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, 10 insertions, 0 deletions

diff --git a/platforms/mambo/mambo.c b/platforms/mambo/mambo.c
index 64248ef..bd151ed 100644
--- a/platforms/mambo/mambo.c
+++ b/platforms/mambo/mambo.c
@@ -92,6 +92,8 @@ static inline int callthru3(int command, unsigned long arg1, unsigned long arg2,
 #define BOGUS_DISK_WRITE	117
 #define BOGUS_DISK_INFO		118
 
+#define CALL_TCL		86
+
 static inline int callthru_disk_read(int id, void *buf, unsigned long sect,
 				     unsigned long nrsect)
 {
@@ -112,6 +114,14 @@ static inline unsigned long callthru_disk_info(int op, int id)
 			 (unsigned long)id);
 }
 
+extern unsigned long callthru_tcl(const char *str, int len);
+
+unsigned long callthru_tcl(const char *str, int len)
+{
+	prlog(PR_DEBUG, "Sending TCL to Mambo, cmd: %s\n", str);
+	return callthru2(CALL_TCL, (unsigned long)str, (unsigned long)len);
+}
+
 struct bogus_disk_info {
 	unsigned long size;
 	int id;