From: Will Deacon Date: Mon, 30 Mar 2026 14:48:16 +0000 (+0100) Subject: KVM: arm64: Introduce __pkvm_reclaim_dying_guest_page() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0bf5f4d400cd11ab86b25a56b101726e35f3e7cb;p=thirdparty%2Fkernel%2Fstable.git KVM: arm64: Introduce __pkvm_reclaim_dying_guest_page() To enable reclaim of pages from a protected VM during teardown, introduce a new hypercall to reclaim a single page from a protected guest that is in the dying state. Since the EL2 code is non-preemptible, the new hypercall deliberately acts on a single page at a time so as to allow EL1 to reschedule frequently during the teardown operation. Reviewed-by: Vincent Donnefort Tested-by: Fuad Tabba Tested-by: Mostafa Saleh Co-developed-by: Quentin Perret Signed-off-by: Quentin Perret Signed-off-by: Will Deacon Link: https://patch.msgid.link/20260330144841.26181-16-will@kernel.org Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index dfc6625c8269..b6df8f64d573 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -90,6 +90,7 @@ enum __kvm_host_smccc_func { __KVM_HOST_SMCCC_FUNC___pkvm_unreserve_vm, __KVM_HOST_SMCCC_FUNC___pkvm_init_vm, __KVM_HOST_SMCCC_FUNC___pkvm_init_vcpu, + __KVM_HOST_SMCCC_FUNC___pkvm_reclaim_dying_guest_page, __KVM_HOST_SMCCC_FUNC___pkvm_start_teardown_vm, __KVM_HOST_SMCCC_FUNC___pkvm_finalize_teardown_vm, __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_load, diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index 7061b0be340a..29f81a1d9e1f 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -40,6 +40,7 @@ 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_reclaim_page_guest(u64 gfn, struct pkvm_hyp_vm *vm); 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/include/nvhe/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h index 04c7ca703014..506831804f64 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h @@ -74,6 +74,7 @@ int __pkvm_init_vm(struct kvm *host_kvm, unsigned long vm_hva, int __pkvm_init_vcpu(pkvm_handle_t handle, struct kvm_vcpu *host_vcpu, unsigned long vcpu_hva); +int __pkvm_reclaim_dying_guest_page(pkvm_handle_t handle, u64 gfn); int __pkvm_start_teardown_vm(pkvm_handle_t handle); int __pkvm_finalize_teardown_vm(pkvm_handle_t handle); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 970656318cf2..7294c94f9296 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -573,6 +573,14 @@ static void handle___pkvm_init_vcpu(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 1) = __pkvm_init_vcpu(handle, host_vcpu, vcpu_hva); } +static void handle___pkvm_reclaim_dying_guest_page(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1); + DECLARE_REG(u64, gfn, host_ctxt, 2); + + cpu_reg(host_ctxt, 1) = __pkvm_reclaim_dying_guest_page(handle, gfn); +} + static void handle___pkvm_start_teardown_vm(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1); @@ -626,6 +634,7 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__pkvm_unreserve_vm), HANDLE_FUNC(__pkvm_init_vm), HANDLE_FUNC(__pkvm_init_vcpu), + HANDLE_FUNC(__pkvm_reclaim_dying_guest_page), HANDLE_FUNC(__pkvm_start_teardown_vm), HANDLE_FUNC(__pkvm_finalize_teardown_vm), HANDLE_FUNC(__pkvm_vcpu_load), diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 03e6fa124253..ca266a4d9d50 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -738,6 +738,32 @@ static int __guest_check_page_state_range(struct pkvm_hyp_vm *vm, u64 addr, return check_page_state_range(&vm->pgt, addr, size, &d); } +static int get_valid_guest_pte(struct pkvm_hyp_vm *vm, u64 ipa, kvm_pte_t *ptep, u64 *physp) +{ + kvm_pte_t pte; + u64 phys; + s8 level; + int ret; + + ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level); + if (ret) + return ret; + if (!kvm_pte_valid(pte)) + return -ENOENT; + if (level != KVM_PGTABLE_LAST_LEVEL) + return -E2BIG; + + phys = kvm_pte_to_phys(pte); + ret = check_range_allowed_memory(phys, phys + PAGE_SIZE); + if (WARN_ON(ret)) + return ret; + + *ptep = pte; + *physp = phys; + + return 0; +} + int __pkvm_host_share_hyp(u64 pfn) { u64 phys = hyp_pfn_to_phys(pfn); @@ -971,6 +997,59 @@ static int __guest_check_transition_size(u64 phys, u64 ipa, u64 nr_pages, u64 *s return 0; } +static void hyp_poison_page(phys_addr_t phys) +{ + void *addr = hyp_fixmap_map(phys); + + memset(addr, 0, PAGE_SIZE); + /* + * Prefer kvm_flush_dcache_to_poc() over __clean_dcache_guest_page() + * here as the latter may elide the CMO under the assumption that FWB + * will be enabled on CPUs that support it. This is incorrect for the + * host stage-2 and would otherwise lead to a malicious host potentially + * being able to read the contents of newly reclaimed guest pages. + */ + kvm_flush_dcache_to_poc(addr, PAGE_SIZE); + hyp_fixmap_unmap(); +} + +int __pkvm_host_reclaim_page_guest(u64 gfn, struct pkvm_hyp_vm *vm) +{ + u64 ipa = hyp_pfn_to_phys(gfn); + kvm_pte_t pte; + u64 phys; + int ret; + + host_lock_component(); + guest_lock_component(vm); + + ret = get_valid_guest_pte(vm, ipa, &pte, &phys); + if (ret) + goto unlock; + + switch (guest_get_page_state(pte, ipa)) { + case PKVM_PAGE_OWNED: + WARN_ON(__host_check_page_state_range(phys, PAGE_SIZE, PKVM_NOPAGE)); + hyp_poison_page(phys); + break; + case PKVM_PAGE_SHARED_OWNED: + WARN_ON(__host_check_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_BORROWED)); + break; + default: + ret = -EPERM; + goto unlock; + } + + WARN_ON(kvm_pgtable_stage2_unmap(&vm->pgt, ipa, PAGE_SIZE)); + WARN_ON(host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_HOST)); + +unlock: + guest_unlock_component(vm); + host_unlock_component(); + + return ret; +} + 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); diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 61e69e24656a..092e9d0e55ac 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -868,6 +868,20 @@ teardown_donated_memory(struct kvm_hyp_memcache *mc, void *addr, size_t size) unmap_donated_memory_noclear(addr, size); } +int __pkvm_reclaim_dying_guest_page(pkvm_handle_t handle, u64 gfn) +{ + struct pkvm_hyp_vm *hyp_vm; + int ret = -EINVAL; + + hyp_spin_lock(&vm_table_lock); + hyp_vm = get_vm_by_handle(handle); + if (hyp_vm && hyp_vm->kvm.arch.pkvm.is_dying) + ret = __pkvm_host_reclaim_page_guest(gfn, hyp_vm); + hyp_spin_unlock(&vm_table_lock); + + return ret; +} + int __pkvm_start_teardown_vm(pkvm_handle_t handle) { struct pkvm_hyp_vm *hyp_vm;