KVM: arm/arm64: Factor out VMID into struct kvm_vmid

In preparation for nested virtualization where we are going to have more
than a single VMID per VM, let's factor out the VMID data into a
separate VMID data structure and change the VMID allocator to operate on
this new structure instead of using a struct kvm.

This also means that udate_vttbr now becomes update_vmid, and that the
vttbr itself is generated on the fly based on the stage 2 page table
base address and the vmid.

We cache the physical address of the pgd when allocating the pgd to
avoid doing the calculation on every entry to the guest and to avoid
calling into potentially non-hyp-mapped code from hyp/EL2.

If we wanted to merge the VMID allocator with the arm64 ASID allocator
at some point in the future, it should actually become easier to do that
after this patch.

Note that to avoid mapping the kvm_vmid_bits variable into hyp, we
simply forego the masking of the vmid value in kvm_get_vttbr and rely on
update_vmid to always assign a valid vmid value (within the supported
range).

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
[maz: minor cleanups]
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

2 files changed, 15 insertions, 7 deletions

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 43e343e00fb8..8073267dc4a0 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -57,10 +57,13 @@ int __attribute_const__ kvm_target_cpu(void);
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
 void kvm_reset_coprocs(struct kvm_vcpu *vcpu);
 
-struct kvm_arch {
-	/* VTTBR value associated with below pgd and vmid */
-	u64    vttbr;
+struct kvm_vmid {
+	/* The VMID generation used for the virt. memory system */
+	u64    vmid_gen;
+	u32    vmid;
+};
 
+struct kvm_arch {
 	/* The last vcpu id that ran on each physical CPU */
 	int __percpu *last_vcpu_ran;
 
@@ -70,11 +73,11 @@ struct kvm_arch {
 	 */
 
 	/* The VMID generation used for the virt. memory system */
-	u64    vmid_gen;
-	u32    vmid;
+	struct kvm_vmid vmid;
 
 	/* Stage-2 page table */
 	pgd_t *pgd;
+	phys_addr_t pgd_phys;
 
 	/* Interrupt controller */
 	struct vgic_dist	vgic;
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 3a875fc1b63c..2de96a180166 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -421,9 +421,14 @@ static inline int hyp_map_aux_data(void)
 
 static inline void kvm_set_ipa_limit(void) {}
 
-static inline bool kvm_cpu_has_cnp(void)
+static __always_inline u64 kvm_get_vttbr(struct kvm *kvm)
 {
-	return false;
+	struct kvm_vmid *vmid = &kvm->arch.vmid;
+	u64 vmid_field, baddr;
+
+	baddr = kvm->arch.pgd_phys;
+	vmid_field = (u64)vmid->vmid << VTTBR_VMID_SHIFT;
+	return kvm_phys_to_vttbr(baddr) | vmid_field;
 }
 
 #endif	/* !__ASSEMBLY__ */