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MIPS: KVM: Handle TRAP exceptions from guest kernel

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Trap instructions are used by Linux to implement BUG_ON(), however KVM
doesn't pass trap exceptions on to the guest if they occur in guest
kernel mode, instead triggering an internal error "Exception Code: 13,
not yet handled". The guest kernel then doesn't get a chance to print
the usual BUG message and stack trace.

Implement handling of the trap exception so that it gets passed to the
guest and the user is left with a more useful log message.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
This commit is contained in:
James Hogan
2015-02-06 16:03:57 +00:00
parent 64bedffe49
commit 0a5604272d
5 changed files with 71 additions and 0 deletions
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7
arch/mips/kvm/mips.c
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@@ -48,6 +48,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "syscall", VCPU_STAT(syscall_exits), KVM_STAT_VCPU },
{ "resvd_inst", VCPU_STAT(resvd_inst_exits), KVM_STAT_VCPU },
{ "break_inst", VCPU_STAT(break_inst_exits), KVM_STAT_VCPU },
{ "trap_inst", VCPU_STAT(trap_inst_exits), KVM_STAT_VCPU },
{ "flush_dcache", VCPU_STAT(flush_dcache_exits), KVM_STAT_VCPU },
{ "halt_successful_poll", VCPU_STAT(halt_successful_poll), KVM_STAT_VCPU },
{ "halt_wakeup", VCPU_STAT(halt_wakeup), KVM_STAT_VCPU },
@@ -1119,6 +1120,12 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
ret = kvm_mips_callbacks->handle_break(vcpu);
break;
case T_TRAP:
++vcpu->stat.trap_inst_exits;
trace_kvm_exit(vcpu, TRAP_INST_EXITS);
ret = kvm_mips_callbacks->handle_trap(vcpu);
break;
case T_MSADIS:
ret = kvm_mips_callbacks->handle_msa_disabled(vcpu);
break;