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

[David Gibson <david@gibson.dropbear.id.au>]

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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 <paulus@ozlabs.org>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

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

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