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>

7 files changed, 34 insertions, 16 deletions

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 43e343e00fb88..8073267dc4a05 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 3a875fc1b63ca..2de96a180166e 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__ */
diff --git a/arch/arm/kvm/hyp/switch.c b/arch/arm/kvm/hyp/switch.c
index acf1c37fa49c2..3b058a5d7c5f1 100644
--- a/arch/arm/kvm/hyp/switch.c
+++ b/arch/arm/kvm/hyp/switch.c
@@ -77,7 +77,7 @@ static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
 static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
 {
 	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
-	write_sysreg(kvm->arch.vttbr, VTTBR);
+	write_sysreg(kvm_get_vttbr(kvm), VTTBR);
 	write_sysreg(vcpu->arch.midr, VPIDR);
 }
 
diff --git a/arch/arm/kvm/hyp/tlb.c b/arch/arm/kvm/hyp/tlb.c
index c0edd450e1045..8e4afba736357 100644
--- a/arch/arm/kvm/hyp/tlb.c
+++ b/arch/arm/kvm/hyp/tlb.c
@@ -41,7 +41,7 @@ void __hyp_text __kvm_tlb_flush_vmid(struct kvm *kvm)
 
 	/* Switch to requested VMID */
 	kvm = kern_hyp_va(kvm);
-	write_sysreg(kvm->arch.vttbr, VTTBR);
+	write_sysreg(kvm_get_vttbr(kvm), VTTBR);
 	isb();
 
 	write_sysreg(0, TLBIALLIS);
@@ -61,7 +61,7 @@ void __hyp_text __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu)
 	struct kvm *kvm = kern_hyp_va(kern_hyp_va(vcpu)->kvm);
 
 	/* Switch to requested VMID */
-	write_sysreg(kvm->arch.vttbr, VTTBR);
+	write_sysreg(kvm_get_vttbr(kvm), VTTBR);
 	isb();
 
 	write_sysreg(0, TLBIALL);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f497bb31031ff..444dd1cb19583 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -57,16 +57,19 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
 int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext);
 void __extended_idmap_trampoline(phys_addr_t boot_pgd, phys_addr_t idmap_start);
 
-struct kvm_arch {
+struct kvm_vmid {
 	/* The VMID generation used for the virt. memory system */
 	u64    vmid_gen;
 	u32    vmid;
+};
+
+struct kvm_arch {
+	struct kvm_vmid vmid;
 
 	/* stage2 entry level table */
 	pgd_t *pgd;
+	phys_addr_t pgd_phys;
 
-	/* VTTBR value associated with above pgd and vmid */
-	u64    vttbr;
 	/* VTCR_EL2 value for this VM */
 	u64    vtcr;
 
diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index a80a7ef573252..4da765f2cca58 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -21,6 +21,7 @@
 #include <linux/compiler.h>
 #include <linux/kvm_host.h>
 #include <asm/alternative.h>
+#include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>
 
 #define __hyp_text __section(.hyp.text) notrace
@@ -163,7 +164,7 @@ void __noreturn __hyp_do_panic(unsigned long, ...);
 static __always_inline void __hyp_text __load_guest_stage2(struct kvm *kvm)
 {
 	write_sysreg(kvm->arch.vtcr, vtcr_el2);
-	write_sysreg(kvm->arch.vttbr, vttbr_el2);
+	write_sysreg(kvm_get_vttbr(kvm), vttbr_el2);
 
 	/*
 	 * ARM erratum 1165522 requires the actual execution of the above
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 8af4b1befa421..c423c8c4fc398 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -591,9 +591,15 @@ static inline u64 kvm_vttbr_baddr_mask(struct kvm *kvm)
 	return vttbr_baddr_mask(kvm_phys_shift(kvm), kvm_stage2_levels(kvm));
 }
 
-static inline bool kvm_cpu_has_cnp(void)
+static __always_inline u64 kvm_get_vttbr(struct kvm *kvm)
 {
-	return system_supports_cnp();
+	struct kvm_vmid *vmid = &kvm->arch.vmid;
+	u64 vmid_field, baddr;
+	u64 cnp = system_supports_cnp() ? VTTBR_CNP_BIT : 0;
+
+	baddr = kvm->arch.pgd_phys;
+	vmid_field = (u64)vmid->vmid << VTTBR_VMID_SHIFT;
+	return kvm_phys_to_vttbr(baddr) | vmid_field | cnp;
 }
 
 #endif /* __ASSEMBLY__ */