KVM: arm64: Introduce __pkvm_host_relax_guest_perms()

Introduce a new hypercall allowing the host to relax the stage-2
permissions of mappings in a non-protected guest page-table. It will be
used later once we start allowing RO memslots and dirty logging.

Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20241218194059.3670226-13-qperret@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 0b6c4d325134723682f9603d4b2e8ed45ae1daf2..66ee8542dcc9d740a45c117066496677d6d47ea9 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -67,6 +67,7 @@ enum __kvm_host_smccc_func {
        __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
        __KVM_HOST_SMCCC_FUNC___pkvm_host_share_guest,
        __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_guest,
+       __KVM_HOST_SMCCC_FUNC___pkvm_host_relax_perms_guest,
        __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
        __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
        __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index e6d080b71779a75119ddf41f4cdc60154eddb4e9..181aec2d5bc1a1b8e2b155c20eb12f43ef31c72b 100644 (file)
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -42,6 +42,7 @@ int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
 int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu,
                            enum kvm_pgtable_prot prot);
 int __pkvm_host_unshare_guest(u64 gfn, struct pkvm_hyp_vm *hyp_vm);
+int __pkvm_host_relax_perms_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_pgtable_prot prot);
 
 bool addr_is_memory(phys_addr_t phys);
 int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 3c3a27c985a2e23effd4d968f7d5b81f91094a7b..287e4ee93ef2198bd6389bb08d29bee50e0c73fa 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -264,6 +264,25 @@ out:
        cpu_reg(host_ctxt, 1) =  ret;
 }
 
+static void handle___pkvm_host_relax_perms_guest(struct kvm_cpu_context *host_ctxt)
+{
+       DECLARE_REG(u64, gfn, host_ctxt, 1);
+       DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 2);
+       struct pkvm_hyp_vcpu *hyp_vcpu;
+       int ret = -EINVAL;
+
+       if (!is_protected_kvm_enabled())
+               goto out;
+
+       hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
+       if (!hyp_vcpu || pkvm_hyp_vcpu_is_protected(hyp_vcpu))
+               goto out;
+
+       ret = __pkvm_host_relax_perms_guest(gfn, hyp_vcpu, prot);
+out:
+       cpu_reg(host_ctxt, 1) = ret;
+}
+
 static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt)
 {
        DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
@@ -475,6 +494,7 @@ static const hcall_t host_hcall[] = {
        HANDLE_FUNC(__pkvm_host_unshare_hyp),
        HANDLE_FUNC(__pkvm_host_share_guest),
        HANDLE_FUNC(__pkvm_host_unshare_guest),
+       HANDLE_FUNC(__pkvm_host_relax_perms_guest),
        HANDLE_FUNC(__kvm_adjust_pc),
        HANDLE_FUNC(__kvm_vcpu_run),
        HANDLE_FUNC(__kvm_flush_vm_context),

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 30243b7922f141e3945f66e6589ece53045f5b93..aa8e0408aebb564a2a8e928b7c7028069b5f2374 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -1488,3 +1488,26 @@ unlock:
 
        return ret;
 }
+
+int __pkvm_host_relax_perms_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_pgtable_prot prot)
+{
+       struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
+       u64 ipa = hyp_pfn_to_phys(gfn);
+       u64 phys;
+       int ret;
+
+       if (prot & ~KVM_PGTABLE_PROT_RWX)
+               return -EINVAL;
+
+       host_lock_component();
+       guest_lock_component(vm);
+
+       ret = __check_host_shared_guest(vm, &phys, ipa);
+       if (!ret)
+               ret = kvm_pgtable_stage2_relax_perms(&vm->pgt, ipa, prot, 0);
+
+       guest_unlock_component(vm);
+       host_unlock_component();
+
+       return ret;
+}