On Tue, 2023-12-05 at 03:45 +0300, Kirill A. Shutemov wrote: > TDX guests are not allowed to clear CR4.MCE. Attempt to clear it leads > to #VE. > > Use alternatives to keep the flag during kexec for TDX guests. > > The change doesn't affect non-TDX-guest environments. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx> > --- > arch/x86/kernel/relocate_kernel_64.S | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S > index 56cab1bb25f5..cd6a53667c6b 100644 > --- a/arch/x86/kernel/relocate_kernel_64.S > +++ b/arch/x86/kernel/relocate_kernel_64.S > @@ -145,12 +145,15 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) > * Set cr4 to a known state: > * - physical address extension enabled > * - 5-level paging, if it was enabled before > + * - Machine check exception on TDX guest. Clearing MCE is not allowed > + * in TDX guests. > */ > movl $X86_CR4_PAE, %eax > testq $X86_CR4_LA57, %r13 > jz 1f > orl $X86_CR4_LA57, %eax > 1: > + ALTERNATIVE "", __stringify(orl $X86_CR4_MCE, %eax), X86_FEATURE_TDX_GUEST > movq %rax, %cr4 > > jmp 1f Nit: It seems <asm/alternative.h> isn't included in relocate_kernel_64.S. Maybe it's better to do it explicitly. Maybe even better to explicitly include <linux/stringify.h> too, but I see <asm/alternative.h> already does that. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
