KVM: arm64: Fix AArch32 DBGBXVR<n> handling

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Fix AArch32 DBGBXVR<n> handling The consolidation of the breakpoint and watchpoint register accessors switched DBGBXVR<n> from trap_bvr() to trap_dbg_wb_reg(). The latter selects backing storage with demux_wb_reg(), which only handles Op2 values 4 through 7. Since DBGBXVR<n> uses Op2 1, an AArch32 guest access hits KVM_BUG_ON() and marks the VM dead. DBGBXVR<n> aliases DBGBVR<n>_EL1[63:32], and its AA32(HI) descriptor already selects the upper half. Map Op2 1 to dbg_bvr[] alongside Op2 4, restoring the pre-regression behavior.

Where it's fixed