xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

MIPS: KVM: Handle TRAP exceptions from guest kernel

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

36
arch/mips/kvm/emulate.c
View File

@@ -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;