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Peter Anvin" Subject: [PATCH v4 02/24] coco/tdx-host: Introduce a "tdx_host" device Date: Thu, 12 Feb 2026 06:35:05 -0800 Message-ID: <20260212143606.534586-3-chao.gao@intel.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260212143606.534586-1-chao.gao@intel.com> References: <20260212143606.534586-1-chao.gao@intel.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit TDX depends on a platform firmware module that is invoked via instructions similar to vmenter (i.e. enter into a new privileged "root-mode" context to manage private memory and private device mechanisms). It is a software construct that depends on the CPU vmxon state to enable invocation of TDX-module ABIs. Unlike other Trusted Execution Environment (TEE) platform implementations that employ a firmware module running on a PCI device with an MMIO mailbox for communication, TDX has no hardware device to point to as the TEE Secure Manager (TSM). Create a virtual device not only to align with other implementations but also to make it easier to - expose metadata (e.g., TDX module version, seamldr version etc) to the userspace as device attributes - implement firmware uploader APIs which are tied to a device. This is needed to support TDX module runtime updates - enable TDX Connect which will share a common infrastructure with other platform implementations. In the TDX Connect context, every architecture has a TSM, represented by a PCIe or virtual device. The new "tdx_host" device will serve the TSM role. A faux device is used as for TDX because the TDX module is singular within the system and lacks associated platform resources. Using a faux device eliminates the need to create a stub bus. The call to tdx_get_sysinfo() ensures that the TDX Module is ready to provide services. Note that AMD has a PCI device for the PSP for SEV and ARM CCA will likely have a faux device [1]. Co-developed-by: Xu Yilun Signed-off-by: Xu Yilun Signed-off-by: Dan Williams Signed-off-by: Chao Gao Reviewed-by: Jonathan Cameron Reviewed-by: Tony Lindgren Reviewed-by: Xu Yilun Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh/ # [1] --- v3: - add Jonathan's reviewed-by - add tdx_get_sysinfo() in module_init() to ensure the TDX Module is up and running. - note in the changelog that both AMD and ARM have devices for coco --- arch/x86/virt/vmx/tdx/tdx.c | 2 +- drivers/virt/coco/Kconfig | 2 ++ drivers/virt/coco/Makefile | 1 + drivers/virt/coco/tdx-host/Kconfig | 10 +++++++ drivers/virt/coco/tdx-host/Makefile | 1 + drivers/virt/coco/tdx-host/tdx-host.c | 43 +++++++++++++++++++++++++++ 6 files changed, 58 insertions(+), 1 deletion(-) create mode 100644 drivers/virt/coco/tdx-host/Kconfig create mode 100644 drivers/virt/coco/tdx-host/Makefile create mode 100644 drivers/virt/coco/tdx-host/tdx-host.c diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index ddcc1a8c743f..b65b2a609e81 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -1435,7 +1435,7 @@ const struct tdx_sys_info *tdx_get_sysinfo(void) return p; } -EXPORT_SYMBOL_FOR_KVM(tdx_get_sysinfo); +EXPORT_SYMBOL_FOR_MODULES(tdx_get_sysinfo, "kvm-intel,tdx-host"); u32 tdx_get_nr_guest_keyids(void) { diff --git a/drivers/virt/coco/Kconfig b/drivers/virt/coco/Kconfig index df1cfaf26c65..f7691f64fbe3 100644 --- a/drivers/virt/coco/Kconfig +++ b/drivers/virt/coco/Kconfig @@ -17,5 +17,7 @@ source "drivers/virt/coco/arm-cca-guest/Kconfig" source "drivers/virt/coco/guest/Kconfig" endif +source "drivers/virt/coco/tdx-host/Kconfig" + config TSM bool diff --git a/drivers/virt/coco/Makefile b/drivers/virt/coco/Makefile index cb52021912b3..b323b0ae4f82 100644 --- a/drivers/virt/coco/Makefile +++ b/drivers/virt/coco/Makefile @@ -6,6 +6,7 @@ obj-$(CONFIG_EFI_SECRET) += efi_secret/ obj-$(CONFIG_ARM_PKVM_GUEST) += pkvm-guest/ obj-$(CONFIG_SEV_GUEST) += sev-guest/ obj-$(CONFIG_INTEL_TDX_GUEST) += tdx-guest/ +obj-$(CONFIG_INTEL_TDX_HOST) += tdx-host/ obj-$(CONFIG_ARM_CCA_GUEST) += arm-cca-guest/ obj-$(CONFIG_TSM) += tsm-core.o obj-$(CONFIG_TSM_GUEST) += guest/ diff --git a/drivers/virt/coco/tdx-host/Kconfig b/drivers/virt/coco/tdx-host/Kconfig new file mode 100644 index 000000000000..e58bad148a35 --- /dev/null +++ b/drivers/virt/coco/tdx-host/Kconfig @@ -0,0 +1,10 @@ +config TDX_HOST_SERVICES + tristate "TDX Host Services Driver" + depends on INTEL_TDX_HOST + default m + help + Enable access to TDX host services like module update and + extensions (e.g. TDX Connect). + + Say y or m if enabling support for confidential virtual machine + support (CONFIG_INTEL_TDX_HOST). The module is called tdx_host.ko diff --git a/drivers/virt/coco/tdx-host/Makefile b/drivers/virt/coco/tdx-host/Makefile new file mode 100644 index 000000000000..e61e749a8dff --- /dev/null +++ b/drivers/virt/coco/tdx-host/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_TDX_HOST_SERVICES) += tdx-host.o diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c new file mode 100644 index 000000000000..c77885392b09 --- /dev/null +++ b/drivers/virt/coco/tdx-host/tdx-host.c @@ -0,0 +1,43 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * TDX host user interface driver + * + * Copyright (C) 2025 Intel Corporation + */ + +#include +#include +#include + +#include +#include + +static const struct x86_cpu_id tdx_host_ids[] = { + X86_MATCH_FEATURE(X86_FEATURE_TDX_HOST_PLATFORM, NULL), + {} +}; +MODULE_DEVICE_TABLE(x86cpu, tdx_host_ids); + +static struct faux_device *fdev; + +static int __init tdx_host_init(void) +{ + if (!x86_match_cpu(tdx_host_ids) || !tdx_get_sysinfo()) + return -ENODEV; + + fdev = faux_device_create(KBUILD_MODNAME, NULL, NULL); + if (!fdev) + return -ENODEV; + + return 0; +} +module_init(tdx_host_init); + +static void __exit tdx_host_exit(void) +{ + faux_device_destroy(fdev); +} +module_exit(tdx_host_exit); + +MODULE_DESCRIPTION("TDX Host Services"); +MODULE_LICENSE("GPL"); -- 2.47.3