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Message-ID: <CAAhR5DEQw9eMVJ_mWRP3G=XqmsR4_46xh030_Vtyx3HzWXn3wA@mail.gmail.com>
Date: Thu, 30 Oct 2025 16:54:06 -0500
From: Sagi Shahar <sagis@...gle.com>
To: Chao Gao <chao.gao@...el.com>
Cc: linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org, x86@...nel.org,
reinette.chatre@...el.com, ira.weiny@...el.com, kai.huang@...el.com,
dan.j.williams@...el.com, yilun.xu@...ux.intel.com, vannapurve@...gle.com,
paulmck@...nel.org, nik.borisov@...e.com, Farrah Chen <farrah.chen@...el.com>,
"Kirill A. Shutemov" <kas@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v2 07/21] coco/tdx-host: Expose P-SEAMLDR information via sysfs
On Tue, Sep 30, 2025 at 9:55 PM Chao Gao <chao.gao@...el.com> wrote:
>
> 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.
>
> Note that P-SEAMLDR sysfs nodes are hidden when INTEL_TDX_MODULE_UPDATE
> isn't enabled or when P-SEAMLDR isn't loaded by BIOS, both of which
> cause seamldr_get_info() to return NULL.
>
> Signed-off-by: Chao Gao <chao.gao@...el.com>
> Tested-by: Farrah Chen <farrah.chen@...el.com>
> ---
> .../ABI/testing/sysfs-devices-faux-tdx-host | 25 ++++++++
> drivers/virt/coco/tdx-host/tdx-host.c | 63 ++++++++++++++++++-
> 2 files changed, 87 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
Trying to apply this patch locally fails because
sysfs-devices-faux-tdx-host does not exist. There are also conflicts
around drivers/virt/coco/tdx-host/tdx-host.c.
I'm looking at the base commit specified in the cover letter [1] but
even the current head of the tsm/tdx tree [2] doesn't have the
sysfs-devices-faux-tdx-host file. Are there any other dependencies for
this series?
[1] https://git.kernel.org/pub/scm/linux/kernel/git/devsec/tsm.git/commit/?h=tdx&id=9332e088937f
[2] https://git.kernel.org/pub/scm/linux/kernel/git/devsec/tsm.git/tree/Documentation/ABI/testing?h=tdx
> index 18d4a4a71b80..13c1f4f9909c 100644
> --- a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
> +++ b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
> @@ -4,3 +4,28 @@ Description: (RO) Report the version of the loaded TDX module. The TDX module
> version is formatted as x.y.z, where "x" is the major version,
> "y" is the minor version and "z" is the update version. Versions
> are used for bug reporting, TD-Preserving updates and etc.
> +
> +What: /sys/devices/faux/tdx_host/seamldr/version
> +Contact: linux-coco@...ts.linux.dev
> +Description: (RO) Report the version of the loaded SEAM loader. The SEAM
> + loader version is formatted as x.y.z, where "x" is the major
> + version, "y" is the minor version and "z" is the update version.
> + Versions are used for bug reporting and compatibility check.
> +
> +What: /sys/devices/faux/tdx_host/seamldr/num_remaining_updates
> +Contact: linux-coco@...ts.linux.dev
> +Description: (RO) Report the number of remaining updates that can be performed.
> + The CPU keeps track of TCB versions for each TDX Module that
> + has been loaded. Since this tracking database has finite
> + capacity, there's a maximum number of 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 P-SEAMLDR doesn't support updates.
> +
> + See Intel® Trust Domain Extensions - SEAM Loader (SEAMLDR)
> + Interface Specification Chapter 3.3 "SEAMLDR_INFO" and Chapter
> + 4.2 "SEAMLDR.INSTALL" for more information. The documentation is
> + available at:
> + https://cdrdv2-public.intel.com/739045/intel-tdx-seamldr-interface-specification.pdf
> diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
> index 968a19f4e01a..42570c5b221b 100644
> --- a/drivers/virt/coco/tdx-host/tdx-host.c
> +++ b/drivers/virt/coco/tdx-host/tdx-host.c
> @@ -11,6 +11,7 @@
> #include <linux/sysfs.h>
> #include <linux/device/faux.h>
> #include <asm/cpu_device_id.h>
> +#include <asm/seamldr.h>
> #include <asm/tdx.h>
> #include <asm/tdx_global_metadata.h>
>
> @@ -43,7 +44,67 @@ static struct attribute *tdx_host_attrs[] = {
> &dev_attr_version.attr,
> NULL,
> };
> -ATTRIBUTE_GROUPS(tdx_host);
> +
> +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)
> +{
> + const struct seamldr_info *info = seamldr_get_info();
> +
> + if (!info)
> + return -ENXIO;
> +
> + return sysfs_emit(buf, "%u.%u.%u\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)
> +{
> + const struct seamldr_info *info = seamldr_get_info();
> +
> + if (!info)
> + return -ENXIO;
> +
> + return sysfs_emit(buf, "%u\n", info->num_remaining_updates);
> +}
> +
> +/*
> + * Open-code DEVICE_ATTR_RO to specify a different 'show' function for
> + * P-SEAMLDR version as version_show() is used for the TDX Module version.
> + */
> +static struct device_attribute dev_attr_seamldr_version =
> + __ATTR(version, 0444, seamldr_version_show, NULL);
> +static DEVICE_ATTR_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_is_visible(struct kobject *kobj,
> + struct attribute *attr, int n)
> +{
> + return seamldr_get_info() ? attr->mode : 0;
> +}
> +
> +static struct attribute_group seamldr_group = {
> + .name = "seamldr",
> + .attrs = seamldr_attrs,
> + .is_visible = seamldr_group_is_visible,
> +};
> +
> +static const struct attribute_group *tdx_host_groups[] = {
> + &tdx_host_group,
> + &seamldr_group,
> + NULL,
> +};
>
> static int __init tdx_host_init(void)
> {
> --
> 2.47.3
>
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