Re: [PATCH v3 17/33] KVM: PPC: Book3S HV: Framework and hcall stubs for nested virtualization

On Tue, Oct 02, 2018 at 09:31:16PM +1000, Paul Mackerras wrote:

This starts the process of adding the code to support nested HV-style
virtualization.  It defines a new H_SET_PARTITION_TABLE hypercall which
a nested hypervisor can use to set the base address and size of a
partition table in its memory (analogous to the PTCR register).
On the host (level 0 hypervisor) side, the H_SET_PARTITION_TABLE
hypercall from the guest is handled by code that saves the virtual
PTCR value for the guest.

This also adds code for creating and destroying nested guests and for
reading the partition table entry for a nested guest from L1 memory.
Each nested guest has its own shadow LPID value, different in general
from the LPID value used by the nested hypervisor to refer to it.  The
shadow LPID value is allocated at nested guest creation time.

Nested hypervisor functionality is only available for a radix guest,
which therefore means a radix host on a POWER9 (or later) processor.

Signed-off-by: Paul Mackerras <redacted>

Reviewed-by: David Gibson <redacted>

Couple of nits noted below

[snip]

+void kvmhv_set_ptbl_entry(unsigned int lpid, u64 dw0, u64 dw1)
+{
+	if (cpu_has_feature(CPU_FTR_HVMODE)) {
+		mmu_partition_table_set_entry(lpid, dw0, dw1);
+	} else {
+		pseries_partition_tb[lpid].patb0 = cpu_to_be64(dw0);
+		pseries_partition_tb[lpid].patb1 = cpu_to_be64(dw1);
+		/* this will be emulated, L0 will do the necessary barriers */
+		asm volatile(PPC_TLBIE_5(%0, %1, 2, 0, 1) : :
+			     "r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));

It seems a bit odd to me to introduce this with a mechanism we never
actually implement, then replace it.  But I guess if refolding the
series is painful..

+	}

[snip]

+/*
+ * Handle the H_SET_PARTITION_TABLE hcall.
+ * r4 = guest real address of partition table + log_2(size) - 12
+ * (formatted as for the PTCR).
+ */
+long kvmhv_set_partition_table(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+	unsigned long ptcr = kvmppc_get_gpr(vcpu, 4);
+
+	kvm->arch.l1_ptcr = ptcr;

Still no validation here.

+	return H_SUCCESS;
+}

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson