On Wed, Nov 15, 2023 at 03:00:36PM +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 <[email protected]>
> Reviewed-by: Kai Huang <[email protected]>
> ---
> arch/x86/kernel/relocate_kernel_64.S | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kernel/relocate_kernel_64.S
> b/arch/x86/kernel/relocate_kernel_64.S
> index 56cab1bb25f5..bea89814b48e 100644
> --- a/arch/x86/kernel/relocate_kernel_64.S
> +++ b/arch/x86/kernel/relocate_kernel_64.S
> @@ -145,11 +145,16 @@ 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 "jmp 1f", "", X86_FEATURE_TDX_GUEST
> + orl $X86_CR4_MCE, %eax
> 1:
ALTERNATIVE "", "orl $X86_CR4_MCE, %eax", X86_FEATURE_TDX_GUEST
?
> movq %rax, %cr4
>
> --
> 2.41.0
>
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