We can either BUG(), or say "TDX is broken and please reboot the machine". Removal has already handled by BIOS so the kernel cannot reject it. For CPU hot-removal, when the kernel receives this event, the CPU hot. Specifically, for CPU hot-add, we can print error message and reject the newĬPU. On TDX enabled platform, we print out error message saying it is a BIOS bug. Is enabled by BIOS (patch 01 in this series), and when ACPI CPU hotplug happens
#Need driver for mbox 2 code
So I think the proper way to handle is: we still have code to detect whether TDX Related to whether TDX is enabled in BIOS, no matter whether the TDX module has This means if TDX is enabled in BIOS, a non-buggy BIOS should never deliver ACPIĬPU hotplug event to kernel, otherwise it is a BIOS bug. TheīIOS should prevent CPUs from being hot-added or hot-removed after platform "TDX doesn’t support adding or removing CPUs from TDX security perimeter. Could you give someĪfter discussion with TDX guys, they have agreed they will add below to either
#Need driver for mbox 2 how to
Trying to close how to handle ACPI CPU hotplug for TDX. > when CPU hot-removal, so I just used BUG() in assumption that TDX isn't safe to > because there's no architectural specification regarding to the behaviour of TDX
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> 1) this basically on a theoretical problem and shouldn't happen in practice 2) > Regarding to the code change, I agree the BUG() isn't good.
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I guess this is the best thing we can do. > to the TDX and CPU hotplug interaction to the BIOS write guide and make it > At the meantime, I am pushing Intel internally to add some statements regarding > architecture feature", so Intel doesn't have an architectural specification for > Also, I was told "CPU hot-plug is a system feature, not a CPU feature or Intel > But theoretically, the BIOS isn't in TDX's TCB, and can be from 3rd party. > the kernel, so if kernel receives such event, it should be fair enough to treat > got from Intel internally is a non-buggy BIOS should never report such event to > ACPI CPU hot-plug event, or if BIOS gets the event, will it suppress it. For instance, whether BIOS will ever get the > Unfortunately there's no public spec mentioning what's the behaviour of ACPI CPU > otherwise the further step of TDX module initialization will fail. > the platform has (such as such as and ),
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> 2) Also some SEAMCALLs must be called on all logical CPUs or CPU packages that Please see "3.4 SEAMLDR_SEAMINFO" in the P. > packages and total logical cpus at some location of SEAMRR so it can later be > they are TDX compatible, and it keeps some information, such as total CPU > 1) During platform boot MCHECK verifies all logical CPUs on all packages that The public specs doesn't explicitly say it, but it is > TDX doesn't support ACPI CPU hotplug (both hot-add and hot-removal) is an > This doesn't seem like something the kernel should be doing unilaterally. > the kernel goes boom, are the firmware folks going to cry "Kernel bug!!"?
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> told the firmware guys about this? Is this in a spec somewhere? When > incompatible and even BUG()'ing if we see them together. > So, the kernel is now declaring ACPI CPU hotplug and TDX to be > the kernel cannot continue to work normally, and BUG(). For hot-removal, for simplicity just assume For ACPI CPU hot-add, the kernel should speak out this is a BIOS > If the kernel ever receives ACPI CPU hotplug event, it is likely a BIOS > include Intel platforms which support Intel Trust Domain Extensions > CPU hotplug when such technology is enabled by the BIOS. > Platforms with confidential computing technology may not support ACPI > On Fri, at 11:57 -0700, Dave Hansen wrote: To: Dave Hansen Re: cc_platform: Add new attribute to prevent ACPI CPU hotplugĭate: Wed, 23:09:27 +1200 Re: cc_platform: Add new attribute to prevent ACPI CPU hotplug - Kai Huang All of help / color / mirror / Atom feed From: Kai Huang