KVM: PPC: Book3S HV: Add NO_HASH flag to GET_SMMU_INFO ioctl result

paulusmack · paulusmack · commit 901f8c3f6feb · 2018-10-09T16:14:54.000+11:00
This adds a KVM_PPC_NO_HASH flag to the flags field of the
kvm_ppc_smmu_info struct, and arranges for it to be set when
running as a nested hypervisor, as an unambiguous indication
to userspace that HPT guests are not supported.  Reporting the
KVM_CAP_PPC_MMU_HASH_V3 capability as false could be taken as
indicating only that the new HPT features in ISA V3.0 are not
supported, leaving it ambiguous whether pre-V3.0 HPT features
are supported.

Reviewed-by: David Gibson &lt;david@gibson.dropbear.id.au&gt;
Signed-off-by: Paul Mackerras &lt;paulus@ozlabs.org&gt;
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
@@ -2270,6 +2270,10 @@ The supported flags are:
         The emulated MMU supports 1T segments in addition to the
         standard 256M ones.
 
+    - KVM_PPC_NO_HASH
+	This flag indicates that HPT guests are not supported by KVM,
+	thus all guests must use radix MMU mode.
+
 The "slb_size" field indicates how many SLB entries are supported
 
 The "sps" array contains 8 entries indicating the supported base
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
@@ -4257,6 +4257,10 @@ static int kvm_vm_ioctl_get_smmu_info_hv(struct kvm *kvm,
 	kvmppc_add_seg_page_size(&sps, 16, SLB_VSID_L | SLB_VSID_LP_01);
 	kvmppc_add_seg_page_size(&sps, 24, SLB_VSID_L);
 
+	/* If running as a nested hypervisor, we don't support HPT guests */
+	if (kvmhv_on_pseries())
+		info->flags |= KVM_PPC_NO_HASH;
+
 	return 0;
 }
 
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
@@ -719,6 +719,7 @@ struct kvm_ppc_one_seg_page_size {
 
 #define KVM_PPC_PAGE_SIZES_REAL		0x00000001
 #define KVM_PPC_1T_SEGMENTS		0x00000002
+#define KVM_PPC_NO_HASH			0x00000004
 
 struct kvm_ppc_smmu_info {
 	__u64 flags;

Original file line number	Diff line number	Diff line change
`@@ -4257,6 +4257,10 @@ static int kvm_vm_ioctl_get_smmu_info_hv(struct kvm *kvm,`
`4257`	`4257`	`kvmppc_add_seg_page_size(&sps, 16, SLB_VSID_L \| SLB_VSID_LP_01);`
`4258`	`4258`	`kvmppc_add_seg_page_size(&sps, 24, SLB_VSID_L);`
`4259`	`4259`
	`4260`	`+ /* If running as a nested hypervisor, we don't support HPT guests */`
	`4261`	`+ if (kvmhv_on_pseries())`
	`4262`	`+ info->flags \|= KVM_PPC_NO_HASH;`
	`4263`	`+`
`4260`	`4264`	`return 0;`
`4261`	`4265`	`}`
`4262`	`4266`