On Tue, Jul 08, 2025 at 06:19:03PM -0700, Sohil Mehta wrote:

On 7/7/2025 1:03 AM, Kirill A. Shutemov wrote:

quoted

From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

In order to map the EFI runtime services, set_virtual_address_map()
needs to be called, which resides in the lower half of the address
space. This means that LASS needs to be temporarily disabled around
this call. This can only be done before the CR pinning is set up.

Instead of moving setup_cr_pinning() below efi_enter_virtual_mode() in
arch_cpu_finalize_init(), defer it until core initcall.

Wrapping efi_enter_virtual_mode() into lass_stac()/clac() is not enough
because AC flag gates data accesses, but not instruction fetch. Clearing
the CR4 bit is required.

I think the wording might need to be reordered. How about?

In order to map the EFI runtime services, set_virtual_address_map()
needs to be called, which resides in the lower half of the address
space. This means that LASS needs to be temporarily disabled around
this call.

Wrapping efi_enter_virtual_mode() into lass_stac()/clac() is not enough
because AC flag gates data accesses, but not instruction fetch. Clearing
the CR4 bit is required.

However, this must be done before the CR pinning is set up. Instead of
arbitrarily moving setup_cr_pinning() after efi_enter_virtual_mode() in
arch_cpu_finalize_init(), defer it until core initcall.

Other than that,
Reviewed-by: Sohil Mehta <redacted>

Okay, looks good, thanks!

-- 
  Kiryl Shutsemau / Kirill A. Shutemov