpu()->pir);
 	uint32_t chip_id = this_cpu()->chip_id;
@@ -1090,6 +1092,7 @@ static void fast_sleep_exit(void)
 	int rc;
 
 	primary_thread = this_cpu()->primary;
+	primary_thread->in_fast_sleep = false;
 
 	rc = xscom_write(chip_id, XSCOM_ADDR_P8_EX(core, L2_FIR_ACTION1),
 			primary_thread->save_l2_fir_action1);
@@ -1131,7 +1134,7 @@ static int64_t opal_config_cpu_idle_state(uint64_t state, uint64_t enter)
 opal_call(OPAL_CONFIG_CPU_IDLE_STATE, opal_config_cpu_idle_state, 2);
 
 #ifdef __HAVE_LIBPORE__
-static int64_t opal_slw_set_reg(uint64_t cpu_pir, uint64_t sprn, uint64_t val)
+int64_t opal_slw_set_reg(uint64_t cpu_pir, uint64_t sprn, uint64_t val)
 {
 
 	struct cpu_thread *c = find_cpu_by_pir(cpu_pir);