From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D9E635E555 for ; Mon, 19 Jan 2026 12:48:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768826887; cv=none; b=LntkZlLHiN7L0yIeBsKavhX0toAeIKVAUww5JV7jRUEDRJB/QLJVI0hB3uqKI4BM2t/OFlxgi1WS9l0ic042Bv3XeP2S4myYkQGDUXXvfqTwFqZ7fP/M15DhE09GbUCuMLuPj9FyqqbRyR8jN1jHtsC0clzxSdas/KBZ+5cN6dk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768826887; c=relaxed/simple; bh=GpcJQTp33npVBpg5/HBuV7HtkRiZ8dpEfkojHzLrxio=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=vGMyVgZHENtsCPemJiAaVrqSFsX688zLr9bVTotHV78L7Jvx1Qjstzx9P8P06Jdp4cIsGFzhUwWysFONLsbsgRk8J6v1t55ab6j9aCTykKNTQkeF9rb7sdUxOwnrb5CvFsa3xJwfNiao0TvIuROlRiqFmfebrDjlz9Kb0iZsiBM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=vGhZ2owo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="vGhZ2owo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9987BC19424; Mon, 19 Jan 2026 12:48:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768826887; bh=GpcJQTp33npVBpg5/HBuV7HtkRiZ8dpEfkojHzLrxio=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vGhZ2owoBxlKN1ximzep3m6vJQ2O4A8pBN1Er2A2nULoEIHtKqlAvNBC3IZSovm8I weVRf/4DMGtyTxC7NjiUrplv4fpChv4rTDDSGvhmwFgi3IpWddIREdi49lRddGSL4Z GeXeXZgRJlijt/Av7ISrq/avjVKeW/WJOlxdmmtnkByJQzNsx0JUk2Eu2d8/FWCsHO O2l7UETkLCxhza7Sv8plsqvUsywyynnYZjeMh2aQBBafhkBZD757XbnB1rWxKmz8xF Gqt9jiS8ShWPskg3SNE7sPZ/3jzv9/UWqBIk/C5excH6XN1ghQgMIDxBCQSbZu7yxa EM8EwMsOpP6VA== From: Will Deacon To: kvmarm@lists.linux.dev Cc: linux-arm-kernel@lists.infradead.org, Will Deacon , Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Quentin Perret , Fuad Tabba , Vincent Donnefort , Mostafa Saleh Subject: [PATCH v2 24/35] KVM: arm64: Introduce hypercall to force reclaim of a protected page Date: Mon, 19 Jan 2026 12:46:17 +0000 Message-ID: <20260119124629.2563-25-will@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260119124629.2563-1-will@kernel.org> References: <20260119124629.2563-1-will@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce a new hypercall, __pkvm_force_reclaim_guest_page(), to allow the host to forcefully reclaim a physical page that was previous donated to a protected guest. This results in the page being zeroed and the previous guest mapping being poisoned so that new pages cannot be subsequently donated at the same IPA. Signed-off-by: Will Deacon --- arch/arm64/include/asm/kvm_asm.h | 1 + arch/arm64/include/asm/kvm_pgtable.h | 6 + arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 + arch/arm64/kvm/hyp/include/nvhe/memory.h | 6 + arch/arm64/kvm/hyp/include/nvhe/pkvm.h | 1 + arch/arm64/kvm/hyp/nvhe/hyp-main.c | 8 ++ arch/arm64/kvm/hyp/nvhe/mem_protect.c | 127 +++++++++++++++++- arch/arm64/kvm/hyp/nvhe/pkvm.c | 4 +- 8 files changed, 152 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 2e7e8e7771f6..39e4e588ca4f 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_force_reclaim_guest_page, __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, diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index eb2a6258d83d..4c069f875a85 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -114,6 +114,12 @@ enum kvm_invalid_pte_type { * ownership. */ KVM_HOST_INVALID_PTE_TYPE_DONATION, + + /* + * The page has been forcefully reclaimed from the guest by the + * host. + */ + KVM_GUEST_INVALID_PTE_TYPE_POISONED, }; static inline bool kvm_pte_valid(kvm_pte_t pte) diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index cde38a556049..f27b037abaf3 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -41,6 +41,7 @@ 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_force_reclaim_page_guest(phys_addr_t phys); 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); diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h index dee1a406b0c2..4cedb720c75d 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h @@ -30,6 +30,12 @@ enum pkvm_page_state { * struct hyp_page. */ PKVM_NOPAGE = BIT(0) | BIT(1), + + /* + * 'Meta-states' which aren't encoded directly in the PTE's SW bits (or + * the hyp_vmemmap entry for the host) + */ + PKVM_POISON = BIT(2), }; #define PKVM_PAGE_STATE_MASK (BIT(0) | BIT(1)) diff --git a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h index 506831804f64..a5a7bb453f3e 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h @@ -78,6 +78,7 @@ 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); +struct pkvm_hyp_vm *get_vm_by_handle(pkvm_handle_t handle); struct pkvm_hyp_vcpu *pkvm_load_hyp_vcpu(pkvm_handle_t handle, unsigned int vcpu_idx); void pkvm_put_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index f43c50ae2d81..e68b5d24bdad 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -570,6 +570,13 @@ 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_force_reclaim_guest_page(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(phys_addr_t, phys, host_ctxt, 1); + + cpu_reg(host_ctxt, 1) = __pkvm_host_force_reclaim_page_guest(phys); +} + static void handle___pkvm_reclaim_dying_guest_page(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1); @@ -631,6 +638,7 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__pkvm_unreserve_vm), HANDLE_FUNC(__pkvm_init_vm), HANDLE_FUNC(__pkvm_init_vcpu), + HANDLE_FUNC(__pkvm_force_reclaim_guest_page), HANDLE_FUNC(__pkvm_reclaim_dying_guest_page), HANDLE_FUNC(__pkvm_start_teardown_vm), HANDLE_FUNC(__pkvm_finalize_teardown_vm), diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index f4638fe9d77a..49b309b8d7d2 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -613,6 +613,35 @@ static u64 host_stage2_encode_gfn_meta(struct pkvm_hyp_vm *vm, u64 gfn) FIELD_PREP(KVM_HOST_PTE_OWNER_GUEST_GFN_MASK, gfn); } +static int host_stage2_decode_gfn_meta(kvm_pte_t pte, struct pkvm_hyp_vm **vm, + u64 *gfn) +{ + pkvm_handle_t handle; + u64 meta; + + if (WARN_ON(kvm_pte_valid(pte))) + return -EINVAL; + + if (FIELD_GET(KVM_INVALID_PTE_TYPE_MASK, pte) != + KVM_HOST_INVALID_PTE_TYPE_DONATION) { + return -EINVAL; + } + + if (FIELD_GET(KVM_HOST_DONATION_PTE_OWNER_MASK, pte) != PKVM_ID_GUEST) + return -EPERM; + + meta = FIELD_GET(KVM_HOST_DONATION_PTE_EXTRA_MASK, pte); + handle = FIELD_GET(KVM_HOST_PTE_OWNER_GUEST_HANDLE_MASK, meta); + *vm = get_vm_by_handle(handle); + if (!*vm) { + /* We probably raced with teardown; try again */ + return -EAGAIN; + } + + *gfn = FIELD_GET(KVM_HOST_PTE_OWNER_GUEST_GFN_MASK, meta); + return 0; +} + static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot) { /* @@ -809,8 +838,20 @@ static int __hyp_check_page_state_range(phys_addr_t phys, u64 size, enum pkvm_pa return 0; } +static bool guest_pte_is_poisoned(kvm_pte_t pte) +{ + if (kvm_pte_valid(pte)) + return false; + + return FIELD_GET(KVM_INVALID_PTE_TYPE_MASK, pte) == + KVM_GUEST_INVALID_PTE_TYPE_POISONED; +} + static enum pkvm_page_state guest_get_page_state(kvm_pte_t pte, u64 addr) { + if (guest_pte_is_poisoned(pte)) + return PKVM_POISON; + if (!kvm_pte_valid(pte)) return PKVM_NOPAGE; @@ -839,6 +880,8 @@ static int get_valid_guest_pte(struct pkvm_hyp_vm *vm, u64 ipa, kvm_pte_t *ptep, ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level); if (ret) return ret; + if (guest_pte_is_poisoned(pte)) + return -EHWPOISON; if (!kvm_pte_valid(pte)) return -ENOENT; if (level != KVM_PGTABLE_LAST_LEVEL) @@ -1104,6 +1147,84 @@ static void hyp_poison_page(phys_addr_t phys) hyp_fixmap_unmap(); } +static int host_stage2_get_guest_info(phys_addr_t phys, struct pkvm_hyp_vm **vm, + u64 *gfn) +{ + enum pkvm_page_state state; + kvm_pte_t pte; + s8 level; + int ret; + + if (!addr_is_memory(phys)) + return -EFAULT; + + state = get_host_state(hyp_phys_to_page(phys)); + switch (state) { + case PKVM_PAGE_OWNED: + case PKVM_PAGE_SHARED_OWNED: + case PKVM_PAGE_SHARED_BORROWED: + /* The access should no longer fault; try again. */ + return -EAGAIN; + case PKVM_NOPAGE: + break; + default: + return -EPERM; + } + + ret = kvm_pgtable_get_leaf(&host_mmu.pgt, phys, &pte, &level); + if (ret) + return ret; + + if (WARN_ON(level != KVM_PGTABLE_LAST_LEVEL)) + return -EINVAL; + + return host_stage2_decode_gfn_meta(pte, vm, gfn); +} + +int __pkvm_host_force_reclaim_page_guest(phys_addr_t phys) +{ + struct pkvm_hyp_vm *vm; + u64 gfn, ipa, pa; + kvm_pte_t pte; + int ret; + + hyp_spin_lock(&vm_table_lock); + host_lock_component(); + + ret = host_stage2_get_guest_info(phys, &vm, &gfn); + if (ret) + goto unlock_host; + + ipa = hyp_pfn_to_phys(gfn); + guest_lock_component(vm); + ret = get_valid_guest_pte(vm, ipa, &pte, &pa); + if (ret) + goto unlock_guest; + + WARN_ON(pa != phys); + if (guest_get_page_state(pte, ipa) != PKVM_PAGE_OWNED) { + ret = -EPERM; + goto unlock_guest; + } + + /* We really shouldn't be allocating, so don't pass a memcache */ + ret = kvm_pgtable_stage2_annotate(&vm->pgt, ipa, PAGE_SIZE, NULL, + KVM_GUEST_INVALID_PTE_TYPE_POISONED, + 0); + if (ret) + goto unlock_guest; + + hyp_poison_page(phys); + WARN_ON(host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_HOST)); +unlock_guest: + guest_unlock_component(vm); +unlock_host: + host_unlock_component(); + hyp_spin_unlock(&vm_table_lock); + + return ret; +} + int __pkvm_host_reclaim_page_guest(u64 gfn, struct pkvm_hyp_vm *vm) { u64 ipa = hyp_pfn_to_phys(gfn); @@ -1138,7 +1259,11 @@ int __pkvm_host_reclaim_page_guest(u64 gfn, struct pkvm_hyp_vm *vm) guest_unlock_component(vm); host_unlock_component(); - return ret; + /* + * -EHWPOISON implies that the page was forcefully reclaimed already + * so return success for the GUP pin to be dropped. + */ + return ret && ret != -EHWPOISON ? ret : 0; } int __pkvm_host_donate_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu) diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index c5772417372d..2836c68c1ea5 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -231,10 +231,12 @@ void pkvm_hyp_vm_table_init(void *tbl) /* * Return the hyp vm structure corresponding to the handle. */ -static struct pkvm_hyp_vm *get_vm_by_handle(pkvm_handle_t handle) +struct pkvm_hyp_vm *get_vm_by_handle(pkvm_handle_t handle) { unsigned int idx = vm_handle_to_idx(handle); + hyp_assert_lock_held(&vm_table_lock); + if (unlikely(idx >= KVM_MAX_PVMS)) return NULL; -- 2.52.0.457.g6b5491de43-goog