[PATCH v2] powerpc/powernv: Make possible for user to force a full ipl cec reboot

Ever since fast reboot is enabled by default in opal,
opal_cec_reboot() will use fast-reset instead of full IPL to perform
system reboot. This leaves the user with no direct way to force a full
IPL reboot except changing an nvram setting that persistently disables
fast-reset for all subsequent reboots.

This patch provides a more direct way for the user to force a one-shot
full IPL reboot by passing the command line argument 'full' to the
reboot command. So the user will be able to tweak the reboot behavior
via:

  $ sudo reboot full	# Force a full ipl reboot skipping fast-reset

  or
  $ sudo reboot  	# default reboot path (usually fast-reset)

The reboot command passes the un-parsed command argument to the kernel
via the 'Reboot' syscall which is then passed on to the arch function
pnv_restart(). The patch updates pnv_restart() to handle this cmd-arg
and issues opal_cec_reboot2 with OPAL_REBOOT_FULL_IPL to force a full
IPL reset.

Signed-off-by: Vaibhav Jain <redacted>
---
Change-log:

v2	-> Updated the code to handle case when opal_cec_reboot2() is
	   not supported by opal. [Andrew]

	-> Force a call to opal_cec_reboot() is opal_cec_reboot2()
           fails or the action verb 'cmd' is not recognized.
---
 arch/powerpc/include/asm/opal-api.h    |  1 +
 arch/powerpc/platforms/powernv/setup.c | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
index 8365353330b4..870fb7b239ea 100644
--- a/arch/powerpc/include/asm/opal-api.h
+++ b/arch/powerpc/include/asm/opal-api.h

@@ -1050,6 +1050,7 @@ enum OpalSysCooling {
 enum {
 	OPAL_REBOOT_NORMAL		= 0,
 	OPAL_REBOOT_PLATFORM_ERROR	= 1,
+	OPAL_REBOOT_FULL_IPL		= 2,
 };
 
 /* Argument to OPAL_PCI_TCE_KILL */

diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index adddde023622..650484e0940b 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c

@@ -224,7 +224,22 @@ static void  __noreturn pnv_restart(char *cmd)
 	pnv_prepare_going_down();
 
 	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
-		rc = opal_cec_reboot();
+		/* See if we need to do a full IPL reboot */
+		if (cmd && strcmp(cmd, "full") == 0)
+			rc = opal_cec_reboot2(OPAL_REBOOT_FULL_IPL, NULL);
+		else
+			rc = OPAL_UNSUPPORTED;
+
+		if (!(rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT)) {
+			if (cmd) {
+				pr_warn("Couldn't do a '%s' reboot. Err=%ld\n",
+					cmd, rc);
+				/* reset cmd to force a cec_reboot now */
+				cmd = NULL;
+			}
+			rc = opal_cec_reboot();
+		}
+
 		if (rc == OPAL_BUSY_EVENT)
 			opal_poll_events(NULL);
 		else

-- 
2.17.1

On 03/09/18 20:26, Vaibhav Jain wrote:

The logic here is a bit hard to follow, relying on if (cmd && strcmp...) 
failing then setting rc = OPAL_UNSUPPORTED in order to handle the normal 
case seems a bit backwards.

I think I would slightly prefer it if the !cmd case were handled first 
to make it clear that opal_cec_reboot() is the normal case.

But either way:

Acked-by: Andrew Donnellan <redacted>


-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited

Thanks for reviewing this patch Andrew,

Andrew Donnellan [off-list ref] writes:

The logic here is a bit hard to follow, relying on if (cmd && strcmp...) 
failing then setting rc = OPAL_UNSUPPORTED in order to handle the normal 
case seems a bit backwards.

Agree. With this change I am trying to make adding new reboot types in
future simpler, without resorting to major refactoring of the
function. opal_cec_reboot() should be a fallback for any failures in
doing a typed reboot. So adding a new foobar reboot type just needs
adding a new branch in the if-else ladder.

if (cmd && strcmp(cmd, "full") == 0)
    rc = opal_cec_reboot2(OPAL_REBOOT_FULL_IPL, NULL);
else if(cmd && strcmd(cmd, "foobar") == 0)
    rc = /* new code here */
else
    rc = OPAL_UNSUPPORTED;

I think I would slightly prefer it if the !cmd case were handled first 
to make it clear that opal_cec_reboot() is the normal case.

Fair suggestion. But then I will still have to handle the errors just
after the if-else ladder is finished to determine if I need to fallback.

Acked-by: Andrew Donnellan <redacted>

Thanks

-- 
Vaibhav Jain [off-list ref]
Linux Technology Center, IBM India Pvt. Ltd.

On 09/03/2018 03:56 PM, Vaibhav Jain wrote:

Ever since fast reboot is enabled by default in opal,
opal_cec_reboot() will use fast-reset instead of full IPL to perform
system reboot. This leaves the user with no direct way to force a full
IPL reboot except changing an nvram setting that persistently disables
fast-reset for all subsequent reboots.

This patch provides a more direct way for the user to force a one-shot
full IPL reboot by passing the command line argument 'full' to the
reboot command. So the user will be able to tweak the reboot behavior
via:

.../...

As discussed offline, please handle OPAL_SUCCESS case well.

-Vasant