Merge branch kvm-arm64/pkvm-hyp-sharing into kvmarm-master/next

* kvm-arm64/pkvm-hyp-sharing:
  : .
  : Series from Quentin Perret, implementing HYP page share/unshare:
  :
  : This series implements an unshare hypercall at EL2 in nVHE
  : protected mode, and makes use of it to unmmap guest-specific
  : data-structures from EL2 stage-1 during guest tear-down.
  : Crucially, the implementation of the share and unshare
  : routines use page refcounts in the host kernel to avoid
  : accidentally unmapping data-structures that overlap a common
  : page.
  : [...]
  : .
  KVM: arm64: pkvm: Unshare guest structs during teardown
  KVM: arm64: Expose unshare hypercall to the host
  KVM: arm64: Implement do_unshare() helper for unsharing memory
  KVM: arm64: Implement __pkvm_host_share_hyp() using do_share()
  KVM: arm64: Implement do_share() helper for sharing memory
  KVM: arm64: Introduce wrappers for host and hyp spin lock accessors
  KVM: arm64: Extend pkvm_page_state enumeration to handle absent pages
  KVM: arm64: pkvm: Refcount the pages shared with EL2
  KVM: arm64: Introduce kvm_share_hyp()
  KVM: arm64: Implement kvm_pgtable_hyp_unmap() at EL2
  KVM: arm64: Hook up ->page_count() for hypervisor stage-1 page-table
  KVM: arm64: Fixup hyp stage-1 refcount
  KVM: arm64: Refcount hyp stage-1 pgtable pages
  KVM: arm64: Provide {get,put}_page() stubs for early hyp allocator

Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/include/asm/kvm_asm.h

@@ -63,6 +63,7 @@ enum __kvm_host_smccc_func {
 
 	/* Hypercalls available after pKVM finalisation */
 	__KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
+	__KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
 	__KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
 	__KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
 	__KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,

arch/arm64/include/asm/kvm_host.h

@@ -321,6 +321,7 @@ struct kvm_vcpu_arch {
 	struct kvm_guest_debug_arch external_debug_state;
 
 	struct user_fpsimd_state *host_fpsimd_state;	/* hyp VA */
+	struct task_struct *parent_task;
 
 	struct {
 		/* {Break,watch}point registers */
@@ -737,6 +738,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
+void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu);
 
 static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
 {

arch/arm64/include/asm/kvm_mmu.h

@@ -150,6 +150,8 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
 #include <asm/kvm_pgtable.h>
 #include <asm/stage2_pgtable.h>
 
+int kvm_share_hyp(void *from, void *to);
+void kvm_unshare_hyp(void *from, void *to);
 int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot);
 int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
 			   void __iomem **kaddr,

arch/arm64/include/asm/kvm_pgtable.h

@@ -251,6 +251,27 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt);
 int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
 			enum kvm_pgtable_prot prot);
 
+/**
+ * kvm_pgtable_hyp_unmap() - Remove a mapping from a hypervisor stage-1 page-table.
+ * @pgt:	Page-table structure initialised by kvm_pgtable_hyp_init().
+ * @addr:	Virtual address from which to remove the mapping.
+ * @size:	Size of the mapping.
+ *
+ * The offset of @addr within a page is ignored, @size is rounded-up to
+ * the next page boundary and @phys is rounded-down to the previous page
+ * boundary.
+ *
+ * TLB invalidation is performed for each page-table entry cleared during the
+ * unmapping operation and the reference count for the page-table page
+ * containing the cleared entry is decremented, with unreferenced pages being
+ * freed. The unmapping operation will stop early if it encounters either an
+ * invalid page-table entry or a valid block mapping which maps beyond the range
+ * being unmapped.
+ *
+ * Return: Number of bytes unmapped, which may be 0.
+ */
+u64 kvm_pgtable_hyp_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size);
+
 /**
  * kvm_get_vtcr() - Helper to construct VTCR_EL2
  * @mmfr0:	Sanitized value of SYS_ID_AA64MMFR0_EL1 register.

arch/arm64/kvm/arm.c

@@ -146,7 +146,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	if (ret)
 		return ret;
 
-	ret = create_hyp_mappings(kvm, kvm + 1, PAGE_HYP);
+	ret = kvm_share_hyp(kvm, kvm + 1);
 	if (ret)
 		goto out_free_stage2_pgd;
 
@@ -188,6 +188,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 		}
 	}
 	atomic_set(&kvm->online_vcpus, 0);
+
+	kvm_unshare_hyp(kvm, kvm + 1);
 }
 
 int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
@@ -342,7 +344,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	if (err)
 		return err;
 
-	return create_hyp_mappings(vcpu, vcpu + 1, PAGE_HYP);
+	return kvm_share_hyp(vcpu, vcpu + 1);
 }
 
 void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)

arch/arm64/kvm/fpsimd.c

@@ -14,6 +14,19 @@
 #include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>
 
+void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
+{
+	struct task_struct *p = vcpu->arch.parent_task;
+	struct user_fpsimd_state *fpsimd;
+
+	if (!is_protected_kvm_enabled() || !p)
+		return;
+
+	fpsimd = &p->thread.uw.fpsimd_state;
+	kvm_unshare_hyp(fpsimd, fpsimd + 1);
+	put_task_struct(p);
+}
+
 /*
  * Called on entry to KVM_RUN unless this vcpu previously ran at least
  * once and the most recent prior KVM_RUN for this vcpu was called from
@@ -29,12 +42,27 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 
 	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
 
+	kvm_vcpu_unshare_task_fp(vcpu);
+
 	/* Make sure the host task fpsimd state is visible to hyp: */
-	ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP);
-	if (!ret)
-		vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
+	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
+	if (ret)
+		return ret;
+
+	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
+
+	/*
+	 * We need to keep current's task_struct pinned until its data has been
+	 * unshared with the hypervisor to make sure it is not re-used by the
+	 * kernel and donated to someone else while already shared -- see
+	 * kvm_vcpu_unshare_task_fp() for the matching put_task_struct().
+	 */
+	if (is_protected_kvm_enabled()) {
+		get_task_struct(current);
+		vcpu->arch.parent_task = current;
+	}
 
-	return ret;
+	return 0;
 }
 
 /*

arch/arm64/kvm/hyp/include/nvhe/mem_protect.h

@@ -24,6 +24,11 @@ enum pkvm_page_state {
 	PKVM_PAGE_OWNED			= 0ULL,
 	PKVM_PAGE_SHARED_OWNED		= KVM_PGTABLE_PROT_SW0,
 	PKVM_PAGE_SHARED_BORROWED	= KVM_PGTABLE_PROT_SW1,
+	__PKVM_PAGE_RESERVED		= KVM_PGTABLE_PROT_SW0 |
+					  KVM_PGTABLE_PROT_SW1,
+
+	/* Meta-states which aren't encoded directly in the PTE's SW bits */
+	PKVM_NOPAGE,
 };
 
 #define PKVM_PAGE_STATE_PROT_MASK	(KVM_PGTABLE_PROT_SW0 | KVM_PGTABLE_PROT_SW1)
@@ -50,6 +55,7 @@ extern const u8 pkvm_hyp_id;
 
 int __pkvm_prot_finalize(void);
 int __pkvm_host_share_hyp(u64 pfn);
+int __pkvm_host_unshare_hyp(u64 pfn);
 
 bool addr_is_memory(phys_addr_t phys);
 int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);

arch/arm64/kvm/hyp/nvhe/early_alloc.c

@@ -43,6 +43,9 @@ void *hyp_early_alloc_page(void *arg)
 	return hyp_early_alloc_contig(1);
 }
 
+static void hyp_early_alloc_get_page(void *addr) { }
+static void hyp_early_alloc_put_page(void *addr) { }
+
 void hyp_early_alloc_init(void *virt, unsigned long size)
 {
 	base = cur = (unsigned long)virt;
@@ -51,4 +54,6 @@ void hyp_early_alloc_init(void *virt, unsigned long size)
 	hyp_early_alloc_mm_ops.zalloc_page = hyp_early_alloc_page;
 	hyp_early_alloc_mm_ops.phys_to_virt = hyp_phys_to_virt;
 	hyp_early_alloc_mm_ops.virt_to_phys = hyp_virt_to_phys;
+	hyp_early_alloc_mm_ops.get_page = hyp_early_alloc_get_page;
+	hyp_early_alloc_mm_ops.put_page = hyp_early_alloc_put_page;
 }

arch/arm64/kvm/hyp/nvhe/hyp-main.c

@@ -147,6 +147,13 @@ static void handle___pkvm_host_share_hyp(struct kvm_cpu_context *host_ctxt)
 	cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn);
 }
 
+static void handle___pkvm_host_unshare_hyp(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(u64, pfn, host_ctxt, 1);
+
+	cpu_reg(host_ctxt, 1) = __pkvm_host_unshare_hyp(pfn);
+}
+
 static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(phys_addr_t, phys, host_ctxt, 1);
@@ -184,6 +191,7 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__pkvm_prot_finalize),
 
 	HANDLE_FUNC(__pkvm_host_share_hyp),
+	HANDLE_FUNC(__pkvm_host_unshare_hyp),
 	HANDLE_FUNC(__kvm_adjust_pc),
 	HANDLE_FUNC(__kvm_vcpu_run),
 	HANDLE_FUNC(__kvm_flush_vm_context),