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authorJames Hogan <james.hogan@imgtec.com>2014-03-14 13:06:09 (GMT)
committerPaolo Bonzini <pbonzini@redhat.com>2014-03-19 16:01:43 (GMT)
commit26f4f3b57862642296a2e613674e7f00d91c022f (patch)
tree34eff1982a3d9fcfd65a8f9d8a14bd6f87fd3949 /arch/mips/kvm
parent15505679362270d02c449626385cb74af8905514 (diff)
downloadlinux-26f4f3b57862642296a2e613674e7f00d91c022f.tar.xz
MIPS: KVM: Consult HWREna before emulating RDHWR
The ability to read hardware registers from userland with the RDHWR instruction should depend upon the corresponding bit of the HWREna register being set, otherwise a reserved instruction exception should be generated. However KVM's current emulation ignores the guest's HWREna and always emulates RDHWR instructions even if the guest OS has disallowed them. Therefore rework the RDHWR emulation code to check for privilege or the corresponding bit in the guest HWREna bit. Also remove the #if 0 case for the UserLocal register. I presume it was there for debug purposes but it seems unnecessary now that the guest can control whether it causes a guest exception. Signed-off-by: James Hogan <james.hogan@imgtec.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sanjay Lal <sanjayl@kymasys.com> Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/mips/kvm')
-rw-r--r--arch/mips/kvm/kvm_mips_emul.c30
1 files changed, 16 insertions, 14 deletions
diff --git a/arch/mips/kvm/kvm_mips_emul.c b/arch/mips/kvm/kvm_mips_emul.c
index e75ef82..d562572 100644
--- a/arch/mips/kvm/kvm_mips_emul.c
+++ b/arch/mips/kvm/kvm_mips_emul.c
@@ -1542,8 +1542,15 @@ kvm_mips_handle_ri(unsigned long cause, uint32_t *opc,
}
if ((inst & OPCODE) == SPEC3 && (inst & FUNC) == RDHWR) {
+ int usermode = !KVM_GUEST_KERNEL_MODE(vcpu);
int rd = (inst & RD) >> 11;
int rt = (inst & RT) >> 16;
+ /* If usermode, check RDHWR rd is allowed by guest HWREna */
+ if (usermode && !(kvm_read_c0_guest_hwrena(cop0) & BIT(rd))) {
+ kvm_debug("RDHWR %#x disallowed by HWREna @ %p\n",
+ rd, opc);
+ goto emulate_ri;
+ }
switch (rd) {
case 0: /* CPU number */
arch->gprs[rt] = 0;
@@ -1567,32 +1574,27 @@ kvm_mips_handle_ri(unsigned long cause, uint32_t *opc,
}
break;
case 29:
-#if 1
arch->gprs[rt] = kvm_read_c0_guest_userlocal(cop0);
-#else
- /* UserLocal not implemented */
- er = EMULATE_FAIL;
-#endif
break;
default:
kvm_debug("RDHWR %#x not supported @ %p\n", rd, opc);
- er = EMULATE_FAIL;
- break;
+ goto emulate_ri;
}
} else {
kvm_debug("Emulate RI not supported @ %p: %#x\n", opc, inst);
- er = EMULATE_FAIL;
+ goto emulate_ri;
}
+ return EMULATE_DONE;
+
+emulate_ri:
/*
- * Rollback PC only if emulation was unsuccessful
+ * Rollback PC (if in branch delay slot then the PC already points to
+ * branch target), and pass the RI exception to the guest OS.
*/
- if (er == EMULATE_FAIL) {
- vcpu->arch.pc = curr_pc;
- er = kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
- }
- return er;
+ vcpu->arch.pc = curr_pc;
+ return kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
}
enum emulation_result