| Message ID | 20200520174308.77820-1-ldufour@linux.ibm.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [v2] KVM: PPC: Book3S HV: relax check on H_SVM_INIT_ABORT | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (7b06fb8795ffea9d12be45a172197c3307955479) |
| snowpatch_ozlabs/build-ppc64le | warning | Build succeeded but added 1 new sparse warnings |
| snowpatch_ozlabs/build-ppc64be | warning | Build succeeded but added 1 new sparse warnings |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 15 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch fixes a commit that hasn't been released yet |
On Wed, 20 May 2020 19:43:08 +0200 Laurent Dufour <ldufour@linux.ibm.com> wrote: > The commit 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* > Hcalls") added checks of secure bit of SRR1 to filter out the Hcall > reserved to the Ultravisor. > > However, the Hcall H_SVM_INIT_ABORT is made by the Ultravisor passing the > context of the VM calling UV_ESM. This allows the Hypervisor to return to > the guest without going through the Ultravisor. Thus the Secure bit of SRR1 > is not set in that particular case. > > In the case a regular VM is calling H_SVM_INIT_ABORT, this hcall will be > filtered out in kvmppc_h_svm_init_abort() because kvm->arch.secure_guest is > not set in that case. > > Fixes: 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls") > Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> > --- Reviewed-by: Greg Kurz <groug@kaod.org> > arch/powerpc/kvm/book3s_hv.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 93493f0cbfe8..6ad1a3b14300 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -1099,9 +1099,12 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) > ret = kvmppc_h_svm_init_done(vcpu->kvm); > break; > case H_SVM_INIT_ABORT: > - ret = H_UNSUPPORTED; > - if (kvmppc_get_srr1(vcpu) & MSR_S) > - ret = kvmppc_h_svm_init_abort(vcpu->kvm); > + /* > + * Even if that call is made by the Ultravisor, the SSR1 value > + * is the guest context one, with the secure bit clear as it has > + * not yet been secured. So we can't check it here. > + */ > + ret = kvmppc_h_svm_init_abort(vcpu->kvm); > break; > > default:
On Wed, May 20, 2020 at 07:43:08PM +0200, Laurent Dufour wrote: > The commit 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* > Hcalls") added checks of secure bit of SRR1 to filter out the Hcall > reserved to the Ultravisor. > > However, the Hcall H_SVM_INIT_ABORT is made by the Ultravisor passing the > context of the VM calling UV_ESM. This allows the Hypervisor to return to > the guest without going through the Ultravisor. Thus the Secure bit of SRR1 > is not set in that particular case. > > In the case a regular VM is calling H_SVM_INIT_ABORT, this hcall will be > filtered out in kvmppc_h_svm_init_abort() because kvm->arch.secure_guest is > not set in that case. > > Fixes: 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls") > Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> Reviewed-by: Ram Pai <linuxram@us.ibm.com> > --- > arch/powerpc/kvm/book3s_hv.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 93493f0cbfe8..6ad1a3b14300 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -1099,9 +1099,12 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) > ret = kvmppc_h_svm_init_done(vcpu->kvm); > break; > case H_SVM_INIT_ABORT: > - ret = H_UNSUPPORTED; > - if (kvmppc_get_srr1(vcpu) & MSR_S) > - ret = kvmppc_h_svm_init_abort(vcpu->kvm); > + /* > + * Even if that call is made by the Ultravisor, the SSR1 value > + * is the guest context one, with the secure bit clear as it has > + * not yet been secured. So we can't check it here. > + */ Frankly speaking, the comment above when read in isolation; i.e without the delete code above, feels out of place. The reasoning for change is anyway captured in the changelog. So, I think, we should delete this comment. Also the comment above assumes the Ultravisor will call H_SVM_INIT_ABORT with SRR1(S) bit not set; which may or may not be true. Regardless of who and how H_SVM_INIT_ABORT is called, we should just call kvmppc_h_svm_init_abort() and let it deal with the complexities. RP
On Wed, May 20, 2020 at 07:43:08PM +0200, Laurent Dufour wrote: > The commit 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* > Hcalls") added checks of secure bit of SRR1 to filter out the Hcall > reserved to the Ultravisor. > > However, the Hcall H_SVM_INIT_ABORT is made by the Ultravisor passing the > context of the VM calling UV_ESM. This allows the Hypervisor to return to > the guest without going through the Ultravisor. Thus the Secure bit of SRR1 > is not set in that particular case. > > In the case a regular VM is calling H_SVM_INIT_ABORT, this hcall will be > filtered out in kvmppc_h_svm_init_abort() because kvm->arch.secure_guest is > not set in that case. > > Fixes: 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls") > Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> Thanks, applied to my kvm-ppc-next branch. I expanded the comment in the code a little. Paul.
Le 27/05/2020 à 06:16, Paul Mackerras a écrit : > On Wed, May 20, 2020 at 07:43:08PM +0200, Laurent Dufour wrote: >> The commit 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* >> Hcalls") added checks of secure bit of SRR1 to filter out the Hcall >> reserved to the Ultravisor. >> >> However, the Hcall H_SVM_INIT_ABORT is made by the Ultravisor passing the >> context of the VM calling UV_ESM. This allows the Hypervisor to return to >> the guest without going through the Ultravisor. Thus the Secure bit of SRR1 >> is not set in that particular case. >> >> In the case a regular VM is calling H_SVM_INIT_ABORT, this hcall will be >> filtered out in kvmppc_h_svm_init_abort() because kvm->arch.secure_guest is >> not set in that case. >> >> Fixes: 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls") >> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> > > Thanks, applied to my kvm-ppc-next branch. I expanded the comment in > the code a little. Thanks, the comment is more explicit now. Laurent.
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 93493f0cbfe8..6ad1a3b14300 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1099,9 +1099,12 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) ret = kvmppc_h_svm_init_done(vcpu->kvm); break; case H_SVM_INIT_ABORT: - ret = H_UNSUPPORTED; - if (kvmppc_get_srr1(vcpu) & MSR_S) - ret = kvmppc_h_svm_init_abort(vcpu->kvm); + /* + * Even if that call is made by the Ultravisor, the SSR1 value + * is the guest context one, with the secure bit clear as it has + * not yet been secured. So we can't check it here. + */ + ret = kvmppc_h_svm_init_abort(vcpu->kvm); break; default:
The commit 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls") added checks of secure bit of SRR1 to filter out the Hcall reserved to the Ultravisor. However, the Hcall H_SVM_INIT_ABORT is made by the Ultravisor passing the context of the VM calling UV_ESM. This allows the Hypervisor to return to the guest without going through the Ultravisor. Thus the Secure bit of SRR1 is not set in that particular case. In the case a regular VM is calling H_SVM_INIT_ABORT, this hcall will be filtered out in kvmppc_h_svm_init_abort() because kvm->arch.secure_guest is not set in that case. Fixes: 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls") Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> --- arch/powerpc/kvm/book3s_hv.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)