[PATCH 4/4] KVM: x86: Disable the TDX module during kexec and kdump
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: 2026-03-07 01:04:15
Also in:
linux-coco, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Vishal Verma <vishal.l.verma@intel.com> 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, the X86_BUG_TDX_PW_MCE check in machine_kexec() that blocked kexec on partial write errata platforms can be removed. Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> --- arch/x86/kernel/crash.c | 2 ++ arch/x86/kernel/machine_kexec_64.c | 16 ---------------- arch/x86/virt/vmx/tdx/tdx.c | 1 + 3 files changed, 3 insertions(+), 16 deletions(-)
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index cd796818d94d..623d4474631a 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c@@ -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(); /*
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 0590d399d4f1..c3f4a389992d 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c@@ -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)
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 68bd2618dde4..b388fbce5d76 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c@@ -252,6 +252,7 @@ static void tdx_shutdown_cpu(void *ign) static void tdx_shutdown(void *ign) { + tdx_sys_disable(); on_each_cpu(tdx_shutdown_cpu, NULL, 1); }
--
2.53.0