KVM: arm64: Introduce __pkvm_host_donate_guest()

In preparation for supporting protected VMs, whose memory pages are
isolated from the host, introduce a new pKVM hypercall to allow the
donation of pages to a guest.

Tested-by: Fuad Tabba <tabba@google.com>
Tested-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://patch.msgid.link/20260330144841.26181-13-will@kernel.org
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 df6b661701b6f736ac73c12b378c0148f3707359..dfc6625c82697718023610eaade7fe6865645771 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -79,6 +79,7 @@ enum __kvm_host_smccc_func {
        /* Hypercalls that are available only when pKVM has finalised. */
        __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
        __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
+       __KVM_HOST_SMCCC_FUNC___pkvm_host_donate_guest,
        __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,

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index c201168f28577e66b330546473bff0e6acfad714..50caca311ef5fa039d3fd97e1f9f05d1ee88e970 100644 (file)
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -100,7 +100,7 @@ typedef u64 kvm_pte_t;
                                         KVM_PTE_LEAF_ATTR_HI_S2_XN)
 
 #define KVM_INVALID_PTE_OWNER_MASK     GENMASK(9, 2)
-#define KVM_MAX_OWNER_ID               1
+#define KVM_MAX_OWNER_ID               2
 
 /*
  * Used to indicate a pte for which a 'break-before-make' sequence is in

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index 7f25f2bca90cb58354b8f517f9ffcd039ef11121..7061b0be340a9cfc0a36b77175eb05a74d9f9325 100644 (file)
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -27,6 +27,7 @@ extern struct host_mmu host_mmu;
 enum pkvm_component_id {
        PKVM_ID_HOST,
        PKVM_ID_HYP,
+       PKVM_ID_GUEST,
 };
 
 extern unsigned long hyp_nr_cpus;
@@ -38,6 +39,7 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
 int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
 int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
 int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
+int __pkvm_host_donate_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu);
 int __pkvm_host_share_guest(u64 pfn, u64 gfn, u64 nr_pages, struct pkvm_hyp_vcpu *vcpu,
                            enum kvm_pgtable_prot prot);
 int __pkvm_host_unshare_guest(u64 gfn, u64 nr_pages, struct pkvm_hyp_vm *hyp_vm);

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 634ea27662407bb38b85753d676dc5f877b2e516..970656318cf2511e0112fe0110ee4d8ac0564248 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -241,6 +241,26 @@ static int pkvm_refill_memcache(struct pkvm_hyp_vcpu *hyp_vcpu)
                               &host_vcpu->arch.pkvm_memcache);
 }
 
+static void handle___pkvm_host_donate_guest(struct kvm_cpu_context *host_ctxt)
+{
+       DECLARE_REG(u64, pfn, host_ctxt, 1);
+       DECLARE_REG(u64, gfn, host_ctxt, 2);
+       struct pkvm_hyp_vcpu *hyp_vcpu;
+       int ret = -EINVAL;
+
+       hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
+       if (!hyp_vcpu || !pkvm_hyp_vcpu_is_protected(hyp_vcpu))
+               goto out;
+
+       ret = pkvm_refill_memcache(hyp_vcpu);
+       if (ret)
+               goto out;
+
+       ret = __pkvm_host_donate_guest(pfn, gfn, hyp_vcpu);
+out:
+       cpu_reg(host_ctxt, 1) =  ret;
+}
+
 static void handle___pkvm_host_share_guest(struct kvm_cpu_context *host_ctxt)
 {
        DECLARE_REG(u64, pfn, host_ctxt, 1);
@@ -595,6 +615,7 @@ static const hcall_t host_hcall[] = {
 
        HANDLE_FUNC(__pkvm_host_share_hyp),
        HANDLE_FUNC(__pkvm_host_unshare_hyp),
+       HANDLE_FUNC(__pkvm_host_donate_guest),
        HANDLE_FUNC(__pkvm_host_share_guest),
        HANDLE_FUNC(__pkvm_host_unshare_guest),
        HANDLE_FUNC(__pkvm_host_relax_perms_guest),

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 7d22893ab1dcefe06e5e459becbd7a8e530c0dfb..03e6fa124253a057fb32a2e9ad594306fd14ea63 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -971,6 +971,36 @@ static int __guest_check_transition_size(u64 phys, u64 ipa, u64 nr_pages, u64 *s
        return 0;
 }
 
+int __pkvm_host_donate_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu)
+{
+       struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
+       u64 phys = hyp_pfn_to_phys(pfn);
+       u64 ipa = hyp_pfn_to_phys(gfn);
+       int ret;
+
+       host_lock_component();
+       guest_lock_component(vm);
+
+       ret = __host_check_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_OWNED);
+       if (ret)
+               goto unlock;
+
+       ret = __guest_check_page_state_range(vm, ipa, PAGE_SIZE, PKVM_NOPAGE);
+       if (ret)
+               goto unlock;
+
+       WARN_ON(host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_GUEST));
+       WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys,
+                                      pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_OWNED),
+                                      &vcpu->vcpu.arch.pkvm_memcache, 0));
+
+unlock:
+       guest_unlock_component(vm);
+       host_unlock_component();
+
+       return ret;
+}
+
 int __pkvm_host_share_guest(u64 pfn, u64 gfn, u64 nr_pages, struct pkvm_hyp_vcpu *vcpu,
                            enum kvm_pgtable_prot prot)
 {