Truncate RAX to 32 bits, i.e. consume EAX, when retrieving the hypecall
index for a Xen hypercall. Per Xen documentation[*], the index is EAX
when the vCPU is not in 64-bit mode.
[*] http://xenbits.xenproject.org/docs/sphinx-unstable/guest-guide/x86/hypercall-abi.html
Fixes: 23200b7a30 ("KVM: x86/xen: intercept xen hypercalls if enabled")
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210422022128.3464144-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
6b48fd4cb2