diff options
authorPaul Mackerras <paulus@ozlabs.org>2017-06-15 16:10:27 +1000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-06-29 12:48:51 +0200
commit824b9506e4f27bf63dea55f1af27a2a75ff8934e (patch)
parent7b88f761929e86813c2a1eb878dcc17abbb6119f (diff)
KVM: PPC: Book3S HV: Preserve userspace HTM state properly
commit 46a704f8409f79fd66567ad3f8a7304830a84293 upstream. If userspace attempts to call the KVM_RUN ioctl when it has hardware transactional memory (HTM) enabled, the values that it has put in the HTM-related SPRs TFHAR, TFIAR and TEXASR will get overwritten by guest values. To fix this, we detect this condition and save those SPR values in the thread struct, and disable HTM for the task. If userspace goes to access those SPRs or the HTM facility in future, a TM-unavailable interrupt will occur and the handler will reload those SPRs and re-enable HTM. If userspace has started a transaction and suspended it, we would currently lose the transactional state in the guest entry path and would almost certainly get a "TM Bad Thing" interrupt, which would cause the host to crash. To avoid this, we detect this case and return from the KVM_RUN ioctl with an EINVAL error, with the KVM exit reason set to KVM_EXIT_FAIL_ENTRY. Fixes: b005255e12a3 ("KVM: PPC: Book3S HV: Context-switch new POWER8 SPRs", 2014-01-08) Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 3c3a367b6e59..396dc44e783b 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2693,6 +2693,27 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
return -EINVAL;
+ /*
+ * Don't allow entry with a suspended transaction, because
+ * the guest entry/exit code will lose it.
+ * If the guest has TM enabled, save away their TM-related SPRs
+ * (they will get restored by the TM unavailable interrupt).
+ */
+ if (cpu_has_feature(CPU_FTR_TM) && current->thread.regs &&
+ (current->thread.regs->msr & MSR_TM)) {
+ if (MSR_TM_ACTIVE(current->thread.regs->msr)) {
+ run->exit_reason = KVM_EXIT_FAIL_ENTRY;
+ run->fail_entry.hardware_entry_failure_reason = 0;
+ return -EINVAL;
+ }
+ current->thread.tm_tfhar = mfspr(SPRN_TFHAR);
+ current->thread.tm_tfiar = mfspr(SPRN_TFIAR);
+ current->thread.tm_texasr = mfspr(SPRN_TEXASR);
+ current->thread.regs->msr &= ~MSR_TM;
+ }
/* No need to go into the guest when all we'll do is come back out */