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

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

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index cd796818d94d9ef11ea51f95990704a14bb0bafc..623d4474631a6586515cfebc6cdc7433963e47a9 100644 (file)
--- 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 0590d399d4f1f645c171426f52065f7c96c2a99e..c3f4a389992daaa0e899a1889b9684d8ed37528f 100644 (file)
--- 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 1ae558bcca3a537e54f3ea0427725637320ab4d9..c0c6281b08a5e19d88d821373a40d3785028512f 100644 (file)
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -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);
 }