Merge branch 'svm' of https://github.com/kvm-x86/linux into HEAD

Clean up SVM's enter/exit assembly code so that it can be compiled
without OBJECT_FILES_NON_STANDARD.  The "standard" __svm_vcpu_run() can't
be made 100% bulletproof, as RBP isn't restored on #VMEXIT, but that's
also the case for __vmx_vcpu_run(), and getting "close enough" is better
than not even trying.

As for SEV-ES, after yet another refresher on swap types, I realized
KVM can simply let the hardware restore registers after #VMEXIT, all
that's missing is storing the current values to the host save area
(they are swap type B).  This should provide 100% accuracy when using
stack frames for unwinding, and requires less assembly.

In between, build the SEV-ES code iff CONFIG_KVM_AMD_SEV=y, and yank out
"support" for 32-bit kernels in __svm_sev_es_vcpu_run, which was
unnecessarily polluting the code for a configuration that is disabled
at build time.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>