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author | James Hogan <james.hogan@imgtec.com> | 2015-02-06 16:03:57 +0000 |
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committer | James Hogan <james.hogan@imgtec.com> | 2015-03-27 21:25:07 +0000 |
commit | 0a5604272d80c985f87de959f0bb7e36fd53d3c7 (patch) | |
tree | 391bbee989a6ab6ab22d7b4b32a0b7850602d5be /arch/mips/kvm/emulate.c | |
parent | 64bedffe496820dbb6b53302d80dd0f04db33d8e (diff) | |
download | talos-op-linux-0a5604272d80c985f87de959f0bb7e36fd53d3c7.tar.gz talos-op-linux-0a5604272d80c985f87de959f0bb7e36fd53d3c7.zip |
MIPS: KVM: Handle TRAP exceptions from guest kernel
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
Diffstat (limited to 'arch/mips/kvm/emulate.c')
-rw-r--r-- | arch/mips/kvm/emulate.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c index 838d3a6a5b7d..33e132dc7de8 100644 --- a/arch/mips/kvm/emulate.c +++ b/arch/mips/kvm/emulate.c @@ -1970,6 +1970,41 @@ enum emulation_result kvm_mips_emulate_bp_exc(unsigned long cause, return er; } +enum emulation_result kvm_mips_emulate_trap_exc(unsigned long cause, + uint32_t *opc, + struct kvm_run *run, + struct kvm_vcpu *vcpu) +{ + struct mips_coproc *cop0 = vcpu->arch.cop0; + struct kvm_vcpu_arch *arch = &vcpu->arch; + enum emulation_result er = EMULATE_DONE; + + if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) { + /* save old pc */ + kvm_write_c0_guest_epc(cop0, arch->pc); + kvm_set_c0_guest_status(cop0, ST0_EXL); + + if (cause & CAUSEF_BD) + kvm_set_c0_guest_cause(cop0, CAUSEF_BD); + else + kvm_clear_c0_guest_cause(cop0, CAUSEF_BD); + + kvm_debug("Delivering TRAP @ pc %#lx\n", arch->pc); + + kvm_change_c0_guest_cause(cop0, (0xff), + (T_TRAP << CAUSEB_EXCCODE)); + + /* Set PC to the exception entry point */ + arch->pc = KVM_GUEST_KSEG0 + 0x180; + + } else { + kvm_err("Trying to deliver TRAP when EXL is already set\n"); + er = EMULATE_FAIL; + } + + return er; +} + /* ll/sc, rdhwr, sync emulation */ #define OPCODE 0xfc000000 @@ -2176,6 +2211,7 @@ enum emulation_result kvm_mips_check_privilege(unsigned long cause, case T_SYSCALL: case T_BREAK: case T_RES_INST: + case T_TRAP: case T_MSADIS: break; |