kexec: load-preserve-context option on s390

[Michael Holzheu]

Hello Vivec,

On Thu, 2011-09-29 at 09:32 -0400, Vivek Goyal wrote:
> On Thu, Sep 29, 2011 at 08:51:02AM +0900, Simon Horman wrote:
> > On Mon, Sep 26, 2011 at 03:09:09PM +0200, Michael Holzheu wrote:
> > > Hello Simon,
> > > 
> > > I think the --load-preserve-context and --load-jump-back-helper kexec
> > > options are not working on s390 because we do not support
> > > CONFIG_KEXEC_JUMP. I assume the same is true also on other
> > > architectures. Correct me, if I am wrong. Unfortunately I did not find
> > > much documentation for that feature.
> > > 
> > > Wouldn't it be better to print an error message when the options are
> > > used on those architectures?
> > 
> > Ideally it would be nice if kexec-tools could ask the kernel
> > if KEXEC_JUMP is supported (or enabled?) or not rather than
> > hardcoding this information into kexec-tools on a per-architecture basis.
> 
> Shouldn't kexec system call return error if KEXEC_JUMP is not supported
> and user asked for it?

I think currently not. I assume that we should check the
KEXEC_PRESERVE_CONTEXT flag in the kexec_load system call.

What about the following:
---
 kernel/kexec.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -949,6 +949,10 @@ SYSCALL_DEFINE4(kexec_load, unsigned lon
 	if (!capable(CAP_SYS_BOOT))
 		return -EPERM;
 
+#ifndef CONFIG_KEXEC_JUMP
+	if (flags & KEXEC_PRESERVE_CONTEXT)
+		return -EOPNOTSUPP;
+#endif
 	/*
 	 * Verify we have a legal set of flags
 	 * This leaves us room for future extensions.