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 DDD8D305E32 for ; Mon, 5 Jan 2026 15:51:07 +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=1767628267; cv=none; b=hzpyis/tbBq6QvHKuA8XQ3NcAZiTpqDtQHiHwqAV8TB7ImX8VSOdOc77w3Z0YGjFTeC6zNM7jZETO554k6YFrgR+bXRljP3pmuluxTs+OAOZnPJphzprbJZtMml5FUKVkcMQnsZ+O/c6pq/iNmpCVcBMfGygrbs6SnCLTDm2i0k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767628267; c=relaxed/simple; bh=BmsYgqIT3uKN2zRXoz1a0bZTuLRzk92Jv5uTqm+wEjk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Zc6/RmVN2McEcgK/YDSB8YEu2dK6hSz0Z5fBj+jIbMADbIfXfKy6h2ixgKaSu15u5O5I+xwtHIpbihkJ3cLdOHKXV741pmACHnQtu/OiG7jJI3tW2mnJrlRn/OaVtErpqo/ofdE0IzWQFp7IaSk6/HeeUr1JoeI+/4lFjt9vzfo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=faDll1Wb; 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="faDll1Wb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37BBBC19421; Mon, 5 Jan 2026 15:51:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767628267; bh=BmsYgqIT3uKN2zRXoz1a0bZTuLRzk92Jv5uTqm+wEjk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=faDll1WbHW4Yz/l01C1KlR3cln6HGbtAlXXtchRUcWy3maw94CtldBVIIT3qj4RRi h34KaFarwFQ/bCJGA+fB/Ck8YBknvm8uS9UQ/gVooevV67feSRvJFUbSFUh8QHdJiZ RmppDk+xovNHeimfcRdA0yMJtjhiEembpTZDTRfbfsBR86aZRciJknKo/jbr1TNHis D3s2VuRnZar4dr1SdFmubTZHBVUb+zcg1FgqQ/MkpXvMEioT3EkgkMGrWUrAZjN9VC W4n/zpaNhNmEpapAdejSItV2tCfwV4VJzzeTqHObqBmoeWZTdGquOxHfuoUACUlUiN 1uxuRaPubmaqQ== 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 25/30] KVM: arm64: Implement the MEM_UNSHARE hypercall for protected VMs Date: Mon, 5 Jan 2026 15:49:33 +0000 Message-ID: <20260105154939.11041-26-will@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260105154939.11041-1-will@kernel.org> References: <20260105154939.11041-1-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 Implement the ARM_SMCCC_KVM_FUNC_MEM_UNSHARE hypercall to allow protected VMs to unshare memory that was previously shared with the host using the ARM_SMCCC_KVM_FUNC_MEM_SHARE hypercall. Signed-off-by: Will Deacon --- arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 + arch/arm64/kvm/hyp/nvhe/mem_protect.c | 32 +++++++++++++++++++ arch/arm64/kvm/hyp/nvhe/pkvm.c | 22 +++++++++++++ 3 files changed, 55 insertions(+) diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index 42fd60c5cfc9..e41a128b0854 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -36,6 +36,7 @@ extern unsigned long hyp_nr_cpus; int __pkvm_prot_finalize(void); int __pkvm_host_share_hyp(u64 pfn); int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn); +int __pkvm_guest_unshare_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn); int __pkvm_host_unshare_hyp(u64 pfn); int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages); int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages); diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 365c769c82a4..c1600b88c316 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -920,6 +920,38 @@ int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn) return ret; } +int __pkvm_guest_unshare_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn) +{ + struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu); + u64 phys, ipa = hyp_pfn_to_phys(gfn); + kvm_pte_t pte; + int ret; + + host_lock_component(); + guest_lock_component(vm); + + ret = get_valid_guest_pte(vm, ipa, &pte, &phys); + if (ret) + goto unlock; + + ret = -EPERM; + if (pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte)) != PKVM_PAGE_SHARED_OWNED) + goto unlock; + if (__host_check_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_BORROWED)) + goto unlock; + + ret = 0; + 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_unshare_hyp(u64 pfn) { u64 phys = hyp_pfn_to_phys(pfn); diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index d8afa2b98542..2890328f4a78 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -988,6 +988,19 @@ static bool pkvm_memshare_call(u64 *ret, struct kvm_vcpu *vcpu, u64 *exit_code) return false; } +static void pkvm_memunshare_call(u64 *ret, struct kvm_vcpu *vcpu) +{ + struct pkvm_hyp_vcpu *hyp_vcpu; + u64 ipa = smccc_get_arg1(vcpu); + + if (!PAGE_ALIGNED(ipa)) + return; + + hyp_vcpu = container_of(vcpu, struct pkvm_hyp_vcpu, vcpu); + if (!__pkvm_guest_unshare_host(hyp_vcpu, hyp_phys_to_pfn(ipa))) + ret[0] = SMCCC_RET_SUCCESS; +} + /* * Handler for protected VM HVC calls. * @@ -1005,6 +1018,7 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code) val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES); val[0] |= BIT(ARM_SMCCC_KVM_FUNC_HYP_MEMINFO); val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MEM_SHARE); + val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MEM_UNSHARE); break; case ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID: if (smccc_get_arg1(vcpu) || @@ -1023,6 +1037,14 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code) handled = pkvm_memshare_call(val, vcpu, exit_code); break; + case ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID: + if (smccc_get_arg2(vcpu) || + smccc_get_arg3(vcpu)) { + break; + } + + pkvm_memunshare_call(val, vcpu); + break; default: /* Punt everything else back to the host, for now. */ handled = false; -- 2.52.0.351.gbe84eed79e-goog