Re: [PATCH 05/13] KVM: PPC: Book3S HV: Adapt to new HPTE format on POWER9

On Sat, Nov 19, 2016 at 11:38:40AM +1100, Balbir Singh wrote:

On 18/11/16 18:28, Paul Mackerras wrote:

quoted

This adapts the KVM-HV hashed page table (HPT) code to read and write
HPT entries in the new format defined in Power ISA v3.00 on POWER9
machines.  The new format moves the B (segment size) field from the
first doubleword to the second, and trims some bits from the AVA
(abbreviated virtual address) and ARPN (abbreviated real page number)
fields.  As far as possible, the conversion is done when reading or
writing the HPT entries, and the rest of the code continues to use
the old format.

[snip]

quoted

@@ -440,6 +442,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 {
 	struct kvm *kvm = vcpu->kvm;
 	unsigned long hpte[3], r;
+	unsigned long hnow_v, hnow_r;
 	__be64 *hptep;
 	unsigned long mmu_seq, psize, pte_size;
 	unsigned long gpa_base, gfn_base;

@@ -488,6 +491,10 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	unlock_hpte(hptep, hpte[0]);
 	preempt_enable();
 
+	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+		hpte[0] = hpte_new_to_old_v(hpte[0], hpte[1]);
+		hpte[1] = hpte_new_to_old_r(hpte[1]);
+	}

I think we can avoid this, if we avoid the conversion in kvmppc_hpte_hv_fault().
If we decide not to do this, then gpa will need to use a new mask to extract
the correct gpa.

Yes, we could store vcpu->arch.pgfault[] in native format, i.e. new
format on P9.  That might make the code a bit simpler indeed.

Paul.