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 8BFBF35E555 for ; Mon, 19 Jan 2026 12:48:19 +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=1768826899; cv=none; b=K4bGPzqRePn/34acv6JwcxLfyj7fpwzomIozFtOZpoV9EFewLwpVsXlGC1XY8Vmc/PCdnA/PedCfg+7N/6wy50kaZ9/zhm8Yn+ZqPmSKDZ5EkCoBvMRVjAC6ZanhhEvTJV1tek7oZ5hZp6mLdqBHiBMVD9TjctbsoB3C5V968d8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768826899; c=relaxed/simple; bh=9YAmtx2N6Hzqu9M4PgAhiSAbJaH9jkJSR2dOrWkXHxU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iIDxL16pnG/k4Inz+wIRrk4ZWsCpd546W+ZgVUkY3l8Ze6GbTfv5+7xYPbmHvLmLLbgegEu/yDEWw3SV5r+VoxeNBdAsh8LduGTqrW2/oBX7cUx4IZQJTRhYapH3obTB9Zvs/t1U1ZWH0JXr7KcDnos36DQMij6uKG77mUVRvHE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Qx2dlUPV; 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="Qx2dlUPV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E35B0C116C6; Mon, 19 Jan 2026 12:48:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768826899; bh=9YAmtx2N6Hzqu9M4PgAhiSAbJaH9jkJSR2dOrWkXHxU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Qx2dlUPVkJMFGSIMIvRsMOy8Nx2HAbZlHdJe43siIAaPLLi2/2yjDH2H7KJ5hiVSc FOud4Y1WCJpe/mXc3kAuw2+ADN6WtB2fbMwkAelwBe9UO0+qkDS63rvMs1yZXYy7JQ ZaYeqmOeruXD8A2KZUoZUquBveIZV6HeWu5p1a/5eII4ds4sb+4thnXGKpyvQKkCs+ /kA/gzsl1Ihf2+slTaB/iznRad/da+VT6+qmuDdYBmmU8b9ZIohy1doEdiifOCtGz5 59C4nJxwNW8t+9fY6tSQrX77z+5VvK6GNYGG8dQ5qpW+1FhzyLN0Y+LfiDPCTnyi0I CgQf90torobZw== 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 28/35] KVM: arm64: Implement the MEM_SHARE hypercall for protected VMs Date: Mon, 19 Jan 2026 12:46:21 +0000 Message-ID: <20260119124629.2563-29-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 Implement the ARM_SMCCC_KVM_FUNC_MEM_SHARE hypercall to allow protected VMs to share memory (e.g. the swiotlb bounce buffers) back to the host. Reviewed-by: Vincent Donnefort 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 | 61 +++++++++++++++++++ 3 files changed, 94 insertions(+) diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index 5e6cdafcdd69..42fd60c5cfc9 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -35,6 +35,7 @@ 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_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 914b373cfb56..7535a45565f4 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -967,6 +967,38 @@ int __pkvm_host_share_hyp(u64 pfn) return ret; } +int __pkvm_guest_share_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_OWNED) + goto unlock; + if (__host_check_page_state_range(phys, PAGE_SIZE, PKVM_NOPAGE)) + goto unlock; + + ret = 0; + WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys, + pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED), + &vcpu->vcpu.arch.pkvm_memcache, 0)); + WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_BORROWED)); +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 64171e04ea82..4133556560d9 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -937,6 +937,58 @@ int __pkvm_finalize_teardown_vm(pkvm_handle_t handle) hyp_spin_unlock(&vm_table_lock); return err; } + +static u64 __pkvm_memshare_page_req(struct kvm_vcpu *vcpu, u64 ipa) +{ + u64 elr; + + /* Fake up a data abort (level 3 translation fault on write) */ + vcpu->arch.fault.esr_el2 = (ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT) | + ESR_ELx_WNR | ESR_ELx_FSC_FAULT | + FIELD_PREP(ESR_ELx_FSC_LEVEL, 3); + + /* Shuffle the IPA around into the HPFAR */ + vcpu->arch.fault.hpfar_el2 = (HPFAR_EL2_NS | (ipa >> 8)) & HPFAR_MASK; + + /* This is a virtual address. 0's good. Let's go with 0. */ + vcpu->arch.fault.far_el2 = 0; + + /* Rewind the ELR so we return to the HVC once the IPA is mapped */ + elr = read_sysreg(elr_el2); + elr -= 4; + write_sysreg(elr, elr_el2); + + return ARM_EXCEPTION_TRAP; +} + +static bool pkvm_memshare_call(u64 *ret, struct kvm_vcpu *vcpu, u64 *exit_code) +{ + struct pkvm_hyp_vcpu *hyp_vcpu; + u64 ipa = smccc_get_arg1(vcpu); + + if (!PAGE_ALIGNED(ipa)) + goto out_guest; + + hyp_vcpu = container_of(vcpu, struct pkvm_hyp_vcpu, vcpu); + switch (__pkvm_guest_share_host(hyp_vcpu, hyp_phys_to_pfn(ipa))) { + case 0: + ret[0] = SMCCC_RET_SUCCESS; + goto out_guest; + case -ENOENT: + /* + * Convert the exception into a data abort so that the page + * being shared is mapped into the guest next time. + */ + *exit_code = __pkvm_memshare_page_req(vcpu, ipa); + goto out_host; + } + +out_guest: + return true; +out_host: + return false; +} + /* * Handler for protected VM HVC calls. * @@ -953,6 +1005,7 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code) case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID: 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); break; case ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID: if (smccc_get_arg1(vcpu) || @@ -963,6 +1016,14 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code) val[0] = PAGE_SIZE; break; + case ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID: + if (smccc_get_arg2(vcpu) || + smccc_get_arg3(vcpu)) { + break; + } + + handled = pkvm_memshare_call(val, vcpu, exit_code); + break; default: /* Punt everything else back to the host, for now. */ handled = false; -- 2.52.0.457.g6b5491de43-goog