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x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs

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The hypervisor is an untrusted entity for TDX guests. It cannot be used
to boot secondary CPUs. The function hv_vtl_wakeup_secondary_cpu() cannot
be used.

Instead, the virtual firmware boots the secondary CPUs and places them in
a state to transfer control to the kernel using the wakeup mailbox. The
firmware enumerates the mailbox via either an ACPI table or a DeviceTree
node.

If the wakeup mailbox is present, the kernel updates the APIC callback
wakeup_secondary_cpu_64() to use it.

Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Dexuan Cui <dexuan@kernel.org>
This commit is contained in:
Ricardo Neri 2026-03-04 15:41:21 -08:00 committed by Dexuan Cui
parent 8020034119
commit 7a035678fc
1 changed files with 9 additions and 1 deletions
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10
arch/x86/hyperv/hv_vtl.c
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@ -274,7 +274,15 @@ int __init hv_vtl_early_init(void)
panic("XSAVE has to be disabled as it is not supported by this module.\n"
"Please add 'noxsave' to the kernel command line.\n");
apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
/*
* TDX confidential VMs do not trust the hypervisor and cannot use it to
* boot secondary CPUs. Instead, they will be booted using the wakeup
* mailbox if detected during boot. See setup_arch().
*
* There is no paravisor present if we are here.
*/
if (!hv_isolation_type_tdx())
apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
return 0;
}