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x86/tdx: Disable the TDX module during kexec and kdump

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Use the TDH.SYS.DISABLE SEAMCALL, which disables the TDX module,
reclaims all memory resources assigned to TDX, and clears any
partial-write induced poison, to allow kexec and kdump on platforms with
the partial write errata.

On TDX-capable platforms with the partial write erratum, kexec has been
disabled because the new kernel could hit a machine check reading a
previously poisoned memory location.

Later TDX modules support TDH.SYS.DISABLE, which disables the module and
reclaims all TDX memory resources, allowing the new kernel to re-initialize
TDX from scratch. This operation also clears the old memory, cleaning up
any poison.

Add tdx_sys_disable() to tdx_shutdown(), which is called in the
syscore_shutdown path for kexec. This is done just before tdx_shutdown()
disables VMX on all CPUs.

For kdump, call tdx_sys_disable() in the crash path before
x86_virt_emergency_disable_virtualization_cpu() does VMXOFF.

Since this clears any poison on TDX-managed memory, remove the
X86_BUG_TDX_PW_MCE check in machine_kexec() that blocked kexec on
partial write errata platforms.

Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20260402-fuller_tdx_kexec_support-v3-4-34438d7094bf@intel.com
This commit is contained in:
Vishal Verma 2026-04-02 00:32:04 -06:00 committed by Dave Hansen
parent b7d2173946
commit 5b25f249be
3 changed files with 3 additions and 16 deletions
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2
arch/x86/kernel/crash.c
View File

@ -38,6 +38,7 @@
#include <linux/kdebug.h>
#include <asm/cpu.h>
#include <asm/reboot.h>
#include <asm/tdx.h>
#include <asm/intel_pt.h>
#include <asm/crash.h>
#include <asm/cmdline.h>
@ -112,6 +113,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
crash_smp_send_stop();
tdx_sys_disable();
x86_virt_emergency_disable_virtualization_cpu();
/*

16
arch/x86/kernel/machine_kexec_64.c
View File

@ -347,22 +347,6 @@ int machine_kexec_prepare(struct kimage *image)
unsigned long reloc_end = (unsigned long)__relocate_kernel_end;
int result;
/*
* Some early TDX-capable platforms have an erratum. A kernel
* partial write (a write transaction of less than cacheline
* lands at memory controller) to TDX private memory poisons that
* memory, and a subsequent read triggers a machine check.
*
* On those platforms the old kernel must reset TDX private
* memory before jumping to the new kernel otherwise the new
* kernel may see unexpected machine check. For simplicity
* just fail kexec/kdump on those platforms.
*/
if (boot_cpu_has_bug(X86_BUG_TDX_PW_MCE)) {
pr_info_once("Not allowed on platform with tdx_pw_mce bug\n");
return -EOPNOTSUPP;
}
/* Setup the identity mapped 64bit page table */
result = init_pgtable(image, __pa(control_page));
if (result)

1
arch/x86/virt/vmx/tdx/tdx.c
View File

@ -259,6 +259,7 @@ static void tdx_shutdown_cpu(void *ign)
static void tdx_shutdown(void *ign)
{
tdx_sys_disable();
on_each_cpu(tdx_shutdown_cpu, NULL, 1);
}