[PATCH 3/6] arm/arm64: KVM: add 'writable' parameter to kvm_phys_addr_ioremap

[ard.biesheuvel@linaro.org (Ard Biesheuvel)]

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.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm/kvm/mmu.c               | 5 ++++-
 arch/arm64/include/asm/kvm_mmu.h | 2 +-
 virt/kvm/arm/vgic.c              | 3 ++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index c093e95ff7ef..fe53c3a30383 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 737da742b293..7474e611bb2a 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -78,7 +78,7 @@ 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 73eba793b17f..c2bdbf4e25c2 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1628,7 +1628,8 @@ 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;
-- 
1.8.3.2