KVM: PPC: Book3s PR: Allow access to unprivileged MMCR2 register

The MMCR2 register is available twice, one time with number 785
(privileged access), and one time with number 769 (unprivileged,
but it can be disabled completely). In former times, the Linux
kernel was using the unprivileged register 769 only, but since
commit 8dd75ccb571f3c92c ("powerpc: Use privileged SPR number
for MMCR2"), it uses the privileged register 785 instead.
The KVM-PR code then of course also switched to use the SPR 785,
but this is causing older guest kernels to crash, since these
kernels still access 769 instead. So to support older kernels
with KVM-PR again, we have to support register 769 in KVM-PR, too.

Fixes: 8dd75ccb571f3c92c48014b3dabd3d51a115ab41
Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index f69f40f..978dada 100644 (file)
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -737,6 +737,7 @@
 #define   MMCR0_FCHV   0x00000001UL /* freeze conditions in hypervisor mode */
 #define SPRN_MMCR1     798
 #define SPRN_MMCR2     785
+#define SPRN_UMMCR2    769
 #define SPRN_MMCRA     0x312
 #define   MMCRA_SDSYNC 0x80000000UL /* SDAR synced with SIAR */
 #define   MMCRA_SDAR_DCACHE_MISS 0x40000000UL

diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 7d9e4ed..8359752 100644 (file)
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -498,6 +498,7 @@ int kvmppc_core_emulate_mtspr_pr(struct kvm_vcpu *vcpu, int sprn, ulong spr_val)
        case SPRN_MMCR0:
        case SPRN_MMCR1:
        case SPRN_MMCR2:
+       case SPRN_UMMCR2:
 #endif
                break;
 unprivileged:
@@ -640,6 +641,7 @@ int kvmppc_core_emulate_mfspr_pr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val
        case SPRN_MMCR0:
        case SPRN_MMCR1:
        case SPRN_MMCR2:
+       case SPRN_UMMCR2:
        case SPRN_TIR:
 #endif
                *spr_val = 0;