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Peter Anvin" Subject: [PATCH v10 10/25] coco/tdx-host: Expose P-SEAMLDR information via sysfs Date: Wed, 20 May 2026 06:38:13 -0700 Message-ID: <20260520133909.409394-11-chao.gao@intel.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260520133909.409394-1-chao.gao@intel.com> References: <20260520133909.409394-1-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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit TDX module updates require userspace to select the appropriate module to load. Expose necessary information to facilitate this decision. Two values are needed: - P-SEAMLDR version: for compatibility checks between TDX module and P-SEAMLDR - num_remaining_updates: indicates how many updates can be performed Expose them as tdx-host device attributes. Make seamldr attributes visible only when the update feature is supported, as that's their sole purpose. Note that the underlying P-SEAMLDR attributes are available regardless of update support; this only restricts their visibility in Linux. Signed-off-by: Chao Gao Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: Dave Hansen --- v10: - Describe the P-SEAMLDR version by referring to the TDX module version instead of copying the text [Dave] - add a comment for DEVICE_ATTR_ADMIN_RO() [Dave] - Avoid the tertiary operator [Dave] --- .../ABI/testing/sysfs-devices-faux-tdx-host | 21 ++++++ arch/x86/include/asm/tdx.h | 6 ++ drivers/virt/coco/tdx-host/tdx-host.c | 72 ++++++++++++++++++- 3 files changed, 98 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host index 47d73cb89f1e..69b4cfc99d87 100644 --- a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host +++ b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host @@ -3,3 +3,24 @@ Contact: linux-coco@lists.linux.dev Description: (RO) Report the version of the loaded TDX module. Formatted as "major.minor.update". Used by TDX module update tooling. Example: "1.2.03". + +What: /sys/devices/faux/tdx_host/seamldr_version +Contact: linux-coco@lists.linux.dev +Description: (RO) Report the version of the loaded P-SEAMLDR. + Formatted as a TDX module version. Used by TDX module + update tooling. + +What: /sys/devices/faux/tdx_host/num_remaining_updates +Contact: linux-coco@lists.linux.dev +Description: (RO) Report the number of remaining updates. TDX maintains a + log about each TDX module that has been loaded. This log has + a finite size, which limits the number of TDX module updates + that can be performed. + + After each successful update, the number reduces by one. Once it + reaches zero, further updates will fail until next reboot. The + number is always zero if the P-SEAMLDR doesn't support updates. + + See Intel® Trust Domain Extensions - SEAM Loader (SEAMLDR) + Interface Specification, Chapter "SEAMLDR_INFO" and Chapter + "SEAMLDR.INSTALL" for more information. diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index b7f4396b5cc5..27376db7ddac 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -110,6 +110,12 @@ void tdx_init(void); const char *tdx_dump_mce_info(struct mce *m); const struct tdx_sys_info *tdx_get_sysinfo(void); +static inline bool tdx_supports_runtime_update(const struct tdx_sys_info *sysinfo) +{ + /* To be enabled when kernel is ready. */ + return false; +} + int tdx_guest_keyid_alloc(void); u32 tdx_get_nr_guest_keyids(void); void tdx_guest_keyid_free(unsigned int keyid); diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c index ef117a836b3a..2997311f72fa 100644 --- a/drivers/virt/coco/tdx-host/tdx-host.c +++ b/drivers/virt/coco/tdx-host/tdx-host.c @@ -11,6 +11,7 @@ #include #include +#include #include static const struct x86_cpu_id tdx_host_ids[] = { @@ -40,7 +41,76 @@ static struct attribute *tdx_host_attrs[] = { &dev_attr_version.attr, NULL, }; -ATTRIBUTE_GROUPS(tdx_host); + +static const struct attribute_group tdx_host_group = { + .attrs = tdx_host_attrs, +}; + +static ssize_t seamldr_version_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct seamldr_info info; + int ret; + + ret = seamldr_get_info(&info); + if (ret) + return ret; + + return sysfs_emit(buf, TDX_VERSION_FMT "\n", info.major_version, + info.minor_version, + info.update_version); +} + +static ssize_t num_remaining_updates_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct seamldr_info info; + int ret; + + ret = seamldr_get_info(&info); + if (ret) + return ret; + + return sysfs_emit(buf, "%u\n", info.num_remaining_updates); +} + +/* + * These attributes are intended for managing TDX module updates. Reading + * them issues a slow, serialized P-SEAMLDR query, so keep them admin-only. + */ +static DEVICE_ATTR_ADMIN_RO(seamldr_version); +static DEVICE_ATTR_ADMIN_RO(num_remaining_updates); + +static struct attribute *seamldr_attrs[] = { + &dev_attr_seamldr_version.attr, + &dev_attr_num_remaining_updates.attr, + NULL, +}; + +static umode_t seamldr_group_visible(struct kobject *kobj, struct attribute *attr, int idx) +{ + const struct tdx_sys_info *sysinfo = tdx_get_sysinfo(); + + if (!sysinfo) + return 0; + + if (!tdx_supports_runtime_update(sysinfo)) + return 0; + + return attr->mode; +} + +static const struct attribute_group seamldr_group = { + .attrs = seamldr_attrs, + .is_visible = seamldr_group_visible, +}; + +static const struct attribute_group *tdx_host_groups[] = { + &tdx_host_group, + &seamldr_group, + NULL, +}; static struct faux_device *fdev; -- 2.52.0