arm/arm64: KVM: add 'writable' parameter to kvm_phys_addr_ioremap

Add support for read-only MMIO passthrough mappings by adding a
'writable' parameter to kvm_phys_addr_ioremap. For the moment,
mappings will be read-write even if 'writable' is false, but once
the definition of PAGE_S2_DEVICE gets changed, those mappings will
be created read-only.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

4 files changed, 8 insertions, 4 deletions

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 3f688b458143..eaa6deac97b2 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -50,7 +50,7 @@ void free_hyp_pgds(void);
 int kvm_alloc_stage2_pgd(struct kvm *kvm);
 void kvm_free_stage2_pgd(struct kvm *kvm);
 int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
-                          phys_addr_t pa, unsigned long size);
+                          phys_addr_t pa, unsigned long size, bool writable);
 
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
 
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index bb2e110e77c0..a7eabd1c4287 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -674,7 +674,7 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
  * @size:       The size of the mapping
  */
 int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
-                          phys_addr_t pa, unsigned long size)
+                          phys_addr_t pa, unsigned long size, bool writable)
 {
         phys_addr_t addr, end;
         int ret = 0;
@@ -687,6 +687,9 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
         for (addr = guest_ipa; addr < end; addr += PAGE_SIZE) {
                 pte_t pte = pfn_pte(pfn, PAGE_S2_DEVICE);
 
+                if (writable)
+                        kvm_set_s2pte_writable(&pte);
+
                 ret = mmu_topup_memory_cache(&cache, 2, 2);
                 if (ret)
                         goto out;
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index a030d163840b..e36171974d6a 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -77,7 +77,7 @@ void free_hyp_pgds(void);
 int kvm_alloc_stage2_pgd(struct kvm *kvm);
 void kvm_free_stage2_pgd(struct kvm *kvm);
 int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
-                          phys_addr_t pa, unsigned long size);
+                          phys_addr_t pa, unsigned long size, bool writable);
 
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
 
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 862967852d5a..382fb5a88b9c 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1899,7 +1899,8 @@ int kvm_vgic_init(struct kvm *kvm)
         }
 
         ret = kvm_phys_addr_ioremap(kvm, kvm->arch.vgic.vgic_cpu_base,
-                                    vgic->vcpu_base, KVM_VGIC_V2_CPU_SIZE);
+                                    vgic->vcpu_base, KVM_VGIC_V2_CPU_SIZE,
+                                    true);
         if (ret) {
                 kvm_err("Unable to remap VGIC CPU to VCPU\n");
                 goto out;