On Tue, Dec 05, 2023 at 11:58:45PM +0000, Huang, Kai wrote: > 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. Okay, I will add both. -- Kiryl Shutsemau / Kirill A. Shutemov _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
