KVM: x86: Store gpa as gpa_t, not unsigned long, when unprotecting for retry

KVM: x86: Store gpa as gpa_t, not unsigned long, when unprotecting for retry

Store the gpa used to unprotect the faulting gfn for retry as a gpa_t, not
an unsigned long.  This fixes a bug where 32-bit KVM would unprotect and
retry the wrong gfn if the gpa had bits 63:32!=0.  In practice, this bug
is functionally benign, as unprotecting the wrong gfn is purely a
performance issue (thanks to the anti-infinite-loop logic).  And of course,
almost no one runs 32-bit KVM these days.

Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240831001538.336683-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>