* Extend the recovery from MCE in kernel space also to processes which

encounter an MCE in kernel space but while copying from user memory by
sending them a SIGBUS on return to user space and umapping the faulty
memory, by Tony Luck and Youquan Song.

* memcpy_mcsafe() rework by splitting the functionality into
copy_mc_to_user() and copy_mc_to_kernel(). This, as a result, enables
support for new hardware which can recover from a machine check
encountered during a fast string copy and makes that the default and
lets the older hardware which does not support that advance recovery,
opt in to use the old, fragile, slow variant, by Dan Williams.

* New AMD hw enablement, by Yazen Ghannam and Akshay Gupta.

* Do not use MSR-tracing accessors in #MC context and flag any fault
while accessing MCA architectural MSRs as an architectural violation
with the hope that such hw/fw misdesigns are caught early during the hw
eval phase and they don't make it into production.

* Misc fixes, improvements and cleanups, as always.
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