Replace the #include of <linux/mod_devicetable.h> by the more specific
<linux/device-id/*.h> where applicable. For most cases the include
can be dropped completely, only a few drivers need one or two headers
added.
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/1a3f2007c5c5dcf555c09a4035ce3ae8ef1b6c49.1782808461.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>
The TDX module version is currently stashed in some global variables
and dumped out to sysfs without locking. This works fine when the
version is static and never changes.
But with runtime module updates, the TDX module version can change.
Some kind of locking is needed. Barring this, userspace could
theoretically see a strange torn module version that is some
Frankenstein version from from two different updates.
Use the new module update lock/unlock to prevent updates while
trying to read the version.
Don't be fussy about it. There's no need to snapshot the version or do
READ_ONCE(), or minimize lock holding times. sysfs_emit() does not
sleep. Also note that the lock/unlock are backed by
preempt_dis/enable() which are really cheap CPU-local operations.
This is not a heavyweight lock.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
tl;dr: Select fw_upload for doing TDX module updates. The process of
selecting among available update images is complicated and nuanced. Punt
the selection process out to userspace. One existing userspace
implementation today is the script in the Intel TDX Module Binaries
repository[1].
Long Version:
The kernel supports two primary firmware update mechanisms:
1. request_firmware() - used by microcode, SEV firmware, hundreds of
other drivers
2. 'struct fw_upload' - used by CXL, FPGA updates, dozens of others
The key difference between is that request_firmware() loads a named file
from the filesystem where the filename is kernel-controlled, while
fw_upload accepts firmware data directly from userspace.
TDX module firmware update selection policy is too complex for the kernel.
Leave it to userspace and use fw_upload.
Add a skeleton fw_upload implementation to be fleshed out in subsequent
patches.
Refactor the sysfs visiblity attribute function so it can be used as a
more generic flag for the presence of viable runtime update support.
Why fw_upload instead of request_firmware()?
============================================
Selecting a TDX module update image is not a simple "load the latest"
decision. Userspace needs to choose an image that is compatible with both
the platform and the currently running module.
Some constraints are hard requirements:
a. Module version series are platform-specific. For example, the 1.5.x
series runs on Sapphire Rapids but not Granite Rapids, which needs
2.0.x.
b. Updates are also constrained by version distance. A 1.5.6 module
might permit updates to 1.5.7 but not to 1.5.50.
There may also be userspace policy choices:
c. Decide the update direction: upgrade or downgrade
d. Choose whether to optimize for fewer updates or smaller version
steps, for example, 1.2.3=>1.2.5 versus 1.2.3=>1.2.4=>1.2.5.
Given that complexity, leave module selection to userspace and use
fw_upload.
1. https://github.com/intel/confidential-computing.tdx.tdx-module.binaries/blob/main/version_select_and_load.py
[ dhansen: add version script link, add more explanation of code moves,
fix some minor whitespace issues ]
Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Link: https://lore.kernel.org/kvm/01fc8946-eb84-46fa-9458-f345dd3f6033@intel.com/
Link: https://patch.msgid.link/20260520133909.409394-13-chao.gao@intel.com
TDX-capable CPUs clobber the current VMCS on P-SEAMLDR calls. Clearing
the current VMCS behind KVM's back breaks KVM.
Future CPUs will fix this by preserving the current VMCS across
P-SEAMLDR calls. A future specification update will describe the
VMCS-clearing behavior as an erratum and to state that it does not
occur when IA32_VMX_BASIC[60] is set.
Add a CPU bug bit and refuse to expose P-SEAMLDR information on
affected CPUs.
Use a CPU bug bit to stay consistent with X86_BUG_TDX_PW_MCE. As a
bonus, the bug bit is visible to userspace, which allows userspace to
determine why these sysfs files are not exposed, and it can also be
checked by other kernel components in the future if needed.
== Alternatives ==
Two workarounds were considered but both were rejected:
1. Save/restore the current VMCS around P-SEAMLDR calls. This produces ugly
assembly code [1] and doesn't play well with #MCE or #NMI if they
need to use the current VMCS.
2. Move KVM's VMCS tracking logic to the TDX core code, which would break
the boundary between KVM and the TDX core code [2].
[ dhansen: comment and changelog munging. Add seamldr_call() bug check. ]
Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/kvm/fedb3192-e68c-423c-93b2-a4dc2f964148@intel.com/ # [1]
Link: https://lore.kernel.org/kvm/aYIXFmT-676oN6j0@google.com/ # [2]
Link: https://patch.msgid.link/20260520133909.409394-12-chao.gao@intel.com
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 visible only when updates
are supported.
Note that the underlying P-SEAMLDR attributes are available regardless
of update support; this only restricts their visibility to userspace.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260520133909.409394-11-chao.gao@intel.com
For TDX module updates, userspace needs to select compatible update
versions based on the current module version.
For example, the 1.5.x series runs on Sapphire Rapids but not Granite
Rapids, which needs 2.0.x. Updates are also constrained by version
distance, so a 1.5.6 module might permit updates to 1.5.7 but not to
1.5.20.
Start the process of punting the version selection logic to userspace.
Expose the TDX module version in the new faux device.
Define TDX_VERSION_FMT macro for the TDX version format since it will be
used multiple times. Also convert an existing print statement to use it.
== Background ==
For posterity, here's what other firmware mechanisms do:
1. AMD SEV leverages an existing PCI device for the PSP to expose
metadata. TDX uses a faux device as it doesn't have PCI device
in its architecture.
2. Microcode uses per-CPU virtual devices to report microcode revisions
because CPUs can have different revisions. But, there is only a
single TDX module, so exposing the TDX module version through a global
TDX faux device is appropriate
3. ARM's CCA implementation isn't in-tree yet, but will likely follow a
similar faux device approach, though it's unclear whether they need
to expose firmware version information
[ dhansen: trim changelog ]
Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh/ # [1]
Link: https://patch.msgid.link/20260520133909.409394-8-chao.gao@intel.com
TDX depends on a platform firmware module that runs on the CPU.
Unlike other CoCo architectures, TDX has no hardware "device"
running the show, just a blob on the CPU.
Create a virtual device to anchor interactions with this platform
firmware. This lets later code:
- expose metadata: TDX module version, seamldr version, to userspace
as device attributes
- implement firmware uploader APIs (which are tied to a device) to
support TDX module runtime updates
Use a faux device because the TDX module is singular within the system
and has no 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].
Thanks to Dan and Yilun for all the help on this one.
[ dhansen: trim changelog ]
Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh/ # [1]
Link: https://patch.msgid.link/20260520133909.409394-7-chao.gao@intel.com
