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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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8
arch/mips/include/asm/kvm_host.h
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@@ -119,6 +119,7 @@ struct kvm_vcpu_stat {
u32 syscall_exits;
u32 resvd_inst_exits;
u32 break_inst_exits;
u32 trap_inst_exits;
u32 flush_dcache_exits;
u32 halt_successful_poll;
u32 halt_wakeup;
@@ -138,6 +139,7 @@ enum kvm_mips_exit_types {
SYSCALL_EXITS,
RESVD_INST_EXITS,
BREAK_INST_EXITS,
TRAP_INST_EXITS,
FLUSH_DCACHE_EXITS,
MAX_KVM_MIPS_EXIT_TYPES
};
@@ -579,6 +581,7 @@ struct kvm_mips_callbacks {
int (*handle_syscall)(struct kvm_vcpu *vcpu);
int (*handle_res_inst)(struct kvm_vcpu *vcpu);
int (*handle_break)(struct kvm_vcpu *vcpu);
int (*handle_trap)(struct kvm_vcpu *vcpu);
int (*handle_msa_disabled)(struct kvm_vcpu *vcpu);
int (*vm_init)(struct kvm *kvm);
int (*vcpu_init)(struct kvm_vcpu *vcpu);
@@ -713,6 +716,11 @@ extern enum emulation_result kvm_mips_emulate_bp_exc(unsigned long cause,
struct kvm_run *run,
struct kvm_vcpu *vcpu);
extern enum emulation_result kvm_mips_emulate_trap_exc(unsigned long cause,
uint32_t *opc,
struct kvm_run *run,
struct kvm_vcpu *vcpu);
extern enum emulation_result kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu,
struct kvm_run *run);