target/ppc: Build rtas error log upon an MCE

target/ppc: Build rtas error log upon an MCE

Upon a machine check exception (MCE) in a guest address space,
KVM causes a guest exit to enable QEMU to build and pass the
error to the guest in the PAPR defined rtas error log format.

This patch builds the rtas error log, copies it to the rtas_addr
and then invokes the guest registered machine check handler. The
handler in the guest takes suitable action(s) depending on the type
and criticality of the error. For example, if an error is
unrecoverable memory corruption in an application inside the
guest, then the guest kernel sends a SIGBUS to the application.
For recoverable errors, the guest performs recovery actions and
logs the error.

Signed-off-by: Aravinda Prasad <arawinda.p@gmail.com>
[Assume SLOF has allocated enough room for rtas error log]
Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20200130184423.20519-5-ganeshgr@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>