KVM: PPC: Book3S HV: Report storage key support to userspace

This adds information about storage keys to the struct returned by
the KVM_PPC_GET_SMMU_INFO ioctl.  The new fields replace a pad field,
which was zeroed by previous kernel versions.  Thus userspace that
knows about the new fields will see zeroes when running on an older
kernel, indicating that storage keys are not supported.  The size of
the structure has not changed.

The number of keys is hard-coded for the CPUs supported by HV KVM,
which is just POWER7, POWER8 and POWER9.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_hv.c

@@ -3331,6 +3331,14 @@ static int kvm_vm_ioctl_get_smmu_info_hv(struct kvm *kvm,
 	if (radix_enabled())
 		return -EINVAL;
 
+	/*
+	 * POWER7, POWER8 and POWER9 all support 32 storage keys for data.
+	 * POWER7 doesn't support keys for instruction accesses,
+	 * POWER8 and POWER9 do.
+	 */
+	info->data_keys = 32;
+	info->instr_keys = cpu_has_feature(CPU_FTR_ARCH_207S) ? 32 : 0;
+
 	info->flags = KVM_PPC_PAGE_SIZES_REAL;
 	if (mmu_has_feature(MMU_FTR_1T_SEGMENT))
 		info->flags |= KVM_PPC_1T_SEGMENTS;

include/uapi/linux/kvm.h

@@ -711,7 +711,8 @@ struct kvm_ppc_one_seg_page_size {
 struct kvm_ppc_smmu_info {
 	__u64 flags;
 	__u32 slb_size;
-	__u32 pad;
+	__u16 data_keys;	/* # storage keys supported for data */
+	__u16 instr_keys;	/* # storage keys supported for instructions */
 	struct kvm_ppc_one_seg_page_size sps[KVM_PPC_PAGE_SIZES_MAX_SZ];
 };